-/* Copyright (c) 2010 The Regents of the University of California
+/* Copyright (c) 2010-13 The Regents of the University of California
* Barret Rhoden <brho@cs.berkeley.edu>
* See LICENSE for details.
*
#include <pmap.h>
#include <smp.h>
#include <schedule.h>
+#include <kstack.h>
+#include <kmalloc.h>
+#include <arch/uaccess.h>
+
+#define KSTACK_NR_GUARD_PGS 1
+#define KSTACK_GUARD_SZ (KSTACK_NR_GUARD_PGS * PGSIZE)
+static struct kmem_cache *kstack_cache;
+
+/* We allocate KSTKSIZE + PGSIZE vaddrs. So for one-page stacks, we get two
+ * pages. blob points to the bottom of this space. Our job is to allocate the
+ * physical pages for the stack and set up the virtual-to-physical mappings. */
+int kstack_ctor(void *blob, void *priv, int flags)
+{
+ void *stackbot;
+
+ stackbot = kpages_alloc(KSTKSIZE, flags);
+ if (!stackbot)
+ return -1;
+ if (map_vmap_segment((uintptr_t)blob, 0x123456000, KSTACK_NR_GUARD_PGS,
+ PTE_NONE))
+ goto error;
+ if (map_vmap_segment((uintptr_t)blob + KSTACK_GUARD_SZ, PADDR(stackbot),
+ KSTKSIZE / PGSIZE, PTE_KERN_RW))
+ goto error;
+ return 0;
+error:
+ /* On failure, we only need to undo what our dtor would do. The unmaps
+ * happen in the vmap_arena ffunc. */
+ kpages_free(stackbot, KSTKSIZE);
+ return -1;
+}
+
+/* The vmap_arena free will unmap the vaddrs on its own. We just need to free
+ * the physical memory we allocated in ctor. Although we still have mappings
+ * and TLB entries pointing to the memory after we free it (and thus it can be
+ * reused), this is no more dangerous than just freeing the stack. Errant
+ * pointers into an old kstack are still dangerous. */
+void kstack_dtor(void *blob, void *priv)
+{
+ void *stackbot;
+ pte_t pte;
+
+ pte = pgdir_walk(boot_pgdir, blob + KSTACK_GUARD_SZ, 0);
+ assert(pte_walk_okay(pte));
+ stackbot = KADDR(pte_get_paddr(pte));
+ kpages_free(stackbot, KSTKSIZE);
+}
+
+uintptr_t get_kstack(void)
+{
+ void *blob;
+
+ blob = kmem_cache_alloc(kstack_cache, MEM_ATOMIC);
+ /* TODO: think about MEM_WAIT within kthread/blocking code. */
+ assert(blob);
+ return (uintptr_t)blob + KSTKSIZE + KSTACK_GUARD_SZ;
+}
+
+void put_kstack(uintptr_t stacktop)
+{
+ kmem_cache_free(kstack_cache, (void*)(stacktop - KSTKSIZE
+ - KSTACK_GUARD_SZ));
+}
+
+uintptr_t *kstack_bottom_addr(uintptr_t stacktop)
+{
+ /* canary at the bottom of the stack */
+ assert(!PGOFF(stacktop));
+ return (uintptr_t*)(stacktop - KSTKSIZE);
+}
struct kmem_cache *kthread_kcache;
void kthread_init(void)
{
kthread_kcache = kmem_cache_create("kthread", sizeof(struct kthread),
- __alignof__(struct kthread), 0, 0, 0);
+ __alignof__(struct kthread), 0,
+ NULL, 0, 0, NULL);
+ kstack_cache = kmem_cache_create("kstack", KSTKSIZE + KSTACK_GUARD_SZ,
+ PGSIZE, 0, vmap_arena, kstack_ctor,
+ kstack_dtor, NULL);
+}
+
+/* Used by early init routines (smp_boot, etc) */
+struct kthread *__kthread_zalloc(void)
+{
+ struct kthread *kthread;
+ kthread = kmem_cache_alloc(kthread_kcache, 0);
+ assert(kthread);
+ memset(kthread, 0, sizeof(struct kthread));
+ return kthread;
+}
+
+/* Helper during early boot, where we jump from the bootstack to a real kthread
+ * stack, then run f(). Note that we don't have a kthread yet (done in smp.c).
