Processes can yield the entire process

[akaros.git] / kern / src / process.c

/* Copyright (c) 2009, 2010 The Regents of the University of California
 * Barret Rhoden <brho@cs.berkeley.edu>
 * See LICENSE for details. */

#ifdef __SHARC__
#pragma nosharc
#endif

#include <ros/bcq.h>
#include <event.h>
#include <arch/arch.h>
#include <bitmask.h>
#include <process.h>
#include <atomic.h>
#include <smp.h>
#include <pmap.h>
#include <trap.h>
#include <schedule.h>
#include <manager.h>
#include <stdio.h>
#include <assert.h>
#include <time.h>
#include <hashtable.h>
#include <slab.h>
#include <sys/queue.h>
#include <frontend.h>
#include <monitor.h>
#include <resource.h>
#include <elf.h>
#include <arsc_server.h>
#include <devfs.h>

/* Process Lists */
struct proc_list proc_runnablelist = TAILQ_HEAD_INITIALIZER(proc_runnablelist);
spinlock_t runnablelist_lock = SPINLOCK_INITIALIZER;
struct kmem_cache *proc_cache;

/* Tracks which cores are idle, similar to the vcoremap.  Each value is the
 * physical coreid of an unallocated core. */
spinlock_t idle_lock = SPINLOCK_INITIALIZER;
uint32_t LCKD(&idle_lock) (RO idlecoremap)[MAX_NUM_CPUS];
uint32_t LCKD(&idle_lock) num_idlecores = 0;
uint32_t num_mgmtcores = 1;

/* Helper function to return a core to the idlemap.  It causes some more lock
 * acquisitions (like in a for loop), but it's a little easier.  Plus, one day
 * we might be able to do this without locks (for the putting). */
void put_idle_core(uint32_t coreid)
{
        spin_lock(&idle_lock);
        idlecoremap[num_idlecores++] = coreid;
        spin_unlock(&idle_lock);
}

/* Other helpers, implemented later. */
static void __proc_startcore(struct proc *p, trapframe_t *tf);
static bool is_mapped_vcore(struct proc *p, uint32_t pcoreid);
static uint32_t get_vcoreid(struct proc *p, uint32_t pcoreid);
static uint32_t get_pcoreid(struct proc *p, uint32_t vcoreid);
static void __proc_free(struct kref *kref);

/* PID management. */
#define PID_MAX 32767 // goes from 0 to 32767, with 0 reserved
static DECL_BITMASK(pid_bmask, PID_MAX + 1);
spinlock_t pid_bmask_lock = SPINLOCK_INITIALIZER;
struct hashtable *pid_hash;
spinlock_t pid_hash_lock; // initialized in proc_init

/* Finds the next free entry (zero) entry in the pid_bitmask.  Set means busy.
 * PID 0 is reserved (in proc_init).  A return value of 0 is a failure (and
 * you'll also see a warning, for now).  Consider doing this with atomics. */
static pid_t get_free_pid(void)
{
        static pid_t next_free_pid = 1;
        pid_t my_pid = 0;

        spin_lock(&pid_bmask_lock);
        // atomically (can lock for now, then change to atomic_and_return
        FOR_CIRC_BUFFER(next_free_pid, PID_MAX + 1, i) {
                // always points to the next to test
                next_free_pid = (next_free_pid + 1) % (PID_MAX + 1);
                if (!GET_BITMASK_BIT(pid_bmask, i)) {
                        SET_BITMASK_BIT(pid_bmask, i);
                        my_pid = i;
                        break;
                }
        }
        spin_unlock(&pid_bmask_lock);
        if (!my_pid)
                warn("Shazbot!  Unable to find a PID!  You need to deal with this!\n");
        return my_pid;
}

/* Return a pid to the pid bitmask */
static void put_free_pid(pid_t pid)
{
        spin_lock(&pid_bmask_lock);
        CLR_BITMASK_BIT(pid_bmask, pid);
        spin_unlock(&pid_bmask_lock);
}

/* While this could be done with just an assignment, this gives us the
 * opportunity to check for bad transitions.  Might compile these out later, so
 * we shouldn't rely on them for sanity checking from userspace.  */
int __proc_set_state(struct proc *p, uint32_t state)
{
        uint32_t curstate = p->state;
        /* Valid transitions:
         * C   -> RBS
         * C   -> D
         * RBS -> RGS
         * RGS -> RBS
         * RGS -> W
         * RGM -> W
         * W   -> RBS
         * W   -> RBM
         * RGS -> RBM
         * RBM -> RGM
         * RGM -> RBM
         * RGM -> RBS
         * RGS -> D
         * RGM -> D
         *
         * These ought to be implemented later (allowed, not thought through yet).
         * RBS -> D
         * RBM -> D
         */
        #if 1 // some sort of correctness flag
        switch (curstate) {
                case PROC_CREATED:
                        if (!(state & (PROC_RUNNABLE_S | PROC_DYING)))
                                panic("Invalid State Transition! PROC_CREATED to %02x", state);
                        break;
                case PROC_RUNNABLE_S:
                        if (!(state & (PROC_RUNNING_S | PROC_DYING)))
                                panic("Invalid State Transition! PROC_RUNNABLE_S to %02x", state);
                        break;
                case PROC_RUNNING_S:
                        if (!(state & (PROC_RUNNABLE_S | PROC_RUNNABLE_M | PROC_WAITING |
                                       PROC_DYING)))
                                panic("Invalid State Transition! PROC_RUNNING_S to %02x", state);
                        break;
                case PROC_WAITING:
                        if (!(state & (PROC_RUNNABLE_S | PROC_RUNNABLE_M)))
                                panic("Invalid State Transition! PROC_WAITING to %02x", state);
                        break;
                case PROC_DYING:
                        if (state != PROC_CREATED) // when it is reused (TODO)
                                panic("Invalid State Transition! PROC_DYING to %02x", state);
                        break;
                case PROC_RUNNABLE_M:
                        if (!(state & (PROC_RUNNING_M | PROC_DYING)))
                                panic("Invalid State Transition! PROC_RUNNABLE_M to %02x", state);
                        break;
                case PROC_RUNNING_M:
                        if (!(state & (PROC_RUNNABLE_S | PROC_RUNNABLE_M | PROC_WAITING |
                                       PROC_DYING)))
                                panic("Invalid State Transition! PROC_RUNNING_M to %02x", state);
                        break;
        }
        #endif
        p->state = state;
        return 0;
}

/* Returns a pointer to the proc with the given pid, or 0 if there is none.
 * This uses get_not_zero, since it is possible the refcnt is 0, which means the
 * process is dying and we should not have the ref (and thus return 0).  We need
 * to lock to protect us from getting p, (someone else removes and frees p),
 * then get_not_zero() on p.
 * Don't push the locking into the hashtable without dealing with this. */
struct proc *pid2proc(pid_t pid)
{
        spin_lock(&pid_hash_lock);
        struct proc *p = hashtable_search(pid_hash, (void*)pid);
        if (p)
                if (!kref_get_not_zero(&p->p_kref, 1))
                        p = 0;
        spin_unlock(&pid_hash_lock);
        return p;
}

/* Performs any initialization related to processes, such as create the proc
 * cache, prep the scheduler, etc.  When this returns, we should be ready to use
 * any process related function. */
void proc_init(void)
{
        /* Catch issues with the vcoremap and TAILQ_ENTRY sizes */
        static_assert(sizeof(TAILQ_ENTRY(vcore)) == sizeof(void*) * 2);
        proc_cache = kmem_cache_create("proc", sizeof(struct proc),
                     MAX(HW_CACHE_ALIGN, __alignof__(struct proc)), 0, 0, 0);
        /* Init PID mask and hash.  pid 0 is reserved. */
        SET_BITMASK_BIT(pid_bmask, 0);
        spinlock_init(&pid_hash_lock);
        spin_lock(&pid_hash_lock);
        pid_hash = create_hashtable(100, __generic_hash, __generic_eq);
        spin_unlock(&pid_hash_lock);
        schedule_init();
        /* Init idle cores. Core 0 is the management core. */
        spin_lock(&idle_lock);
#ifdef __CONFIG_DISABLE_SMT__
        /* assumes core0 is the only management core (NIC and monitor functionality
         * are run there too.  it just adds the odd cores to the idlecoremap */
        assert(!(num_cpus % 2));
        // TODO: consider checking x86 for machines that actually hyperthread
        num_idlecores = num_cpus >> 1;
#ifdef __CONFIG_ARSC_SERVER__
        // Dedicate one core (core 2) to sysserver, might be able to share wit NIC
        num_mgmtcores++;
        assert(num_cpus >= num_mgmtcores);
        send_kernel_message(2, (amr_t)arsc_server, 0,0,0, KMSG_ROUTINE);
#endif
        for (int i = 0; i < num_idlecores; i++)
                idlecoremap[i] = (i * 2) + 1;
#else
        // __CONFIG_DISABLE_SMT__
        #ifdef __CONFIG_NETWORKING__
        num_mgmtcores++; // Next core is dedicated to the NIC
        assert(num_cpus >= num_mgmtcores);
        #endif
        #ifdef __CONFIG_APPSERVER__
        #ifdef __CONFIG_DEDICATED_MONITOR__
        num_mgmtcores++; // Next core dedicated to running the kernel monitor
        assert(num_cpus >= num_mgmtcores);
        // Need to subtract 1 from the num_mgmtcores # to get the cores index
        send_kernel_message(num_mgmtcores-1, (amr_t)monitor, 0,0,0, KMSG_ROUTINE);
        #endif
        #endif
#ifdef __CONFIG_ARSC_SERVER__
        // Dedicate one core (core 2) to sysserver, might be able to share wit NIC
        num_mgmtcores++;
        assert(num_cpus >= num_mgmtcores);
        send_kernel_message(num_mgmtcores-1, (amr_t)arsc_server, 0,0,0, KMSG_ROUTINE);
#endif
        num_idlecores = num_cpus - num_mgmtcores;
        for (int i = 0; i < num_idlecores; i++)
                idlecoremap[i] = i + num_mgmtcores;
#endif /* __CONFIG_DISABLE_SMT__ */

