kern/include/rwlock.h

   1 /* Copyright (c) 2013 The Regents of the University of California
   2  * Barret Rhoden <brho@cs.berkeley.edu>
   3  * See LICENSE for details.
   4  *
   5  * Reader-writer queue locks (sleeping locks).
   6  *
   7  * Readers favor readers; writers favor writers.  Check out rwlock.c for more
   8  * info.
   9  *
  10  * One consequence of this: "if some reader holds a rwlock, then any other
  11  * thread (including itself) can get an rlock". */
  12
  13 #pragma once
  14
  15 #include <ros/common.h>
  16 #include <kthread.h>
  17 #include <atomic.h>
  18
  19 struct rwlock {
  20         spinlock_t                                      lock;
  21         atomic_t                                        nr_readers;
  22         bool                                            writing;
  23         struct cond_var                         readers;
  24         struct cond_var                         writers;
  25 };
  26 typedef struct rwlock rwlock_t;
  27
  28 void rwinit(struct rwlock *rw_lock);
  29 void rlock(struct rwlock *rw_lock);
  30 bool canrlock(struct rwlock *rw_lock);
  31 void runlock(struct rwlock *rw_lock);
  32 void wlock(struct rwlock *rw_lock);
  33 void wunlock(struct rwlock *rw_lock);