+ *
+ * After this, our callee (f) can free the bootstack, if we care, by adding it
+ * to the base arena (use the KERNBASE addr, not the KERN_LOAD_ADDR). */
+void __use_real_kstack(void (*f)(void *arg))
+{
+ struct per_cpu_info *pcpui = &per_cpu_info[core_id()];
+ uintptr_t new_stacktop;
+
+ new_stacktop = get_kstack();
+ set_stack_top(new_stacktop);
+ __reset_stack_pointer(0, new_stacktop, f);
}
/* Starts kthread on the calling core. This does not return, and will handle
{
struct per_cpu_info *pcpui = &per_cpu_info[core_id()];
uintptr_t current_stacktop;
+ struct kthread *cur_kth;
/* Avoid messy complications. The kthread will enable_irqsave() when it
* comes back up. */
disable_irq();
- /* Free any spare, since we need ours to become the spare (since we can't
- * free our current kthread *before* popping it, nor can we free the current
- * stack until we pop to the kthread's stack). */
+ /* Free any spare, since we need the current to become the spare. Without
+ * the spare, we can't free our current kthread/stack (we could free the
+ * kthread, but not the stack, since we're still on it). And we can't free
+ * anything after popping kthread, since we never return. */
if (pcpui->spare) {
- /* assumes the stack is a page, and that stacktop is somewhere in
- * (pg_bottom, pg_bottom + PGSIZE]. Normally, it ought to be pg_bottom
- * + PGSIZE (on x86). kva2page can take any kva, not just a page
- * aligned addr. */
- page_decref(kva2page((void*)pcpui->spare->stacktop - 1));
+ put_kstack(pcpui->spare->stacktop);
kmem_cache_free(kthread_kcache, pcpui->spare);
}
- current_stacktop = get_stack_top();
+ cur_kth = pcpui->cur_kthread;
+ current_stacktop = cur_kth->stacktop;
+ assert(!cur_kth->sysc); /* catch bugs, prev user should clear */
+ /* Set the spare stuff (current kthread, which includes its stacktop) */
+ pcpui->spare = cur_kth;
/* When a kthread runs, its stack is the default kernel stack */
set_stack_top(kthread->stacktop);
-#ifdef __CONFIG_KTHREAD_POISON__
- /* TODO: KTHR-STACK */
- /* Assert and switch to cur stack not in use, kthr stack in use */
- uintptr_t *cur_stack_poison, *kth_stack_poison;
- cur_stack_poison = (uintptr_t*)ROUNDDOWN(current_stacktop - 1, PGSIZE);
- assert(*cur_stack_poison == 0xdeadbeef);
- *cur_stack_poison = 0;
- kth_stack_poison = (uintptr_t*)ROUNDDOWN(kthread->stacktop - 1, PGSIZE);
- assert(!*kth_stack_poison);
- *kth_stack_poison = 0xdeadbeef;
-#endif /* __CONFIG_KTHREAD_POISON__ */
- /* Set the spare stuff (current kthread, current (not kthread) stacktop) */
- pcpui->spare = kthread;
- kthread->stacktop = current_stacktop;
+ pcpui->cur_kthread = kthread;
/* Only change current if we need to (the kthread was in process context) */
if (kthread->proc) {
- /* Load our page tables before potentially decreffing cur_proc */
- lcr3(kthread->proc->env_cr3);
- /* Might have to clear out an existing current. If they need to be set
- * later (like in restartcore), it'll be done on demand. */
- if (pcpui->cur_proc)
- proc_decref(pcpui->cur_proc);
- /* We also transfer our counted ref from kthread->proc to cur_proc */
- pcpui->cur_proc = kthread->proc;
+ if (kthread->proc == pcpui->cur_proc) {
+ /* We're already loaded, but we do need to drop the extra ref stored
+ * in kthread->proc. */
+ proc_decref(kthread->proc);
+ kthread->proc = 0;
+ } else {
+ /* Load our page tables before potentially decreffing cur_proc.
+ *
+ * We don't need to do an EPT flush here. The EPT is flushed and
+ * managed in sync with the VMCS. We won't run a different VM (and
+ * thus *need* a different EPT) without first removing the old GPC,
+ * which ultimately will result in a flushed EPT (on x86, this
+ * actually happens when we clear_owning_proc()). */
+ lcr3(kthread->proc->env_cr3);
+ /* Might have to clear out an existing current. If they need to be
+ * set later (like in restartcore), it'll be done on demand. */
+ if (pcpui->cur_proc)
+ proc_decref(pcpui->cur_proc);
+ /* Transfer our counted ref from kthread->proc to cur_proc. */
+ pcpui->cur_proc = kthread->proc;
+ kthread->proc = 0;
+ }
}
- /* Tell the core which syscall we are running (if any) */
- assert(!pcpui->cur_sysc); /* catch bugs, prev user should clear */
- pcpui->cur_sysc = kthread->sysc;
/* Finally, restart our thread */
- pop_kernel_ctx(&kthread->context);
+ longjmp(&kthread->context, 1);
}
/* Kmsg handler to launch/run a kthread. This must be a routine message, since
struct kthread *kthread = (struct kthread*)a0;
struct per_cpu_info *pcpui = &per_cpu_info[core_id()];
struct proc *cur_proc = pcpui->cur_proc;
-
+
/* Make sure we are a routine kmsg */
assert(in_early_rkmsg_ctx(pcpui));
if (pcpui->owning_proc && pcpui->owning_proc != kthread->proc) {
* kthread. This means the _M is getting interrupted or otherwise
* delayed. If we want to do something other than run it (like send the
* kmsg to another pcore, or ship the context from here to somewhere
- * else/deschedule it (like for an _S)), do it here. */
+ * else/deschedule it (like for an _S)), do it here.