        spin_unlock(&idle_lock);
        atomic_init(&num_envs, 0);
}

/* Be sure you init'd the vcore lists before calling this. */
static void proc_init_procinfo(struct proc* p)
{
        p->procinfo->pid = p->pid;
        p->procinfo->ppid = p->ppid;
        // TODO: maybe do something smarter here
#ifdef __CONFIG_DISABLE_SMT__
        p->procinfo->max_vcores = num_cpus >> 1;
#else
        p->procinfo->max_vcores = MAX(1,num_cpus-num_mgmtcores);
#endif /* __CONFIG_DISABLE_SMT__ */
        p->procinfo->tsc_freq = system_timing.tsc_freq;
        p->procinfo->heap_bottom = (void*)UTEXT;
        /* 0'ing the arguments.  Some higher function will need to set them */
        memset(p->procinfo->argp, 0, sizeof(p->procinfo->argp));
        memset(p->procinfo->argbuf, 0, sizeof(p->procinfo->argbuf));
        /* 0'ing the vcore/pcore map.  Will link the vcores later. */
        memset(&p->procinfo->vcoremap, 0, sizeof(p->procinfo->vcoremap));
        memset(&p->procinfo->pcoremap, 0, sizeof(p->procinfo->pcoremap));
        p->procinfo->num_vcores = 0;
        p->procinfo->coremap_seqctr = SEQCTR_INITIALIZER;
        /* For now, we'll go up to the max num_cpus (at runtime).  In the future,
         * there may be cases where we can have more vcores than num_cpus, but for
         * now we'll leave it like this. */
        for (int i = 0; i < num_cpus; i++) {
                TAILQ_INSERT_TAIL(&p->inactive_vcs, &p->procinfo->vcoremap[i], list);
        }
}

static void proc_init_procdata(struct proc *p)
{
        memset(p->procdata, 0, sizeof(struct procdata));
}

/* Allocates and initializes a process, with the given parent.  Currently
 * writes the *p into **pp, and returns 0 on success, < 0 for an error.
 * Errors include:
 *  - ENOFREEPID if it can't get a PID
 *  - ENOMEM on memory exhaustion */
error_t proc_alloc(struct proc **pp, struct proc *parent)
{
        error_t r;
        struct proc *p;

        if (!(p = kmem_cache_alloc(proc_cache, 0)))
                return -ENOMEM;

        { INITSTRUCT(*p)

        /* one reference for the proc existing, and one for the ref we pass back. */
        kref_init(&p->p_kref, __proc_free, 2);
        // Setup the default map of where to get cache colors from
        p->cache_colors_map = global_cache_colors_map;
        p->next_cache_color = 0;
        /* Initialize the address space */
        if ((r = env_setup_vm(p)) < 0) {
                kmem_cache_free(proc_cache, p);
                return r;
        }
        if (!(p->pid = get_free_pid())) {
                kmem_cache_free(proc_cache, p);
                return -ENOFREEPID;
        }
        /* Set the basic status variables. */
        spinlock_init(&p->proc_lock);
        p->exitcode = 1337;     /* so we can see processes killed by the kernel */
        p->ppid = parent ? parent->pid : 0;
        p->state = PROC_CREATED; /* shouldn't go through state machine for init */
        p->is_mcp = FALSE;
        p->env_flags = 0;
        p->env_entry = 0; // cheating.  this really gets set later
        p->heap_top = (void*)UTEXT;     /* heap_bottom set in proc_init_procinfo */
        memset(&p->resources, 0, sizeof(p->resources));
        memset(&p->env_ancillary_state, 0, sizeof(p->env_ancillary_state));
        memset(&p->env_tf, 0, sizeof(p->env_tf));
        spinlock_init(&p->mm_lock);
        TAILQ_INIT(&p->vm_regions); /* could init this in the slab */
        /* Initialize the vcore lists, we'll build the inactive list so that it includes
         * all vcores when we initialize procinfo.  Do this before initing procinfo. */
        TAILQ_INIT(&p->online_vcs);
        TAILQ_INIT(&p->bulk_preempted_vcs);
        TAILQ_INIT(&p->inactive_vcs);
        /* Init procinfo/procdata.  Procinfo's argp/argb are 0'd */
        proc_init_procinfo(p);
        proc_init_procdata(p);

        /* Initialize the generic sysevent ring buffer */
        SHARED_RING_INIT(&p->procdata->syseventring);
        /* Initialize the frontend of the sysevent ring buffer */
        FRONT_RING_INIT(&p->syseventfrontring,
                        &p->procdata->syseventring,
                        SYSEVENTRINGSIZE);

        /* Init FS structures TODO: cleanup (might pull this out) */
        kref_get(&default_ns.kref, 1);
        p->ns = &default_ns;
        spinlock_init(&p->fs_env.lock);
        p->fs_env.umask = parent ? parent->fs_env.umask : S_IWGRP | S_IWOTH;
        p->fs_env.root = p->ns->root->mnt_root;
        kref_get(&p->fs_env.root->d_kref, 1);
        p->fs_env.pwd = parent ? parent->fs_env.pwd : p->fs_env.root;
        kref_get(&p->fs_env.pwd->d_kref, 1);
        memset(&p->open_files, 0, sizeof(p->open_files));       /* slightly ghetto */
        spinlock_init(&p->open_files.lock);
        p->open_files.max_files = NR_OPEN_FILES_DEFAULT;
        p->open_files.max_fdset = NR_FILE_DESC_DEFAULT;
        p->open_files.fd = p->open_files.fd_array;
        p->open_files.open_fds = (struct fd_set*)&p->open_files.open_fds_init;
        /* Init the ucq hash lock */
        p->ucq_hashlock = (struct hashlock*)&p->ucq_hl_noref;
        hashlock_init(p->ucq_hashlock, HASHLOCK_DEFAULT_SZ);

        atomic_inc(&num_envs);
        frontend_proc_init(p);
        printd("[%08x] new process %08x\n", current ? current->pid : 0, p->pid);
        } // INIT_STRUCT
        *pp = p;
        return 0;
}

/* We have a bunch of different ways to make processes.  Call this once the
 * process is ready to be used by the rest of the system.  For now, this just
 * means when it is ready to be named via the pidhash.  In the future, we might
 * push setting the state to CREATED into here. */
void __proc_ready(struct proc *p)
{
        spin_lock(&pid_hash_lock);
        hashtable_insert(pid_hash, (void*)p->pid, p);
        spin_unlock(&pid_hash_lock);
}

/* Creates a process from the specified file, argvs, and envps.  Tempted to get
 * rid of proc_alloc's style, but it is so quaint... */
struct proc *proc_create(struct file *prog, char **argv, char **envp)
{
        struct proc *p;
        error_t r;
        if ((r = proc_alloc(&p, current)) < 0)
                panic("proc_create: %e", r);    /* one of 3 quaint usages of %e */
        procinfo_pack_args(p->procinfo, argv, envp);
        assert(load_elf(p, prog) == 0);
        /* Connect to stdin, stdout, stderr */
        assert(insert_file(&p->open_files, dev_stdin,  0) == 0);
        assert(insert_file(&p->open_files, dev_stdout, 0) == 1);
        assert(insert_file(&p->open_files, dev_stderr, 0) == 2);
        __proc_ready(p);
        return p;
}

