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 #ifndef ROS_KERN_RWLOCK_H
  14 #define ROS_KERN_RWLOCK_H
  15
  16 #include <ros/common.h>
  17 #include <kthread.h>
  18 #include <atomic.h>
  19
  20 struct rwlock {
  21         spinlock_t                                      lock;
  22         atomic_t                                        nr_readers;
  23         bool                                            writing;
  24         struct cond_var                         readers;
  25         struct cond_var                         writers;
  26 };
  27 typedef struct rwlock rwlock_t;
  28
  29 void rwinit(struct rwlock *rw_lock);
  30 void rlock(struct rwlock *rw_lock);
  31 bool canrlock(struct rwlock *rw_lock);
  32 void runlock(struct rwlock *rw_lock);
  33 void wlock(struct rwlock *rw_lock);
  34 void wunlock(struct rwlock *rw_lock);
  35
  36 #endif /* ROS_KERN_RWLOCK_H */