+ *
+ * If you want to do something here, call out to the ksched, then
+ * abandon_core(). */
cmb(); /* do nothing/placeholder */
- #if 0
- /* example of something to do (wrap up and schedule an _S). Note this
- * might not work perfectly, but is just an example. One thing to be
- * careful of is that spin_lock() can't be called if __launch isn't
- * ROUTINE (which it is right now). */
- if (pcpui->owning_proc->state == PROC_RUNNING_S) {
- spin_lock(&pcpui->owning_proc->proc_lock);
- /* Wrap up / yield the _S proc */
- __proc_set_state(pcpui->owning_proc, PROC_WAITING);
- __proc_save_context_s(pcpui->owning_proc, current_ctx);
- spin_unlock(&pcpui->owning_proc->proc_lock);
- proc_wakeup(p);
- abandon_core();
- /* prob need to clear the owning proc? this is some old shit, so
- * don't just uncomment it. */
- }
- #endif
}
/* o/w, just run the kthread. any trapframes that are supposed to run or
* were interrupted will run whenever the kthread smp_idles() or otherwise
sem_down(sem);
}
+void kthread_usleep(uint64_t usec)
+{
+ ERRSTACK(1);
+ /* TODO: classic ksched issue: where do we want the wake up to happen? */
+ struct timer_chain *tchain = &per_cpu_info[core_id()].tchain;
+ struct rendez rv;
+
+ int ret_zero(void *ignored)
+ {
+ return 0;
+ }
+
+ /* "discard the error" style (we run the conditional code) */
+ if (!waserror()) {
+ rendez_init(&rv);
+ rendez_sleep_timeout(&rv, ret_zero, 0, usec);
+ }
+ poperror();
+}
+
+static void __ktask_wrapper(uint32_t srcid, long a0, long a1, long a2)
+{
+ ERRSTACK(1);
+ void (*fn)(void*) = (void (*)(void*))a0;
+ void *arg = (void*)a1;
+ char *name = (char*)a2;
+ struct per_cpu_info *pcpui = &per_cpu_info[core_id()];
+ assert(is_ktask(pcpui->cur_kthread));
+ pcpui->cur_kthread->name = name;
+ /* There are some rendezs out there that aren't wrapped. Though no one can
+ * abort them. Yet. */
+ if (waserror()) {
+ printk("Ktask %s threw error %s\n", name, current_errstr());
+ goto out;
+ }
+ enable_irq();
+ fn(arg);
+out:
+ disable_irq();
+ pcpui->cur_kthread->name = 0;
+ poperror();
+ /* if we blocked, when we return, PRKM will smp_idle() */
+}
+
+/* Creates a kernel task, running fn(arg), named "name". This is just a routine
+ * kernel message that happens to have a name, and is allowed to block. It
+ * won't be associated with any process. For lack of a better place, we'll just
+ * start it on the calling core. Caller (and/or fn) need to deal with the
+ * storage for *name. */
+void ktask(char *name, void (*fn)(void*), void *arg)
+{
+ send_kernel_message(core_id(), __ktask_wrapper, (long)fn, (long)arg,
+ (long)name, KMSG_ROUTINE);
+}
+
/* Semaphores, using kthreads directly */
-void sem_init(struct semaphore *sem, int signals)
+static void debug_downed_sem(struct semaphore *sem);
+static void debug_upped_sem(struct semaphore *sem);
+static void debug_lock_semlist(void);
+static void debug_unlock_semlist(void);
+
+static void sem_init_common(struct semaphore *sem, int signals)
{
TAILQ_INIT(&sem->waiters);
sem->nr_signals = signals;
+#ifdef CONFIG_SEMAPHORE_DEBUG
+ sem->is_on_list = FALSE;
+#endif
+}
+
+void sem_init(struct semaphore *sem, int signals)
+{
+ sem_init_common(sem, signals);
spinlock_init(&sem->lock);
sem->irq_okay = FALSE;
}
void sem_init_irqsave(struct semaphore *sem, int signals)
{
- TAILQ_INIT(&sem->waiters);
- sem->nr_signals = signals;
+ sem_init_common(sem, signals);
spinlock_init_irqsave(&sem->lock);
sem->irq_okay = TRUE;
}
+bool sem_trydown_bulk(struct semaphore *sem, int nr_signals)
+{
+ bool ret = FALSE;
+
+ /* lockless peek */
+ if (sem->nr_signals - nr_signals < 0)
+ return ret;
+ debug_lock_semlist();
+ spin_lock(&sem->lock);
+ if (sem->nr_signals - nr_signals >= 0) {
+ sem->nr_signals--;
+ ret = TRUE;
+ debug_downed_sem(sem);
+ }
+ spin_unlock(&sem->lock);
+ debug_unlock_semlist();
+ return ret;
+}
+
+bool sem_trydown(struct semaphore *sem)
+{
+ return sem_trydown_bulk(sem, 1);
+}
+
+/* Bottom-half of sem_down. This is called after we jumped to the new stack. */
+static void __attribute__((noreturn)) __unlock_and_idle(void *arg)
+{
+ struct semaphore *sem = (struct semaphore*)arg;
+
+ spin_unlock(&sem->lock);
+ debug_unlock_semlist();
+ smp_idle();
+}
+
/* This downs the semaphore and suspends the current kernel context on its
* waitqueue if there are no pending signals. Note that the case where the
* signal is already there is not optimized. */
void sem_down(struct semaphore *sem)
{
- volatile bool blocking = TRUE; /* signal to short circuit when restarting*/
- struct kthread *kthread;
- struct page *page; /* assumption here that stacks are PGSIZE */
+ struct kthread *kthread, *new_kthread;
register uintptr_t new_stacktop;
struct per_cpu_info *pcpui = &per_cpu_info[core_id()];
+ bool irqs_were_on = irq_is_enabled();
assert(can_block(pcpui));
/* Make sure we aren't holding any locks (only works if SPINLOCK_DEBUG) */
- assert(!pcpui->lock_depth);
+ if (pcpui->lock_depth)
+ panic("Kthread tried to sleep, with lockdepth %d\n", pcpui->lock_depth);
/* Try to down the semaphore. If there is a signal there, we can skip all
* of the sleep prep and just return. */
- spin_lock(&sem->lock); /* no need for irqsave, since we disabled ints */
- if (sem->nr_signals > 0) {
- sem->nr_signals--;
- spin_unlock(&sem->lock);
- goto block_return_path;
+#ifdef CONFIG_SEM_SPINWAIT
+ for (int i = 0; i < CONFIG_SEM_SPINWAIT_NR_LOOPS; i++) {
+ if (sem_trydown(sem))
+ goto block_return_path;
+ cpu_relax();
}
- spin_unlock(&sem->lock);
+#else
+ if (sem_trydown(sem))
+ goto block_return_path;
+#endif
+ assert(pcpui->cur_kthread);
/* We're probably going to sleep, so get ready. We'll check again later. */
- /* Try to get the spare first. If there is one, we'll use it (o/w, we'll
- * get a fresh kthread. Why we need this is more clear when we try to
- * restart kthreads. Having them also ought to cut down on contention.