/* This is called by kref_put(), once the last reference to the process is
 * gone.  Don't call this otherwise (it will panic).  It will clean up the
 * address space and deallocate any other used memory. */
static void __proc_free(struct kref *kref)
{
        struct proc *p = container_of(kref, struct proc, p_kref);
        physaddr_t pa;

        printd("[PID %d] freeing proc: %d\n", current ? current->pid : 0, p->pid);
        // All parts of the kernel should have decref'd before __proc_free is called
        assert(kref_refcnt(&p->p_kref) == 0);

        kref_put(&p->fs_env.root->d_kref);
        kref_put(&p->fs_env.pwd->d_kref);
        destroy_vmrs(p);
        frontend_proc_free(p);  /* TODO: please remove me one day */
        /* Free any colors allocated to this process */
        if (p->cache_colors_map != global_cache_colors_map) {
                for(int i = 0; i < llc_cache->num_colors; i++)
                        cache_color_free(llc_cache, p->cache_colors_map);
                cache_colors_map_free(p->cache_colors_map);
        }
        /* Remove us from the pid_hash and give our PID back (in that order). */
        spin_lock(&pid_hash_lock);
        if (!hashtable_remove(pid_hash, (void*)p->pid))
                panic("Proc not in the pid table in %s", __FUNCTION__);
        spin_unlock(&pid_hash_lock);
        put_free_pid(p->pid);
        /* Flush all mapped pages in the user portion of the address space */
        env_user_mem_free(p, 0, UVPT);
        /* These need to be free again, since they were allocated with a refcnt. */
        free_cont_pages(p->procinfo, LOG2_UP(PROCINFO_NUM_PAGES));
        free_cont_pages(p->procdata, LOG2_UP(PROCDATA_NUM_PAGES));

        env_pagetable_free(p);
        p->env_pgdir = 0;
        p->env_cr3 = 0;

        atomic_dec(&num_envs);

        /* Dealloc the struct proc */
        kmem_cache_free(proc_cache, p);
}

/* Whether or not actor can control target.  Note we currently don't need
 * locking for this. TODO: think about that, esp wrt proc's dying. */
bool proc_controls(struct proc *actor, struct proc *target)
{
        return ((actor == target) || (target->ppid == actor->pid));
}

/* Helper to incref by val.  Using the helper to help debug/interpose on proc
 * ref counting.  Note that pid2proc doesn't use this interface. */
void proc_incref(struct proc *p, unsigned int val)
{
        kref_get(&p->p_kref, val);
}

/* Helper to decref for debugging.  Don't directly kref_put() for now. */
void proc_decref(struct proc *p)
{
        kref_put(&p->p_kref);
}

/* Helper, makes p the 'current' process, dropping the old current/cr3.  Don't
 * incref - this assumes the passed in reference already counted 'current'. */
static void __set_proc_current(struct proc *p)
{
        /* We use the pcpui to access 'current' to cut down on the core_id() calls,
         * though who know how expensive/painful they are. */
        struct per_cpu_info *pcpui = &per_cpu_info[core_id()];
        /* If the process wasn't here, then we need to load its address space. */
        if (p != pcpui->cur_proc) {
                /* Do not incref here.  We were given the reference to current,
                 * pre-upped. */
                lcr3(p->env_cr3);
                /* This is "leaving the process context" of the previous proc.  The
                 * previous lcr3 unloaded the previous proc's context.  This should
                 * rarely happen, since we usually proactively leave process context,
                 * but this is the fallback. */
                if (pcpui->cur_proc)
                        proc_decref(pcpui->cur_proc);
                pcpui->cur_proc = p;
        }
}

/* Dispatches a process to run, either on the current core in the case of a
 * RUNNABLE_S, or on its partition in the case of a RUNNABLE_M.  This should
 * never be called to "restart" a core.  This expects that the "instructions"
 * for which core(s) to run this on will be in the vcoremap, which needs to be
 * set externally.
 *
 * When a process goes from RUNNABLE_M to RUNNING_M, its vcoremap will be
 * "packed" (no holes in the vcore->pcore mapping), vcore0 will continue to run
 * it's old core0 context, and the other cores will come in at the entry point.
 * Including in the case of preemption.
 *
 * This won't return if the current core is going to be one of the processes
 * cores (either for _S mode or for _M if it's in the vcoremap).  proc_run will
 * eat your reference if it does not return. */
void proc_run(struct proc *p)
{
        bool self_ipi_pending = FALSE;
        struct vcore *vc_i;
        spin_lock(&p->proc_lock);

        switch (p->state) {
                case (PROC_DYING):
                        spin_unlock(&p->proc_lock);
                        printk("Process %d not starting due to async death\n", p->pid);
                        // if we're a worker core, smp_idle, o/w return
                        if (!management_core())
                                smp_idle(); // this never returns
                        return;
                case (PROC_RUNNABLE_S):
                        assert(current != p);
                        __proc_set_state(p, PROC_RUNNING_S);
                        /* We will want to know where this process is running, even if it is
                         * only in RUNNING_S.  can use the vcoremap, which makes death easy.
                         * Also, this is the signal used in trap.c to know to save the tf in
                         * env_tf. */
                        __seq_start_write(&p->procinfo->coremap_seqctr);
                        p->procinfo->num_vcores = 0;    /* TODO (VC#) */
                        /* TODO: For now, we won't count this as an active vcore (on the
                         * lists).  This gets unmapped in resource.c, and needs work. */
                        __map_vcore(p, 0, core_id()); // sort of.  this needs work.
                        __seq_end_write(&p->procinfo->coremap_seqctr);
                        /* __set_proc_current assumes the reference we give it is for
                         * current.  Decref if current is already properly set, otherwise
                         * ensure current is set. */
                        if (p == current)
                                proc_decref(p);
                        else
                                __set_proc_current(p);
                        /* We restartcore, instead of startcore, since startcore is a bit
                         * lower level and we want a chance to process kmsgs before starting
                         * the process. */
                        spin_unlock(&p->proc_lock);
                        current_tf = &p->env_tf;
                        proc_restartcore();
                        break;
                case (PROC_RUNNABLE_M):
                        /* vcoremap[i] holds the coreid of the physical core allocated to
                         * this process.  It is set outside proc_run.  For the kernel
                         * message, a0 = struct proc*, a1 = struct trapframe*.   */
                        if (p->procinfo->num_vcores) {
                                __proc_set_state(p, PROC_RUNNING_M);
                                /* Up the refcnt, since num_vcores are going to start using this
                                 * process and have it loaded in their 'current'. */
                                proc_incref(p, p->procinfo->num_vcores);
                                /* If the core we are running on is in the vcoremap, we will get
                                 * an IPI (once we reenable interrupts) and never return. */
                                if (is_mapped_vcore(p, core_id()))
                                        self_ipi_pending = TRUE;
                                /* Send kernel messages to all online vcores (which were added
                                 * to the list and mapped in __proc_give_cores()), making them
                                 * turn online */
                                TAILQ_FOREACH(vc_i, &p->online_vcs, list) {
                                        send_kernel_message(vc_i->pcoreid, __startcore, (long)p,
                                                            0, 0, KMSG_ROUTINE);
                                }
                        } else {
                                warn("Tried to proc_run() an _M with no vcores!");
                        }
                        /* Unlock and decref/wait for the IPI if one is pending.  This will
                         * eat the reference if we aren't returning.
                         *
                         * There a subtle race avoidance here.  __proc_startcore can handle
                         * a death message, but we can't have the startcore come after the
                         * death message.  Otherwise, it would look like a new process.  So
                         * we hold the lock til after we send our message, which prevents a
                         * possible death message.
                         * - Note there is no guarantee this core's interrupts were on, so
                         *   it may not get the message for a while... */
                        spin_unlock(&p->proc_lock);
                        __proc_kmsg_pending(p, self_ipi_pending);
                        break;
                default:
                        spin_unlock(&p->proc_lock);
                        panic("Invalid process state %p in proc_run()!!", p->state);
        }
}

/* Actually runs the given context (trapframe) of process p on the core this
 * code executes on.  This is called directly by __startcore, which needs to
 * bypass the routine_kmsg check.  Interrupts should be off when you call this.
 *
 * A note on refcnting: this function will not return, and your proc reference
 * will end up stored in current.  This will make no changes to p's refcnt, so
 * do your accounting such that there is only the +1 for current.  This means if
 * it is already in current (like in the trap return path), don't up it.  If
 * it's already in current and you have another reference (like pid2proc or from
 * an IPI), then down it (which is what happens in __startcore()).  If it's not
 * in current and you have one reference, like proc_run(non_current_p), then
 * also do nothing.  The refcnt for your *p will count for the reference stored
 * in current. */
static void __proc_startcore(struct proc *p, trapframe_t *tf)
{
        assert(!irq_is_enabled());
        __set_proc_current(p);
        /* need to load our silly state, preferably somewhere other than here so we
         * can avoid the case where the context was just running here.  it's not
         * sufficient to do it in the "new process" if-block above (could be things
         * like page faults that cause us to keep the same process, but want a
         * different context.
         * for now, we load this silly state here. (TODO) (HSS)
         * We also need this to be per trapframe, and not per process...
         * For now / OSDI, only load it when in _S mode.  _M mode was handled in
         * __startcore.  */
        if (p->state == PROC_RUNNING_S)
                env_pop_ancillary_state(p);
        /* Clear the current_tf, since it is no longer used */
        current_tf = 0;
        env_pop_tf(tf);
}