+ kthread = pcpui->cur_kthread;
+ /* We need to have a spare slot for restart, so we also use it when
+ * sleeping. Right now, we need a new kthread to take over if/when our
+ * current kthread sleeps. Use the spare, and if not, get a new one.
+ *
* Note we do this with interrupts disabled (which protects us from
* concurrent modifications). */
if (pcpui->spare) {
- kthread = pcpui->spare;
- /* we're using the spare, so we use the page the spare held */
- new_stacktop = kthread->stacktop;
+ new_kthread = pcpui->spare;
+ new_stacktop = new_kthread->stacktop;
pcpui->spare = 0;
+ /* The old flags could have KTH_IS_KTASK set. The reason is that the
+ * launching of blocked kthreads also uses PRKM, and that KMSG
+ * (__launch_kthread) doesn't return. Thus the soon-to-be spare
+ * kthread, that is launching another, has flags & KTH_IS_KTASK set. */
+ new_kthread->flags = KTH_DEFAULT_FLAGS;
+ new_kthread->proc = 0;
+ new_kthread->name = 0;
} else {
- kthread = kmem_cache_alloc(kthread_kcache, 0);
- assert(kthread);
- assert(!kpage_alloc(&page)); /* decref'd when the kthread is freed */
-#ifdef __CONFIG_KTHREAD_POISON__
- /* TODO: KTHR-STACK don't poison like this */
- *(uintptr_t*)page2kva(page) = 0;
-#endif /* __CONFIG_KTHREAD_POISON__ */
- new_stacktop = (uintptr_t)page2kva(page) + PGSIZE;
+ new_kthread = __kthread_zalloc();
+ new_kthread->flags = KTH_DEFAULT_FLAGS;
+ new_stacktop = get_kstack();
+ new_kthread->stacktop = new_stacktop;
}
- /* This is the stacktop we are currently on and wish to save */
- kthread->stacktop = get_stack_top();
- /* Set the core's new default stack */
+ /* Set the core's new default stack and kthread */
set_stack_top(new_stacktop);
-#ifdef __CONFIG_KTHREAD_POISON__
- /* Mark the new stack as in-use, and unmark the current kthread */
- /* TODO: KTHR-STACK don't poison like this */
- uintptr_t *new_stack_poison, *kth_stack_poison;
- new_stack_poison = (uintptr_t*)ROUNDDOWN(new_stacktop - 1, PGSIZE);
- assert(!*new_stack_poison);
- *new_stack_poison = 0xdeadbeef;
- kth_stack_poison = (uintptr_t*)ROUNDDOWN(kthread->stacktop - 1, PGSIZE);
- assert(*kth_stack_poison == 0xdeadbeef);
- *kth_stack_poison = 0;
-#endif /* __CONFIG_KTHREAD_POISON__ */
- /* The kthread needs to stay in the process context (if there is one), but
- * we want the core (which could be a vcore) to stay in the context too. In
- * the future, we could check owning_proc. If it isn't set, we could leave
- * the process context and transfer the refcnt to kthread->proc. */
- kthread->proc = current;
- /* kthread tracks the syscall it is working on, which implies errno */
- kthread->sysc = pcpui->cur_sysc;
- pcpui->cur_sysc = 0; /* this core no longer works on sysc */
- if (kthread->proc)
+ pcpui->cur_kthread = new_kthread;
+ /* Kthreads that are ktasks are not related to any process, and do not need
+ * to work in a process's address space. They can operate in any address
+ * space that has the kernel mapped (like boot_pgdir, or any pgdir). Some
+ * ktasks may switch_to, at which point they do care about the address
+ * space and must maintain a reference.
+ *
+ * Normal kthreads need to stay in the process context, but we want the core
+ * (which could be a vcore) to stay in the context too. */
+ if (kthread->flags & KTH_SAVE_ADDR_SPACE) {
+ kthread->proc = current;
+ assert(kthread->proc);
+ /* In the future, we could check owning_proc. If it isn't set, we could
+ * clear current and transfer the refcnt to kthread->proc. If so, we'll
+ * need to reset the cr3 to something (boot_cr3 or owning_proc's cr3),
+ * which might not be worth the potentially excessive TLB flush. */
proc_incref(kthread->proc, 1);
- /* Save the context, toggle blocking for the reactivation */
- save_kernel_ctx(&kthread->context);
- if (!blocking)
+ } else {
+ assert(kthread->proc == 0);
+ }
+ if (setjmp(&kthread->context))
goto block_return_path;
- blocking = FALSE; /* for when it starts back up */
- /* Down the semaphore. We need this to be inline. If we're sleeping, once
- * we unlock the kthread could be started up again and can return and start
- * trashing this function's stack, hence the weird control flow. */
+ debug_lock_semlist();
spin_lock(&sem->lock);
- if (sem->nr_signals-- <= 0) {
+ sem->nr_signals -= 1;
+ if (sem->nr_signals < 0) {
TAILQ_INSERT_TAIL(&sem->waiters, kthread, link);
- /* At this point, we know we'll sleep and change stacks later. Once we
- * unlock, we could have the kthread restarted (possibly on another
- * core), so we need to disable irqs until we are on our new stack.
- * Otherwise, if we take an IRQ, we'll be using our stack while another
- * core is using it (restarted kthread). Basically, disabling irqs
- * allows us to atomically unlock and 'yield'. */
- disable_irq();
- } else { /* we didn't sleep */
- goto unwind_sleep_prep;
+ debug_downed_sem(sem); /* need to debug after inserting */
+ /* At this point, we know we'll sleep and change stacks. Once we unlock
+ * the sem, we could have the kthread restarted (possibly on another
+ * core), so we need to leave the old stack before unlocking. If we
+ * don't and we stay on the stack, then if we take an IRQ or NMI (NMI
+ * that doesn't change stacks, unlike x86_64), we'll be using the stack
+ * at the same time as the kthread. We could just disable IRQs, but
+ * that wouldn't protect us from NMIs that don't change stacks. */
+ __reset_stack_pointer(sem, new_stacktop, __unlock_and_idle);
+ assert(0);
}
- spin_unlock(&sem->lock);
- /* Switch to the core's default stack. After this, don't use local
- * variables. TODO: we shouldn't be using new_stacktop either, can't always
- * trust the register keyword (AFAIK). */
- set_stack_pointer(new_stacktop);
- smp_idle(); /* reenables irqs eventually */
- /* smp_idle never returns */
- assert(0);
-unwind_sleep_prep:
/* We get here if we should not sleep on sem (the signal beat the sleep).
- * Note we are not optimizing for cases where the signal won. */
+ * We debug_downed_sem since we actually downed it - just didn't sleep. */
+ debug_downed_sem(sem);
spin_unlock(&sem->lock);
+ debug_unlock_semlist();
printd("[kernel] Didn't sleep, unwinding...\n");
/* Restore the core's current and default stacktop */
- current = kthread->proc; /* arguably unnecessary */
- if (kthread->proc)
+ if (kthread->flags & KTH_SAVE_ADDR_SPACE) {
proc_decref(kthread->proc);
+ kthread->proc = 0;
+ }
set_stack_top(kthread->stacktop);
+ pcpui->cur_kthread = kthread;
/* Save the allocs as the spare */
assert(!pcpui->spare);
- pcpui->spare = kthread;
- /* save the "freshly alloc'd" stack/page, not the one we came in on */
- kthread->stacktop = new_stacktop;
-#ifdef __CONFIG_KTHREAD_POISON__
- /* TODO: KTHR-STACK don't unpoison like this */
- /* switch back to old stack in use, new one not */
- *new_stack_poison = 0;
- *kth_stack_poison = 0xdeadbeef;
-#endif /* __CONFIG_KTHREAD_POISON__ */
+ pcpui->spare = new_kthread;
block_return_path:
printd("[kernel] Returning from being 'blocked'! at %llu\n", read_tsc());
+ /* restart_kthread and longjmp did not reenable IRQs. We need to make sure
+ * irqs are on if they were on when we started to block. If they were
+ * already on and we short-circuited the block, it's harmless to reenable
+ * them. */
+ if (irqs_were_on)
+ enable_irq();
return;
}
+void sem_down_bulk(struct semaphore *sem, int nr_signals)
+{
+ /* This is far from ideal. Our current sem code expects a 1:1 pairing of
+ * signals to waiters. For instance, if we have 10 waiters of -1 each or 1
+ * waiter of -10, we can't tell from looking at the overall structure. We'd
+ * need to track the desired number of signals per waiter.
+ *
+ * Note that if there are a bunch of signals available, sem_down will
+ * quickly do a try_down and return, so we won't block repeatedly. But if
+ * we do block, we could wake up N times. */
+ for (int i = 0; i < nr_signals; i++)
+ sem_down(sem);
+}
+
/* Ups the semaphore. If it was < 0, we need to wake up someone, which we do.
* Returns TRUE if we woke someone, FALSE o/w (used for debugging in some
* places). If we need more control, we can implement a version of the old
bool sem_up(struct semaphore *sem)
{
struct kthread *kthread = 0;
+
+ debug_lock_semlist();
spin_lock(&sem->lock);
if (sem->nr_signals++ < 0) {
assert(!TAILQ_EMPTY(&sem->waiters));
} else {
assert(TAILQ_EMPTY(&sem->waiters));
}
+ debug_upped_sem(sem);
spin_unlock(&sem->lock);
+ debug_unlock_semlist();
/* Note that once we call kthread_runnable(), we cannot touch the sem again.