/* Restarts/runs the current_tf, which must be for the current process, on the
 * core this code executes on.  Calls an internal function to do the work.
 *
 * In case there are pending routine messages, like __death, __preempt, or
 * __notify, we need to run them.  Alternatively, if there are any, we could
 * self_ipi, and run the messages immediately after popping back to userspace,
 * but that would have crappy overhead.
 *
 * Refcnting: this will not return, and it assumes that you've accounted for
 * your reference as if it was the ref for "current" (which is what happens when
 * returning from local traps and such. */
void proc_restartcore(void)
{
        struct per_cpu_info *pcpui = &per_cpu_info[core_id()];
        assert(!pcpui->cur_sysc);
        /* If there is no cur_tf, it is because the old one was already restarted
         * (and we weren't interrupting another one to finish).  In which case, we
         * should just smp_idle() */
        if (!pcpui->cur_tf) {
                /* It is possible for us to have current loaded if a kthread restarted
                 * after the process yielded the core. */
                abandon_core();
                smp_idle();
        }
        /* Need ints disabled when we return from processing (race) */
        disable_irq();
        /* Need to be current (set by the caller), in case a kmsg is there that
         * tries to clobber us. */
        process_routine_kmsg(pcpui->cur_tf);
        __proc_startcore(pcpui->cur_proc, pcpui->cur_tf);
}

/*
 * Destroys the given process.  This may be called from another process, a light
 * kernel thread (no real process context), asynchronously/cross-core, or from
 * the process on its own core.
 *
 * Here's the way process death works:
 * 0. grab the lock (protects state transition and core map)
 * 1. set state to dying.  that keeps the kernel from doing anything for the
 * process (like proc_running it).
 * 2. figure out where the process is running (cross-core/async or RUNNING_M)
 * 3. IPI to clean up those cores (decref, etc).
 * 4. Unlock
 * 5. Clean up your core, if applicable
 * (Last core/kernel thread to decref cleans up and deallocates resources.)
 *
 * Note that some cores can be processing async calls, but will eventually
 * decref.  Should think about this more, like some sort of callback/revocation.
 *
 * This will eat your reference if it won't return.  Note that this function
 * needs to change anyways when we make __death more like __preempt.  (TODO) */
void proc_destroy(struct proc *p)
{
        bool self_ipi_pending = FALSE;
        
        spin_lock(&p->proc_lock);
        /* TODO: (DEATH) look at this again when we sort the __death IPI */
        if (current == p)
                self_ipi_pending = TRUE;

        switch (p->state) {
                case PROC_DYING: // someone else killed this already.
                        spin_unlock(&p->proc_lock);
                        __proc_kmsg_pending(p, self_ipi_pending);
                        return;
                case PROC_RUNNABLE_M:
                        /* Need to reclaim any cores this proc might have, even though it's
                         * not running yet. */
                        __proc_take_allcores(p, 0, 0, 0, 0);
                        // fallthrough
                case PROC_RUNNABLE_S:
                        // Think about other lists, like WAITING, or better ways to do this
                        deschedule_proc(p);
                        break;
                case PROC_RUNNING_S:
                        #if 0
                        // here's how to do it manually
                        if (current == p) {
                                lcr3(boot_cr3);
                                proc_decref(p);         /* this decref is for the cr3 */
                                current = NULL;
                        }
                        #endif
                        send_kernel_message(get_pcoreid(p, 0), __death, 0, 0, 0,
                                            KMSG_ROUTINE);
                        __seq_start_write(&p->procinfo->coremap_seqctr);
                        // TODO: might need to sort num_vcores too later (VC#)
                        /* vcore is unmapped on the receive side */
                        __seq_end_write(&p->procinfo->coremap_seqctr);
                        #if 0
                        /* right now, RUNNING_S only runs on a mgmt core (0), not cores
                         * managed by the idlecoremap.  so don't do this yet. */
                        put_idle_core(get_pcoreid(p, 0));
                        #endif
                        break;
                case PROC_RUNNING_M:
                        /* Send the DEATH message to every core running this process, and
                         * deallocate the cores.
                         * The rule is that the vcoremap is set before proc_run, and reset
                         * within proc_destroy */
                        __proc_take_allcores(p, __death, 0, 0, 0);
                        break;
                case PROC_CREATED:
                        break;
                default:
                        panic("Weird state(%s) in %s()", procstate2str(p->state),
                              __FUNCTION__);
        }
        __proc_set_state(p, PROC_DYING);
        /* This prevents processes from accessing their old files while dying, and
         * will help if these files (or similar objects in the future) hold
         * references to p (preventing a __proc_free()). */
        close_all_files(&p->open_files, FALSE);
        /* This decref is for the process's existence. */
        proc_decref(p);
        /* Unlock and possible decref and wait.  A death IPI should be on its way,
         * either from the RUNNING_S one, or from proc_take_cores with a __death.
         * in general, interrupts should be on when you call proc_destroy locally,
         * but currently aren't for all things (like traphandlers). */
        spin_unlock(&p->proc_lock);
        /* at this point, we normally have one ref to be eaten in kmsg_pending and
         * one for every 'current'.  and maybe one for a parent */
        __proc_kmsg_pending(p, self_ipi_pending);
        return;
}

/* Helper function.  Is the given pcore a mapped vcore?  No locking involved, be
 * careful. */
static bool is_mapped_vcore(struct proc *p, uint32_t pcoreid)
{
        return p->procinfo->pcoremap[pcoreid].valid;
}

/* Helper function.  Find the vcoreid for a given physical core id for proc p.
 * No locking involved, be careful.  Panics on failure. */
static uint32_t get_vcoreid(struct proc *p, uint32_t pcoreid)
{
        assert(is_mapped_vcore(p, pcoreid));
        return p->procinfo->pcoremap[pcoreid].vcoreid;
}

/* Helper function.  Find the pcoreid for a given virtual core id for proc p.
 * No locking involved, be careful.  Panics on failure. */
static uint32_t get_pcoreid(struct proc *p, uint32_t vcoreid)
{
        assert(vcore_is_mapped(p, vcoreid));
        return p->procinfo->vcoremap[vcoreid].pcoreid;
}

/* Helper function: yields / wraps up current_tf and schedules the _S */
void __proc_yield_s(struct proc *p, struct trapframe *tf)
{
        assert(p->state == PROC_RUNNING_S);
        p->env_tf= *tf;
        env_push_ancillary_state(p);                    /* TODO: (HSS) */
        __proc_set_state(p, PROC_RUNNABLE_S);
        schedule_proc(p);
}

/* Yields the calling core.  Must be called locally (not async) for now.
 * - If RUNNING_S, you just give up your time slice and will eventually return.
 * - If RUNNING_M, you give up the current vcore (which never returns), and
 *   adjust the amount of cores wanted/granted.
 * - If you have only one vcore, you switch to RUNNABLE_M.  When you run again,
 *   you'll have one guaranteed core, starting from the entry point.
 *
 * - RES_CORES amt_wanted will be the amount running after taking away the
 *   yielder, unless there are none left, in which case it will be 1.
 *
 * If the call is being nice, it means that it is in response to a preemption
 * (which needs to be checked).  If there is no preemption pending, just return.
 * No matter what, don't adjust the number of cores wanted.
 *
 * This usually does not return (abandon_core()), so it will eat your reference.
 * */
void proc_yield(struct proc *SAFE p, bool being_nice)
{
        uint32_t vcoreid = get_vcoreid(p, core_id());
        struct vcore *vc = vcoreid2vcore(p, vcoreid);
        struct preempt_data *vcpd = &p->procdata->vcore_preempt_data[vcoreid];

        /* no reason to be nice, return */
        if (being_nice && !vc->preempt_pending)
                return;

        spin_lock(&p->proc_lock); /* horrible scalability.  =( */

        /* fate is sealed, return and take the preempt message on the way out.
         * we're making this check while holding the lock, since the preemptor
         * should hold the lock when sending messages. */
        if (vc->preempt_served) {
                spin_unlock(&p->proc_lock);
                return;
        }
        /* no need to preempt later, since we are yielding (nice or otherwise) */
        if (vc->preempt_pending)
                vc->preempt_pending = 0;
        /* Don't let them yield if they are missing a notification.  Userspace must
         * not leave vcore context without dealing with notif_pending.  pop_ros_tf()
         * handles leaving via uthread context.  This handles leaving via a yield.
         *
         * This early check is an optimization.  The real check is below when it
         * works with the online_vcs list (syncing with event.c and INDIR/IPI
         * posting). */
        if (vcpd->notif_pending) {
                spin_unlock(&p->proc_lock);
                return;
        }
        switch (p->state) {
                case (PROC_RUNNING_S):
                        __proc_yield_s(p, current_tf);  /* current_tf 0'd in abandon core */
                        break;
                case (PROC_RUNNING_M):
                        printd("[K] Process %d (%p) is yielding on vcore %d\n", p->pid, p,
                               get_vcoreid(p, core_id()));
                        /* Remove from the online list, add to the yielded list, and unmap
                         * the vcore, which gives up the core. */
                        TAILQ_REMOVE(&p->online_vcs, vc, list);
                        /* Now that we're off the online list, check to see if an alert made
                         * it through (event.c sets this) */
                        cmb();
                        if (vcpd->notif_pending) {
                                /* We lost, put it back on the list and abort the yield */
                                TAILQ_INSERT_TAIL(&p->online_vcs, vc, list); /* could go HEAD */
                                spin_unlock(&p->proc_lock);
                                return;
                        }
                        /* We won the race with event sending, we can safely yield */
                        TAILQ_INSERT_HEAD(&p->inactive_vcs, vc, list);
                        /* Note this protects stuff userspace should look at, which doesn't
                         * include the TAILQs. */
                        __seq_start_write(&p->procinfo->coremap_seqctr);
                        __unmap_vcore(p, vcoreid);
                        /* Adjust implied resource desires */
                        p->resources[RES_CORES].amt_granted = --(p->procinfo->num_vcores);
                        if (!being_nice)
                                p->resources[RES_CORES].amt_wanted = p->procinfo->num_vcores;
                        __seq_end_write(&p->procinfo->coremap_seqctr);
                        // add to idle list
                        put_idle_core(core_id());       /* TODO: prod the ksched? */
                        // last vcore?  then we really want 1, and to yield the gang
                        if (p->procinfo->num_vcores == 0) {
                                p->resources[RES_CORES].amt_wanted = 1;
                                /* wait on an event (not supporting 'being nice' for now */
                                __proc_set_state(p, PROC_WAITING);
                        }
                        break;
                case (PROC_DYING):
                        /* just return and take the death message (which should be otw) */
                        spin_unlock(&p->proc_lock);
                        return;
                default:
                        // there are races that can lead to this (async death, preempt, etc)
                        panic("Weird state(%s) in %s()", procstate2str(p->state),
                              __FUNCTION__);
        }
        spin_unlock(&p->proc_lock);
        proc_decref(p);                 /* need to eat the ref passed in */
        /* TODO: (RMS) If there was a change to the idle cores, try and give our
         * core to someone who was preempted. */
        /* Clean up the core and idle.  For mgmt cores, they will ultimately call
         * manager, which will call schedule() and will repick the yielding proc. */
        abandon_core();
        smp_idle();
}