* Some sems are on stacks. The caller can touch sem, if it knows about the
* memory/usage of the sem. Likewise, we can't touch the kthread either. */
return FALSE;
}
-void sem_down_irqsave(struct semaphore *sem, int8_t *irq_state)
+bool sem_trydown_bulk_irqsave(struct semaphore *sem, int nr_signals,
+ int8_t *irq_state)
{
+ bool ret;
+
disable_irqsave(irq_state);
- sem_down(sem);
+ ret = sem_trydown_bulk(sem, nr_signals);
enable_irqsave(irq_state);
+ return ret;
+}
+
+bool sem_trydown_irqsave(struct semaphore *sem, int8_t *irq_state)
+{
+ return sem_trydown_bulk_irqsave(sem, 1, irq_state);
+}
+
+void sem_down_bulk_irqsave(struct semaphore *sem, int nr_signals,
+ int8_t *irq_state)
+{
+ disable_irqsave(irq_state);
+ sem_down_bulk(sem, nr_signals);
+ enable_irqsave(irq_state);
+}
+
+void sem_down_irqsave(struct semaphore *sem, int8_t *irq_state)
+{
+ sem_down_bulk_irqsave(sem, 1, irq_state);
}
bool sem_up_irqsave(struct semaphore *sem, int8_t *irq_state)
return retval;
}
+/* Sem debugging */
+
+#ifdef CONFIG_SEMAPHORE_DEBUG
+struct semaphore_tailq sems_with_waiters =
+ TAILQ_HEAD_INITIALIZER(sems_with_waiters);
+/* The lock ordering is sems_with_waiters_lock -> any_sem_lock */
+spinlock_t sems_with_waiters_lock = SPINLOCK_INITIALIZER_IRQSAVE;
+
+static void debug_lock_semlist(void)
+{
+ spin_lock_irqsave(&sems_with_waiters_lock);
+}
+
+static void debug_unlock_semlist(void)
+{
+ spin_unlock_irqsave(&sems_with_waiters_lock);
+}
+
+/* this gets called any time we downed the sem, regardless of whether or not we
+ * waited */
+static void debug_downed_sem(struct semaphore *sem)
+{
+ if (TAILQ_EMPTY(&sem->waiters) || sem->is_on_list)
+ return;
+ TAILQ_INSERT_HEAD(&sems_with_waiters, sem, link);
+ sem->is_on_list = TRUE;
+}
+
+/* Called when a sem is upped. It may or may not have waiters, and it may or
+ * may not be on the list. (we could up several times past 0). */
+static void debug_upped_sem(struct semaphore *sem)
+{
+ if (TAILQ_EMPTY(&sem->waiters) && sem->is_on_list) {
+ TAILQ_REMOVE(&sems_with_waiters, sem, link);
+ sem->is_on_list = FALSE;
+ }
+}
+
+#else
+
+static void debug_lock_semlist(void)
+{
+ /* no debugging */
+}
+
+static void debug_unlock_semlist(void)
+{
+ /* no debugging */
+}
+
+static void debug_downed_sem(struct semaphore *sem)
+{
+ /* no debugging */
+}
+
+static void debug_upped_sem(struct semaphore *sem)
+{
+ /* no debugging */
+}
+
+#endif /* CONFIG_SEMAPHORE_DEBUG */
+
+static bool __sem_has_pid(struct semaphore *sem, pid_t pid)
+{
+ struct kthread *kth_i;
+
+ if (pid == -1)
+ return TRUE;
+ TAILQ_FOREACH(kth_i, &sem->waiters, link) {
+ if (kth_i->proc) {
+ if (kth_i->proc->pid == pid)
+ return TRUE;
+ } else {
+ if (pid == 0)
+ return TRUE;
+ }
+ }
+ return FALSE;
+}
+
+static void print_sem_info(struct semaphore *sem, pid_t pid)
+{
+ struct kthread *kth_i;
+
+ /* Always safe to irqsave */
+ spin_lock_irqsave(&sem->lock);
+ if (!__sem_has_pid(sem, pid)) {
+ spin_unlock_irqsave(&sem->lock);
+ return;
+ }
+ printk("Semaphore %p has %d signals (neg = waiters)\n", sem,
+ sem->nr_signals);
+ TAILQ_FOREACH(kth_i, &sem->waiters, link)
+ printk("\tKthread %p (%s), proc %d, sysc %p, pc/frame %p %p\n",
+ kth_i, kth_i->name, kth_i->proc ? kth_i->proc->pid : 0,
+ kth_i->sysc, jmpbuf_get_pc(&kth_i->context),
+ jmpbuf_get_fp(&kth_i->context));
+ printk("\n");
+ spin_unlock_irqsave(&sem->lock);
+}
+
+void print_all_sem_info(pid_t pid)
+{
+#ifdef CONFIG_SEMAPHORE_DEBUG
+ struct semaphore *sem_i;
+ printk("All sems with waiters:\n");
+ spin_lock_irqsave(&sems_with_waiters_lock);
+ TAILQ_FOREACH(sem_i, &sems_with_waiters, link)
+ print_sem_info(sem_i, pid);
+ spin_unlock_irqsave(&sems_with_waiters_lock);
+#else
+ printk("Failed to print all sems: build with CONFIG_SEMAPHORE_DEBUG\n");
+#endif
+}
+
/* Condition variables, using semaphores and kthreads */
void cv_init(struct cond_var *cv)
{
sem_init(&cv->sem, 0);
- spinlock_init(&cv->lock);
+ cv->lock = &cv->internal_lock;
+ spinlock_init(cv->lock);
cv->nr_waiters = 0;
cv->irq_okay = FALSE;
}
void cv_init_irqsave(struct cond_var *cv)
{
sem_init_irqsave(&cv->sem, 0);
- spinlock_init_irqsave(&cv->lock);
+ cv->lock = &cv->internal_lock;
+ spinlock_init_irqsave(cv->lock);
cv->nr_waiters = 0;
cv->irq_okay = TRUE;
}
+void cv_init_with_lock(struct cond_var *cv, spinlock_t *lock)
+{
+ sem_init(&cv->sem, 0);
+ cv->nr_waiters = 0;
+ cv->lock = lock;
+ cv->irq_okay = FALSE;
+}
+
+void cv_init_irqsave_with_lock(struct cond_var *cv, spinlock_t *lock)
+{
+ sem_init_irqsave(&cv->sem, 0);
+ cv->nr_waiters = 0;
+ cv->lock = lock;
+ cv->irq_okay = TRUE;
+}
+
void cv_lock(struct cond_var *cv)
{
- spin_lock(&cv->lock);
+ spin_lock(cv->lock);
}
void cv_unlock(struct cond_var *cv)
{
- spin_unlock(&cv->lock);
+ spin_unlock(cv->lock);
}
void cv_lock_irqsave(struct cond_var *cv, int8_t *irq_state)
{
unsigned long nr_prev_waiters;
nr_prev_waiters = cv->nr_waiters++;
- spin_unlock(&cv->lock);
+ spin_unlock(cv->lock);
/* Wait til our turn. This forces an ordering of all waiters such that the
* order in which they wait is the order in which they down the sem. */
while (nr_prev_waiters != nr_sem_waiters(&cv->sem))
sem_down(&cv->sem);
}
-/* Comes in locked. Note cv_lock does not disable irqs. */
+/* Comes in locked. Note cv_lock does not disable irqs. They should still be
+ * disabled from the initial cv_lock_irqsave(). */
void cv_wait(struct cond_var *cv)
{
cv_wait_and_unlock(cv);
+ if (cv->irq_okay)
+ assert(!irq_is_enabled());
cv_lock(cv);
}
static void sem_wake_one(struct semaphore *sem)
{
struct kthread *kthread;
+
/* these locks will be irqsaved if the CV is irqsave (only need the one) */
+ debug_lock_semlist();
spin_lock(&sem->lock);
assert(sem->nr_signals < 0);
sem->nr_signals++;
kthread = TAILQ_FIRST(&sem->waiters);
TAILQ_REMOVE(&sem->waiters, kthread, link);
+ debug_upped_sem(sem);
spin_unlock(&sem->lock);
+ debug_unlock_semlist();
kthread_runnable(kthread);
}
void cv_signal(struct cond_var *cv)
{
- spin_lock(&cv->lock);
+ spin_lock(cv->lock);
__cv_signal(cv);
- spin_unlock(&cv->lock);
+ spin_unlock(cv->lock);
}
void cv_broadcast(struct cond_var *cv)
{
- spin_lock(&cv->lock);
+ spin_lock(cv->lock);
__cv_broadcast(cv);
- spin_unlock(&cv->lock);
+ spin_unlock(cv->lock);
}
void cv_signal_irqsave(struct cond_var *cv, int8_t *irq_state)
cv_broadcast(cv);
enable_irqsave(irq_state);
}
+
+/* Helper, aborts and releases a CLE. dereg_ spinwaits on abort_in_progress.
+ * This can throw a PF */
+static void __abort_and_release_cle(struct cv_lookup_elm *cle)
+{
+ int8_t irq_state = 0;
+ /* At this point, we have a handle on the syscall that we want to abort (via
+ * the cle), and we know none of the memory will disappear on us (deregers
+ * wait on the flag). So we'll signal ABORT, which rendez will pick up next
+ * time it is awake. Then we make sure it is awake with a broadcast. */
+ atomic_or(&cle->sysc->flags, SC_ABORT);
+ cmb(); /* flags write before signal; atomic op provided CPU mb */
+ cv_broadcast_irqsave(cle->cv, &irq_state);
+ cmb(); /* broadcast writes before abort flag; atomic op provided CPU mb */
+ atomic_dec(&cle->abort_in_progress);
+}
+
+/* Attempts to abort p's sysc. It will only do so if the sysc lookup succeeds,
+ * so we can handle "guesses" for syscalls that might not be sleeping. This
+ * style of "do it if you know you can" is the best way here - anything else
+ * runs into situations where you don't know if the memory is safe to touch or
+ * not (we're doing a lookup via pointer address, and only dereferencing if that
+ * succeeds). Even something simple like letting userspace write SC_ABORT is
+ * very hard for them, since they don't know a sysc's state for sure (under the
+ * current system).
+ *
+ * Here are the rules:
+ * - if you're flagged SC_ABORT, you don't sleep
+ * - if you sleep, you're on the list
+ * - if you are on the list or abort_in_progress is set, CV is signallable, and
+ * all the memory for CLE is safe */
+bool abort_sysc(struct proc *p, struct syscall *sysc)
+{
+ ERRSTACK(1);
+ struct cv_lookup_elm *cle;
+ int8_t irq_state = 0;
+
+ spin_lock_irqsave(&p->abort_list_lock);
+ TAILQ_FOREACH(cle, &p->abortable_sleepers, link) {
+ if (cle->sysc == sysc) {
+ /* Note: we could have multiple aborters, so we need to use a
+ * numeric refcnt instead of a flag. */
+ atomic_inc(&cle->abort_in_progress);
+ break;
+ }
+ }
+ spin_unlock_irqsave(&p->abort_list_lock);
+ if (!cle)
+ return FALSE;
+ if (!waserror()) /* discard error */
+ __abort_and_release_cle(cle);
+ poperror();
+ return TRUE;
+}
+
+/* This will abort any abortables at the time the call was started for which
+ * should_abort(cle, arg) returns true. New abortables could be registered
+ * concurrently.
+ *
+ * One caller for this is proc_destroy(), in which case DYING_ABORT will be set,
+ * and new abortables will quickly abort and dereg when they see their proc is
+ * DYING_ABORT. */
+static int __abort_all_sysc(struct proc *p,
+ bool (*should_abort)(struct cv_lookup_elm*, void*),
+ void *arg)
+{
+ ERRSTACK(1);
+ struct cv_lookup_elm *cle;
+ int8_t irq_state = 0;
+ struct cv_lookup_tailq abortall_list;
+ uintptr_t old_proc = switch_to(p);
+ int ret = 0;
+
+ /* Concerns: we need to not remove them from their original list, since
+ * concurrent wake ups will cause a dereg, which will remove from the list.