/* Sends a notification (aka active notification, aka IPI) to p's vcore.  We
 * only send a notification if one isn't already pending and they are enabled.
 * There's a bunch of weird cases with this, and how pending / enabled are
 * signals between the user and kernel - check the documentation.
 *
 * If you expect to notify yourself, cleanup state and process_routine_kmsg() */
void proc_notify(struct proc *p, uint32_t vcoreid)
{
        struct preempt_data *vcpd = &p->procdata->vcore_preempt_data[vcoreid];
        /* TODO: Currently, there is a race for notif_pending, and multiple senders
         * can send an IPI.  Worst thing is that the process gets interrupted
         * briefly and the kernel immediately returns back once it realizes notifs
         * are masked.  To fix it, we'll need atomic_swapb() (right answer), or not
         * use a bool. (wrong answer). */
        if (!vcpd->notif_pending) {
                vcpd->notif_pending = TRUE;
                if (vcpd->notif_enabled) {
                        /* GIANT WARNING: we aren't using the proc-lock to protect the
                         * vcoremap.  We want to be able to use this from interrupt context,
                         * and don't want the proc_lock to be an irqsave.  Spurious
                         * __notify() kmsgs are okay (it checks to see if the right receiver
                         * is current). */
                        if ((p->state & PROC_RUNNING_M) && // TODO: (VC#) (_S state)
                                      vcore_is_mapped(p, vcoreid)) {
                                printd("[kernel] sending notif to vcore %d\n", vcoreid);
                                send_kernel_message(get_pcoreid(p, vcoreid), __notify, (long)p,
                                                    0, 0, KMSG_ROUTINE);
                        }
                }
        }
}

/* Hold the lock before calling this.  If the process is WAITING, it will wake
 * it up and schedule it. */
void __proc_wakeup(struct proc *p)
{
        if (p->state != PROC_WAITING)
                return;
        if (__proc_is_mcp(p))
                __proc_set_state(p, PROC_RUNNABLE_M);
        else
                __proc_set_state(p, PROC_RUNNABLE_S);
        schedule_proc(p);
}

/* Is the process in multi_mode / is an MCP or not?  */
bool __proc_is_mcp(struct proc *p)
{
        /* in lieu of using the amount of cores requested, or having a bunch of
         * states (like PROC_WAITING_M and _S), I'll just track it with a bool. */
        return p->is_mcp;
}

/************************  Preemption Functions  ******************************
 * Don't rely on these much - I'll be sure to change them up a bit.
 *
 * Careful about what takes a vcoreid and what takes a pcoreid.  Also, there may
 * be weird glitches with setting the state to RUNNABLE_M.  It is somewhat in
 * flux.  The num_vcores is changed after take_cores, but some of the messages
 * (or local traps) may not yet be ready to handle seeing their future state.
 * But they should be, so fix those when they pop up.
 *
 * TODO: (RMS) we need to actually make the scheduler handle RUNNABLE_Ms and
 * then schedule these, or change proc_destroy to not assume they need to be
 * descheduled.
 *
 * Another thing to do would be to make the _core functions take a pcorelist,
 * and not just one pcoreid. */

/* Sets a preempt_pending warning for p's vcore, to go off 'when'.  If you care
 * about locking, do it before calling.  Takes a vcoreid! */
void __proc_preempt_warn(struct proc *p, uint32_t vcoreid, uint64_t when)
{
        struct event_msg local_msg = {0};
        /* danger with doing this unlocked: preempt_pending is set, but never 0'd,
         * since it is unmapped and not dealt with (TODO)*/
        p->procinfo->vcoremap[vcoreid].preempt_pending = when;

        /* Send the event (which internally checks to see how they want it) */
        local_msg.ev_type = EV_PREEMPT_PENDING;
        local_msg.ev_arg1 = vcoreid;
        send_kernel_event(p, &local_msg, vcoreid);

        /* TODO: consider putting in some lookup place for the alarm to find it.
         * til then, it'll have to scan the vcoremap (O(n) instead of O(m)) */
}

/* Warns all active vcores of an impending preemption.  Hold the lock if you
 * care about the mapping (and you should). */
void __proc_preempt_warnall(struct proc *p, uint64_t when)
{
        struct vcore *vc_i;
        TAILQ_FOREACH(vc_i, &p->online_vcs, list)
                __proc_preempt_warn(p, vcore2vcoreid(p, vc_i), when);
        /* TODO: consider putting in some lookup place for the alarm to find it.
         * til then, it'll have to scan the vcoremap (O(n) instead of O(m)) */
}

// TODO: function to set an alarm, if none is outstanding

/* Raw function to preempt a single core.  Returns TRUE if the calling core will
 * get a kmsg.  If you care about locking, do it before calling. */
bool __proc_preempt_core(struct proc *p, uint32_t pcoreid)
{
        uint32_t vcoreid = get_vcoreid(p, pcoreid);

        p->procinfo->vcoremap[vcoreid].preempt_served = TRUE;
        // expects a pcorelist.  assumes pcore is mapped and running_m
        return __proc_take_cores(p, &pcoreid, 1, __preempt, (long)p, 0, 0);
}

/* Raw function to preempt every vcore.  Returns TRUE if the calling core will
 * get a kmsg.  If you care about locking, do it before calling. */
bool __proc_preempt_all(struct proc *p)
{
        /* instead of doing this, we could just preempt_served all possible vcores,
         * and not just the active ones.  We would need to sort out a way to deal
         * with stale preempt_serveds first.  This might be just as fast anyways. */
        struct vcore *vc_i;
        TAILQ_FOREACH(vc_i, &p->online_vcs, list)
                vc_i->preempt_served = TRUE;
        return __proc_take_allcores(p, __preempt, (long)p, 0, 0);
}

/* Warns and preempts a vcore from p.  No delaying / alarming, or anything.  The
 * warning will be for u usec from now. */
void proc_preempt_core(struct proc *p, uint32_t pcoreid, uint64_t usec)
{
        bool self_ipi_pending = FALSE;
        uint64_t warn_time = read_tsc() + usec2tsc(usec);

        /* DYING could be okay */
        if (p->state != PROC_RUNNING_M) {
                warn("Tried to preempt from a non RUNNING_M proc!");
                return;
        }
        spin_lock(&p->proc_lock);
        if (is_mapped_vcore(p, pcoreid)) {
                __proc_preempt_warn(p, get_vcoreid(p, pcoreid), warn_time);
                self_ipi_pending = __proc_preempt_core(p, pcoreid);
        } else {
                warn("Pcore doesn't belong to the process!!");
        }
        /* TODO: (RMS) do this once a scheduler can handle RUNNABLE_M, and make sure
         * to schedule it */
        #if 0
        if (!p->procinfo->num_vcores) {
                __proc_set_state(p, PROC_RUNNABLE_M);
                schedule_proc(p);
        }
        #endif
        spin_unlock(&p->proc_lock);
        __proc_kmsg_pending(p, self_ipi_pending);
}