+ * We also can't touch freed memory, so we need a refcnt to keep cles
+ * around. */
+ TAILQ_INIT(&abortall_list);
+ spin_lock_irqsave(&p->abort_list_lock);
+ TAILQ_FOREACH(cle, &p->abortable_sleepers, link) {
+ if (!should_abort(cle, arg))
+ continue;
+ atomic_inc(&cle->abort_in_progress);
+ TAILQ_INSERT_HEAD(&abortall_list, cle, abortall_link);
+ ret++;
+ }
+ spin_unlock_irqsave(&p->abort_list_lock);
+ if (!waserror()) { /* discard error */
+ TAILQ_FOREACH(cle, &abortall_list, abortall_link)
+ __abort_and_release_cle(cle);
+ }
+ poperror();
+ switch_back(p, old_proc);
+ return ret;
+}
+
+static bool always_abort(struct cv_lookup_elm *cle, void *arg)
+{
+ return TRUE;
+}
+
+void abort_all_sysc(struct proc *p)
+{
+ __abort_all_sysc(p, always_abort, 0);
+}
+
+/* cle->sysc could be a bad pointer. we can either use copy_from_user (btw,
+ * we're already in their addr space) or we can use a waserror in
+ * __abort_all_sysc(). Both options are fine. I went with it here for a couple
+ * reasons. It is only this abort function pointer that accesses sysc, though
+ * that could change. Our syscall aborting isn't plugged into a broader error()
+ * handler yet, which means we'd want to poperror instead of nexterror in
+ * __abort_all_sysc, and that would required int ret getting a volatile flag. */
+static bool sysc_uses_fd(struct cv_lookup_elm *cle, void *fd)
+{
+ struct syscall local_sysc;
+ int err;
+
+ err = copy_from_user(&local_sysc, cle->sysc, sizeof(struct syscall));
+ /* Trigger an abort on error */
+ if (err)
+ return TRUE;
+ return syscall_uses_fd(&local_sysc, (int)(long)fd);
+}
+
+int abort_all_sysc_fd(struct proc *p, int fd)
+{
+ return __abort_all_sysc(p, sysc_uses_fd, (void*)(long)fd);
+}
+
+/* Being on the abortable list means that the CLE, KTH, SYSC, and CV are valid
+ * memory. The lock ordering is {CV lock, list_lock}. Callers to this *will*
+ * have CV held. This is done to avoid excessive locking in places like
+ * rendez_sleep, which want to check the condition before registering. */
+void __reg_abortable_cv(struct cv_lookup_elm *cle, struct cond_var *cv)
+{
+ struct per_cpu_info *pcpui = &per_cpu_info[core_id()];
+ cle->cv = cv;
+ cle->kthread = pcpui->cur_kthread;
+ /* Could be a ktask. Can build in support for aborting these later */
+ if (is_ktask(cle->kthread)) {
+ cle->sysc = 0;
+ return;
+ }
+ cle->sysc = cle->kthread->sysc;
+ cle->proc = pcpui->cur_proc;
+ atomic_init(&cle->abort_in_progress, 0);
+ spin_lock_irqsave(&cle->proc->abort_list_lock);
+ TAILQ_INSERT_HEAD(&cle->proc->abortable_sleepers, cle, link);
+ spin_unlock_irqsave(&cle->proc->abort_list_lock);
+}
+
+/* We're racing with the aborter too, who will hold the flag in cle to protect
+ * its ref on our cle. While the lock ordering is CV, list, callers to this
+ * must *not* have the cv lock held. The reason is this waits on a successful
+ * abort_sysc, which is trying to cv_{signal,broadcast}, which could wait on the
+ * CV lock. So if we hold the CV lock, we can deadlock (circular dependency).*/
+void dereg_abortable_cv(struct cv_lookup_elm *cle)
+{
+ if (is_ktask(cle->kthread))
+ return;
+ assert(cle->proc);
+ spin_lock_irqsave(&cle->proc->abort_list_lock);
+ TAILQ_REMOVE(&cle->proc->abortable_sleepers, cle, link);
+ spin_unlock_irqsave(&cle->proc->abort_list_lock);
+ /* If we won the race and yanked it out of the list before abort claimed it,
+ * this will already be FALSE. */
+ while (atomic_read(&cle->abort_in_progress))
+ cpu_relax();
+}
+
+/* Helper to sleepers to know if they should abort or not. I'll probably extend
+ * this with things for ktasks in the future. */
+bool should_abort(struct cv_lookup_elm *cle)
+{
+ struct syscall local_sysc;
+ int err;
+
+ if (is_ktask(cle->kthread))
+ return FALSE;
+ if (cle->proc && (cle->proc->state == PROC_DYING_ABORT))
+ return TRUE;
+ if (cle->sysc) {
+ assert(cle->proc && (cle->proc == current));
+ err = copy_from_user(&local_sysc, cle->sysc,
+ offsetof(struct syscall, flags) +
+ sizeof(cle->sysc->flags));
+ /* just go ahead and abort if there was an error */
+ if (err || (atomic_read(&local_sysc.flags) & SC_ABORT))
+ return TRUE;
+ }
+ return FALSE;
+}
+
+/* Sometimes the kernel needs to switch out of process context and into a
+ * 'process-less' kernel thread. This is basically a ktask. We use this mostly
+ * when performing file ops as the kernel. It's nasty, and all uses of this
+ * probably should be removed. (TODO: KFOP). */
+uintptr_t switch_to_ktask(void)
+{
+ struct per_cpu_info *pcpui = &per_cpu_info[core_id()];
+ struct kthread *kth = pcpui->cur_kthread;
+
+ if (is_ktask(kth))
+ return 0;
+ /* We leave the SAVE_ADDR_SPACE flag on. Now we're basically a ktask that
+ * cares about its addr space, since we need to return to it (not that we're
+ * leaving). */
+ kth->flags |= KTH_IS_KTASK;
+ return 1;
+}
+
+void switch_back_from_ktask(uintptr_t old_ret)
+{
+ struct per_cpu_info *pcpui = &per_cpu_info[core_id()];
+ struct kthread *kth = pcpui->cur_kthread;
+
+ if (old_ret)
+ kth->flags &= ~KTH_IS_KTASK;
+}
projects / akaros.git / blobdiff