/* Warns and preempts all from p.  No delaying / alarming, or anything.  The
 * warning will be for u usec from now. */
void proc_preempt_all(struct proc *p, uint64_t usec)
{
        bool self_ipi_pending = FALSE;
        uint64_t warn_time = read_tsc() + usec2tsc(usec);

        spin_lock(&p->proc_lock);
        /* DYING could be okay */
        if (p->state != PROC_RUNNING_M) {
                warn("Tried to preempt from a non RUNNING_M proc!");
                spin_unlock(&p->proc_lock);
                return;
        }
        __proc_preempt_warnall(p, warn_time);
        self_ipi_pending = __proc_preempt_all(p);
        assert(!p->procinfo->num_vcores);
        /* TODO: (RMS) do this once a scheduler can handle RUNNABLE_M, and make sure
         * to schedule it */
        #if 0
        __proc_set_state(p, PROC_RUNNABLE_M);
        schedule_proc(p);
        #endif
        spin_unlock(&p->proc_lock);
        __proc_kmsg_pending(p, self_ipi_pending);
}

/* Give the specific pcore to proc p.  Lots of assumptions, so don't really use
 * this.  The proc needs to be _M and prepared for it.  the pcore needs to be
 * free, etc. */
void proc_give(struct proc *p, uint32_t pcoreid)
{
        bool self_ipi_pending = FALSE;

        spin_lock(&p->proc_lock);
        // expects a pcorelist, we give it a list of one
        self_ipi_pending = __proc_give_cores(p, &pcoreid, 1);
        spin_unlock(&p->proc_lock);
        __proc_kmsg_pending(p, self_ipi_pending);
}

/* Global version of the helper, for sys_get_vcoreid (might phase that syscall
 * out). */
uint32_t proc_get_vcoreid(struct proc *SAFE p, uint32_t pcoreid)
{
        uint32_t vcoreid;
        // TODO: the code currently doesn't track the vcoreid properly for _S (VC#)
        spin_lock(&p->proc_lock);
        switch (p->state) {
                case PROC_RUNNING_S:
                        spin_unlock(&p->proc_lock);
                        return 0; // TODO: here's the ugly part
                case PROC_RUNNING_M:
                        vcoreid = get_vcoreid(p, pcoreid);
                        spin_unlock(&p->proc_lock);
                        return vcoreid;
                case PROC_DYING: // death message is on the way
                        spin_unlock(&p->proc_lock);
                        return 0;
                default:
                        spin_unlock(&p->proc_lock);
                        panic("Weird state(%s) in %s()", procstate2str(p->state),
                              __FUNCTION__);
        }
}

/* TODO: make all of these static inlines when we gut the env crap */
bool vcore_is_mapped(struct proc *p, uint32_t vcoreid)
{
        return p->procinfo->vcoremap[vcoreid].valid;
}

/* Can do this, or just create a new field and save it in the vcoremap */
uint32_t vcore2vcoreid(struct proc *p, struct vcore *vc)
{
        return (vc - p->procinfo->vcoremap);
}

struct vcore *vcoreid2vcore(struct proc *p, uint32_t vcoreid)
{
        return &p->procinfo->vcoremap[vcoreid];
}

/* Helper: gives pcore to the process, mapping it to the next available vcore */
static void __proc_give_a_pcore(struct proc *p, uint32_t pcore)
{
        struct vcore *new_vc;
        new_vc = TAILQ_FIRST(&p->inactive_vcs);
        /* there are cases where this isn't true; deal with it later */
        assert(new_vc);
        printd("setting vcore %d to pcore %d\n", vcore2vcoreid(p, new_vc),
               pcorelist[i]);
        TAILQ_REMOVE(&p->inactive_vcs, new_vc, list);
        TAILQ_INSERT_TAIL(&p->online_vcs, new_vc, list);
        __map_vcore(p, vcore2vcoreid(p, new_vc), pcore);
}

/* Gives process p the additional num cores listed in pcorelist.  You must be
 * RUNNABLE_M or RUNNING_M before calling this.  If you're RUNNING_M, this will
 * startup your new cores at the entry point with their virtual IDs (or restore
 * a preemption).  If you're RUNNABLE_M, you should call proc_run after this so
 * that the process can start to use its cores.
 *
 * If you're *_S, make sure your core0's TF is set (which is done when coming in
 * via arch/trap.c and we are RUNNING_S), change your state, then call this.
 * Then call proc_run().
 *
 * The reason I didn't bring the _S cases from core_request over here is so we
 * can keep this family of calls dealing with only *_Ms, to avoiding caring if
 * this is called from another core, and to avoid the need_to_idle business.
 * The other way would be to have this function have the side effect of changing
 * state, and finding another way to do the need_to_idle.
 *
 * The returned bool signals whether or not a stack-crushing IPI will come in
 * once you unlock after this function.
 *
 * WARNING: You must hold the proc_lock before calling this! */
bool __proc_give_cores(struct proc *SAFE p, uint32_t *pcorelist, size_t num)
{
        bool self_ipi_pending = FALSE;
        switch (p->state) {
                case (PROC_RUNNABLE_S):
                case (PROC_RUNNING_S):
                        panic("Don't give cores to a process in a *_S state!\n");
                        break;
                case (PROC_DYING):
                        panic("Attempted to give cores to a DYING process.\n");
                        break;
                case (PROC_RUNNABLE_M):
                        // set up vcoremap.  list should be empty, but could be called
                        // multiple times before proc_running (someone changed their mind?)
                        if (p->procinfo->num_vcores) {
                                printk("[kernel] Yaaaaaarrrrr!  Giving extra cores, are we?\n");
                                // debugging: if we aren't packed, then there's a problem
                                // somewhere, like someone forgot to take vcores after
                                // preempting.
                                for (int i = 0; i < p->procinfo->num_vcores; i++)
                                        assert(vcore_is_mapped(p, i));
                        }
                        // add new items to the vcoremap
                        __seq_start_write(&p->procinfo->coremap_seqctr);
                        p->procinfo->num_vcores += num;
                        /* TODO: consider bulk preemption */
                        for (int i = 0; i < num; i++)
                                __proc_give_a_pcore(p, pcorelist[i]);
                        __seq_end_write(&p->procinfo->coremap_seqctr);
                        break;
                case (PROC_RUNNING_M):
                        /* Up the refcnt, since num cores are going to start using this
                         * process and have it loaded in their 'current'. */
                        proc_incref(p, num);
                        __seq_start_write(&p->procinfo->coremap_seqctr);
                        p->procinfo->num_vcores += num;
                        for (int i = 0; i < num; i++) {
                                __proc_give_a_pcore(p, pcorelist[i]);
                                send_kernel_message(pcorelist[i], __startcore, (long)p, 0, 0,
                                                    KMSG_ROUTINE);
                                if (pcorelist[i] == core_id())
                                        self_ipi_pending = TRUE;
                        }
                        __seq_end_write(&p->procinfo->coremap_seqctr);
                        break;
                default:
                        panic("Weird state(%s) in %s()", procstate2str(p->state),
                              __FUNCTION__);
        }
        p->resources[RES_CORES].amt_granted += num;
        return self_ipi_pending;
}

/* Makes process p's coremap look like pcorelist (add, remove, etc).  Caller
 * needs to know what cores are free after this call (removed, failed, etc).
 * This info will be returned via corelist and *num.  This will send message to
 * any cores that are getting removed.
 *
 * Before implementing this, we should probably think about when this will be
 * used.  Implies preempting for the message.  The more that I think about this,
 * the less I like it.  For now, don't use this, and think hard before
 * implementing it.
 *
 * WARNING: You must hold the proc_lock before calling this! */
bool __proc_set_allcores(struct proc *SAFE p, uint32_t *pcorelist,
                         size_t *num, amr_t message,TV(a0t) arg0,
                         TV(a1t) arg1, TV(a2t) arg2)
{
        panic("Set all cores not implemented.\n");
}

/* Helper for the take_cores calls: takes a specific vcore from p, optionally
 * sending the message (or just unmapping), gives the pcore to the idlecoremap,
 * and returns TRUE if a self_ipi is pending. */
static bool __proc_take_a_core(struct proc *p, struct vcore *vc, amr_t message,
                               long arg0, long arg1, long arg2)
{
        bool self_ipi_pending = FALSE;
        /* Change lists for the vcore.  We do this before either unmapping or
         * sending the message, so the lists represent what will be very soon
         * (before we unlock, the messages are in flight). */
        TAILQ_REMOVE(&p->online_vcs, vc, list);
        TAILQ_INSERT_HEAD(&p->inactive_vcs, vc, list);
        if (message) {
                if (vc->pcoreid == core_id())
                        self_ipi_pending = TRUE;
                send_kernel_message(vc->pcoreid, message, arg0, arg1, arg2,
                                    KMSG_ROUTINE);
        } else {
                /* if there was a msg, the vcore is unmapped on the receive side.
                 * o/w, we need to do it here. */
                __unmap_vcore(p, vcore2vcoreid(p, vc));
        }
        /* give the pcore back to the idlecoremap */
        put_idle_core(vc->pcoreid);
        return self_ipi_pending;
}

/* Takes from process p the num cores listed in pcorelist, using the given
 * message for the kernel message (__death, __preempt, etc).  Like the others
 * in this function group, bool signals whether or not an IPI is pending.
 *
 * WARNING: You must hold the proc_lock before calling this! */
bool __proc_take_cores(struct proc *p, uint32_t *pcorelist, size_t num,
                       amr_t message, long arg0, long arg1, long arg2)
{
        uint32_t vcoreid;
        bool self_ipi_pending = FALSE;
        switch (p->state) {
                case (PROC_RUNNABLE_M):
                        assert(!message);
                        break;
                case (PROC_RUNNING_M):
                        assert(message);
                        break;
                default:
                        panic("Weird state(%s) in %s()", procstate2str(p->state),
                              __FUNCTION__);
        }
        spin_lock(&idle_lock);
        assert((num <= p->procinfo->num_vcores) &&
               (num_idlecores + num <= num_cpus));
        spin_unlock(&idle_lock);
        __seq_start_write(&p->procinfo->coremap_seqctr);
        for (int i = 0; i < num; i++) {
                vcoreid = get_vcoreid(p, pcorelist[i]);
                /* Sanity check */
                assert(pcorelist[i] == get_pcoreid(p, vcoreid));
                self_ipi_pending = __proc_take_a_core(p, vcoreid2vcore(p, vcoreid),
                                                      message, arg0, arg1, arg2);
        }
        p->procinfo->num_vcores -= num;
        __seq_end_write(&p->procinfo->coremap_seqctr);
        p->resources[RES_CORES].amt_granted -= num;
        return self_ipi_pending;
}

/* Takes all cores from a process, which must be in an _M state.  Cores are
 * placed back in the idlecoremap.  If there's a message, such as __death or
 * __preempt, it will be sent to the cores.  The bool signals whether or not an
 * IPI is coming in once you unlock.
 *
 * WARNING: You must hold the proc_lock before calling this! */
bool __proc_take_allcores(struct proc *p, amr_t message, long arg0, long arg1,
                          long arg2)
{
        struct vcore *vc_i, *vc_temp;
        bool self_ipi_pending = FALSE;
        switch (p->state) {
                case (PROC_RUNNABLE_M):
                        assert(!message);
                        break;
                case (PROC_RUNNING_M):
                        assert(message);
                        break;
                default:
                        panic("Weird state(%s) in %s()", procstate2str(p->state),
                              __FUNCTION__);
        }
        spin_lock(&idle_lock);
        assert(num_idlecores + p->procinfo->num_vcores <= num_cpus); // sanity
        spin_unlock(&idle_lock);
        __seq_start_write(&p->procinfo->coremap_seqctr);
        TAILQ_FOREACH_SAFE(vc_i, &p->online_vcs, list, vc_temp) {
                self_ipi_pending = __proc_take_a_core(p, vc_i,
                                                      message, arg0, arg1, arg2);
        }
        p->procinfo->num_vcores = 0;
        assert(TAILQ_EMPTY(&p->online_vcs));
        __seq_end_write(&p->procinfo->coremap_seqctr);
        p->resources[RES_CORES].amt_granted = 0;
        return self_ipi_pending;
}

/* Helper, to be used when a proc management kmsg should be on its way.  This
 * used to also unlock and then handle the message, back when the proc_lock was
 * an irqsave, and we had an IPI pending.  Now we use routine kmsgs.  If a msg
 * is pending, this needs to decref (to eat the reference of the caller) and
 * then process the message.  Unlock before calling this, since you might not
 * return.
 *
 * There should already be a kmsg waiting for us, since when we checked state to
 * see a message was coming, the message had already been sent before unlocking.
 * Note we do not need interrupts enabled for this to work (you can receive a
 * message before its IPI by polling), though in most cases they will be.
 *
 * TODO: consider inlining this, so __FUNCTION__ works (will require effort in
 * core_request(). */
void __proc_kmsg_pending(struct proc *p, bool ipi_pending)
{
        if (ipi_pending) {
                proc_decref(p);
                process_routine_kmsg(0);
                panic("stack-killing kmsg not found in %s!!!", __FUNCTION__);
        }
}

/* Helper to do the vcore->pcore and inverse mapping.  Hold the lock when
 * calling. */
void __map_vcore(struct proc *p, uint32_t vcoreid, uint32_t pcoreid)
{
        p->procinfo->vcoremap[vcoreid].pcoreid = pcoreid;
        p->procinfo->vcoremap[vcoreid].valid = TRUE;
        p->procinfo->pcoremap[pcoreid].vcoreid = vcoreid;
        p->procinfo->pcoremap[pcoreid].valid = TRUE;
}

/* Helper to unmap the vcore->pcore and inverse mapping.  Hold the lock when
 * calling. */
void __unmap_vcore(struct proc *p, uint32_t vcoreid)
{
        p->procinfo->vcoremap[vcoreid].valid = FALSE;
        p->procinfo->pcoremap[p->procinfo->vcoremap[vcoreid].pcoreid].valid = FALSE;
}

/* Stop running whatever context is on this core, load a known-good cr3, and
 * 'idle'.  Note this leaves no trace of what was running. This "leaves the
 * process's context. */
void abandon_core(void)
{
        struct per_cpu_info *pcpui = &per_cpu_info[core_id()];
        /* Syscalls that don't return will ultimately call abadon_core(), so we need
         * to make sure we don't think we are still working on a syscall. */
        pcpui->cur_sysc = 0;
        if (pcpui->cur_proc) {
                pcpui->cur_tf = 0;
                __abandon_core();
        }
}

/* Switches to the address space/context of new_p, doing nothing if we are
 * already in new_p.  This won't add extra refcnts or anything, and needs to be
 * paired with switch_back() at the end of whatever function you are in.  Don't
 * migrate cores in the middle of a pair.  Specifically, the uncounted refs are
 * one for the old_proc, which is passed back to the caller, and new_p is
 * getting placed in cur_proc. */
struct proc *switch_to(struct proc *new_p)
{
        struct per_cpu_info *pcpui = &per_cpu_info[core_id()];
        struct proc *old_proc = pcpui->cur_proc;        /* uncounted ref */
        /* If we aren't the proc already, then switch to it */
        if (old_proc != new_p) {
                pcpui->cur_proc = new_p;                                /* uncounted ref */
                lcr3(new_p->env_cr3);
        }
        return old_proc;
}

/* This switches back to old_proc from new_p.  Pair it with switch_to(), and
 * pass in its return value for old_proc. */
void switch_back(struct proc *new_p, struct proc *old_proc)
{
        struct per_cpu_info *pcpui = &per_cpu_info[core_id()];
        if (old_proc != new_p) {
                pcpui->cur_proc = old_proc;
                if (old_proc)
                        lcr3(old_proc->env_cr3);
                else
                        lcr3(boot_cr3);
        }
}

/* Will send a TLB shootdown message to every vcore in the main address space
 * (aka, all vcores for now).  The message will take the start and end virtual
 * addresses as well, in case we want to be more clever about how much we
 * shootdown and batching our messages.  Should do the sanity about rounding up
 * and down in this function too.
 *
 * Would be nice to have a broadcast kmsg at this point.  Note this may send a
 * message to the calling core (interrupting it, possibly while holding the
 * proc_lock).  We don't need to process routine messages since it's an
 * immediate message. */
void proc_tlbshootdown(struct proc *p, uintptr_t start, uintptr_t end)
{
        struct vcore *vc_i;
        /* TODO: we might be able to avoid locking here in the future (we must hit
         * all online, and we can check __mapped).  it'll be complicated. */
        spin_lock(&p->proc_lock);
        switch (p->state) {
                case (PROC_RUNNING_S):
                        tlbflush();
                        break;
                case (PROC_RUNNING_M):
                        /* TODO: (TLB) sanity checks and rounding on the ranges */
                        TAILQ_FOREACH(vc_i, &p->online_vcs, list) {
                                send_kernel_message(vc_i->pcoreid, __tlbshootdown, start, end,
                                                    0, KMSG_IMMEDIATE);
                        }
                        break;
                case (PROC_DYING):
                        /* if it is dying, death messages are already on the way to all
                         * cores, including ours, which will clear the TLB. */
                        break;
                default:
                        /* will probably get this when we have the short handlers */
                        warn("Unexpected case %s in %s", procstate2str(p->state),
                             __FUNCTION__);
        }
        spin_unlock(&p->proc_lock);
}

/* Kernel message handler to start a process's context on this core.  Tightly
 * coupled with proc_run().  Interrupts are disabled. */
void __startcore(struct trapframe *tf, uint32_t srcid, long a0, long a1, long a2)
{
        uint32_t pcoreid = core_id(), vcoreid;
        struct proc *p_to_run = (struct proc *CT(1))a0;
        struct trapframe local_tf;
        struct preempt_data *vcpd;

        assert(p_to_run);
        /* the sender of the amsg increfed, thinking we weren't running current. */
        if (p_to_run == current)
                proc_decref(p_to_run);
        vcoreid = get_vcoreid(p_to_run, pcoreid);
        vcpd = &p_to_run->procdata->vcore_preempt_data[vcoreid];
        /* We could let userspace do this, though they come into vcore entry many
         * times, and we just need this to happen when the cores comes online the
         * first time.  That, and they want this turned on as soon as we know a
         * vcore *WILL* be online.  We could also do this earlier, when we map the
         * vcore to its pcore, though we don't always have current loaded or
         * otherwise mess with the VCPD in those code paths. */
        vcpd->can_rcv_msg = TRUE;
        printd("[kernel] startcore on physical core %d for process %d's vcore %d\n",
               pcoreid, p_to_run->pid, vcoreid);
        if (seq_is_locked(vcpd->preempt_tf_valid)) {
                __seq_end_write(&vcpd->preempt_tf_valid); /* mark tf as invalid */
                restore_fp_state(&vcpd->preempt_anc);
                /* notif_pending and enabled means the proc wants to receive the IPI,
                 * but might have missed it.  copy over the tf so they can restart it
                 * later, and give them a fresh vcore. */
                if (vcpd->notif_pending && vcpd->notif_enabled) {
                        vcpd->notif_tf = vcpd->preempt_tf; // could memset
                        proc_init_trapframe(&local_tf, vcoreid, p_to_run->env_entry,
                                            vcpd->transition_stack);
                        if (!vcpd->transition_stack)
                                warn("No transition stack!");
                        vcpd->notif_enabled = FALSE;
                        vcpd->notif_pending = FALSE;
                } else {
                        /* copy-in the tf we'll pop, then set all security-related fields */
                        local_tf = vcpd->preempt_tf;
                        proc_secure_trapframe(&local_tf);
                }
        } else { /* not restarting from a preemption, use a fresh vcore */
                assert(vcpd->transition_stack);
                proc_init_trapframe(&local_tf, vcoreid, p_to_run->env_entry,
                                    vcpd->transition_stack);
                /* Disable/mask active notifications for fresh vcores */
                vcpd->notif_enabled = FALSE;
        }
        __proc_startcore(p_to_run, &local_tf); // TODO: (HSS) pass silly state *?
}

/* Bail out if it's the wrong process, or if they no longer want a notif.  Make
 * sure that you are passing in a user tf (otherwise, it's a bug).  Try not to
 * grab locks or write access to anything that isn't per-core in here. */
void __notify(struct trapframe *tf, uint32_t srcid, long a0, long a1, long a2)
{
        struct user_trapframe local_tf;
        struct preempt_data *vcpd;
        uint32_t vcoreid;
        struct proc *p = (struct proc*)a0;

        if (p != current)
                return;
        assert(!in_kernel(tf));
        /* We shouldn't need to lock here, since unmapping happens on the pcore and
         * mapping would only happen if the vcore was free, which it isn't until
         * after we unmap. */
        assert(tf == current_tf);
        vcoreid = get_vcoreid(p, core_id());
        vcpd = &p->procdata->vcore_preempt_data[vcoreid];
        printd("received active notification for proc %d's vcore %d on pcore %d\n",
               p->procinfo->pid, vcoreid, core_id());
        /* sort signals.  notifs are now masked, like an interrupt gate */
        if (!vcpd->notif_enabled)
                return;
        vcpd->notif_enabled = FALSE;
        vcpd->notif_pending = FALSE; // no longer pending - it made it here
        /* save the old tf in the notify slot, build and pop a new one.  Note that
         * silly state isn't our business for a notification. */
        // TODO: this is assuming the struct user_tf is the same as a regular TF
        vcpd->notif_tf = *tf;
        memset(&local_tf, 0, sizeof(local_tf));
        proc_init_trapframe(&local_tf, vcoreid, p->env_entry,
                            vcpd->transition_stack);
        __proc_startcore(p, &local_tf);
}

void __preempt(struct trapframe *tf, uint32_t srcid, long a0, long a1, long a2)
{
        struct preempt_data *vcpd;
        uint32_t vcoreid, coreid = core_id();
        struct proc *p = (struct proc*)a0;

        if (p != current)
                panic("__preempt arrived for a process (%p) that was not current (%p)!",
                      p, current);
        assert(!in_kernel(tf));
        /* We shouldn't need to lock here, since unmapping happens on the pcore and
         * mapping would only happen if the vcore was free, which it isn't until
         * after we unmap. */
        vcoreid = get_vcoreid(p, coreid);
        p->procinfo->vcoremap[vcoreid].preempt_served = FALSE;
        /* either __preempt or proc_yield() ends the preempt phase. */
        p->procinfo->vcoremap[vcoreid].preempt_pending = 0;
        vcpd = &p->procdata->vcore_preempt_data[vcoreid];
        printd("[kernel] received __preempt for proc %d's vcore %d on pcore %d\n",
               p->procinfo->pid, vcoreid, core_id());

        /* save the old tf in the preempt slot, save the silly state, and signal the
         * state is a valid tf.  when it is 'written,' it is valid.  Using the
         * seq_ctrs so userspace can tell between different valid versions.  If the
         * TF was already valid, it will panic (if CONFIGed that way). */
        // TODO: this is assuming the struct user_tf is the same as a regular TF
        vcpd->preempt_tf = *tf;
        save_fp_state(&vcpd->preempt_anc);
        __seq_start_write(&vcpd->preempt_tf_valid);
        __unmap_vcore(p, vcoreid);
        abandon_core();
        smp_idle();
}

/* Kernel message handler to clean up the core when a process is dying.
 * Note this leaves no trace of what was running.
 * It's okay if death comes to a core that's already idling and has no current.
 * It could happen if a process decref'd before __proc_startcore could incref. */
void __death(struct trapframe *tf, uint32_t srcid, long a0, long a1, long a2)
{
        uint32_t vcoreid, coreid = core_id();
        if (current) {
                vcoreid = get_vcoreid(current, coreid);
                printd("[kernel] death on physical core %d for process %d's vcore %d\n",
                       coreid, current->pid, vcoreid);
                __unmap_vcore(current, vcoreid);
        }
        abandon_core();
        smp_idle();
}

/* Kernel message handler, usually sent IMMEDIATE, to shoot down virtual
 * addresses from a0 to a1. */
void __tlbshootdown(struct trapframe *tf, uint32_t srcid, long a0, long a1,
                    long a2)
{
        /* TODO: (TLB) something more intelligent with the range */
        tlbflush();
}

void print_idlecoremap(void)
{
        spin_lock(&idle_lock);
        printk("There are %d idle cores.\n", num_idlecores);
        for (int i = 0; i < num_idlecores; i++)
                printk("idlecoremap[%d] = %d\n", i, idlecoremap[i]);
        spin_unlock(&idle_lock);
}

void print_allpids(void)
{
        void print_proc_state(void *item)
        {
                struct proc *p = (struct proc*)item;
                assert(p);
                printk("%8d %s\n", p->pid, procstate2str(p->state));
        }
        printk("PID      STATE    \n");
        printk("------------------\n");
        spin_lock(&pid_hash_lock);
        hash_for_each(pid_hash, print_proc_state);
        spin_unlock(&pid_hash_lock);
}

void print_proc_info(pid_t pid)
{
        int j = 0;
        struct proc *p = pid2proc(pid);
        struct vcore *vc_i;
        if (!p) {
                printk("Bad PID.\n");
                return;
        }
        spinlock_debug(&p->proc_lock);
        //spin_lock(&p->proc_lock); // No locking!!
        printk("struct proc: %p\n", p);
        printk("PID: %d\n", p->pid);
        printk("PPID: %d\n", p->ppid);
        printk("State: 0x%08x (%s)\n", p->state, p->is_mcp ? "M" : "S");
        printk("Refcnt: %d\n", atomic_read(&p->p_kref.refcount) - 1);
        printk("Flags: 0x%08x\n", p->env_flags);
        printk("CR3(phys): 0x%08x\n", p->env_cr3);
        printk("Num Vcores: %d\n", p->procinfo->num_vcores);
        printk("Vcore Lists (may be in flux w/o locking):\n----------------------\n");
        printk("Online:\n");
        TAILQ_FOREACH(vc_i, &p->online_vcs, list)
                printk("\tVcore %d -> Pcore %d\n", vcore2vcoreid(p, vc_i), vc_i->pcoreid);
        printk("Bulk Preempted:\n");
        TAILQ_FOREACH(vc_i, &p->bulk_preempted_vcs, list)
                printk("\tVcore %d\n", vcore2vcoreid(p, vc_i));
        printk("Inactive / Yielded:\n");
        TAILQ_FOREACH(vc_i, &p->inactive_vcs, list)
                printk("\tVcore %d\n", vcore2vcoreid(p, vc_i));
        printk("Resources:\n------------------------\n");
        for (int i = 0; i < MAX_NUM_RESOURCES; i++)
                printk("\tRes type: %02d, amt wanted: %08d, amt granted: %08d\n", i,
                       p->resources[i].amt_wanted, p->resources[i].amt_granted);
        printk("Open Files:\n");
        struct files_struct *files = &p->open_files;
        spin_lock(&files->lock);
        for (int i = 0; i < files->max_files; i++)
                if (files->fd_array[i].fd_file) {
                        printk("\tFD: %02d, File: %08p, File name: %s\n", i,
                               files->fd_array[i].fd_file,
                               file_name(files->fd_array[i].fd_file));
                }
        spin_unlock(&files->lock);
        /* No one cares, and it clutters the terminal */
        //printk("Vcore 0's Last Trapframe:\n");
        //print_trapframe(&p->env_tf);
        /* no locking / unlocking or refcnting */
        // spin_unlock(&p->proc_lock);
        proc_decref(p);
}