BUG#30992 (Wrong implementation of pthread_mutex_trylock()):

Adding support for correct handling of pthread_mutex_trylock() on Win32
systems as well as when using the safe mutexes. 


include/my_pthread.h:
  Adding win_pthread_mutex_trylock() function as wrapper function for
  Windows implementation of pthread_mutex_trylock().
  
  Adding flag to safe_mutex_lock() that is shall not abort if the mutex
  is already locked and instead return EBUSY since this is the POSIX
  behaviour.
mysys/my_winthread.c:
  Added Win32 wrappper function to handle pthread_mutex_trylock().
mysys/thr_mutex.c:
  Added parameter 'try_lock' to safe_mutex_lock() to allow it to do double-
  duty as a pthread_mutex_trylock() in addition to working as
  pthread_mutex_lock().
  
  The code needs to return EBUSY instead of throwing an error in the event
  that the mutex is re-locked (we do not have recursive mutexes), but it
  also requires some special handling to avoid race conditions when
  calling the real pthread_mutex_{lock,trylock}().

1 files changed, 5 insertions, 4 deletions

diff --git a/include/my_pthread.h b/include/my_pthread.h
index d64b5348666..e28bb9df1f3 100644
--- a/include/my_pthread.h
+++ b/include/my_pthread.h
@@ -135,6 +135,7 @@ struct timespec {
 
 void win_pthread_init(void);
 int win_pthread_setspecific(void *A,void *B,uint length);
+int win_pthread_mutex_trylock(pthread_mutex_t *mutex);
 int pthread_create(pthread_t *,pthread_attr_t *,pthread_handler,void *);
 int pthread_cond_init(pthread_cond_t *cond, const pthread_condattr_t *attr);
 int pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex);
@@ -195,7 +196,7 @@ extern int pthread_mutex_destroy (pthread_mutex_t *);
 #else
 #define pthread_mutex_init(A,B)  (InitializeCriticalSection(A),0)
 #define pthread_mutex_lock(A)	 (EnterCriticalSection(A),0)
-#define pthread_mutex_trylock(A) (WaitForSingleObject((A), 0) == WAIT_TIMEOUT)
+#define pthread_mutex_trylock(A) win_pthread_mutex_trylock((A))
 #define pthread_mutex_unlock(A)  LeaveCriticalSection(A)
 #define pthread_mutex_destroy(A) DeleteCriticalSection(A)
 #define my_pthread_setprio(A,B)  SetThreadPriority(GetCurrentThread(), (B))
@@ -593,7 +594,7 @@ typedef struct st_safe_mutex_info_t
 
 int safe_mutex_init(safe_mutex_t *mp, const pthread_mutexattr_t *attr,
                     const char *file, uint line);
-int safe_mutex_lock(safe_mutex_t *mp,const char *file, uint line);
+int safe_mutex_lock(safe_mutex_t *mp, my_bool try_lock, const char *file, uint line);
 int safe_mutex_unlock(safe_mutex_t *mp,const char *file, uint line);
 int safe_mutex_destroy(safe_mutex_t *mp,const char *file, uint line);
 int safe_cond_wait(pthread_cond_t *cond, safe_mutex_t *mp,const char *file,
@@ -616,12 +617,12 @@ void safe_mutex_end(FILE *file);
 #undef pthread_cond_timedwait
 #undef pthread_mutex_trylock
 #define pthread_mutex_init(A,B) safe_mutex_init((A),(B),__FILE__,__LINE__)
-#define pthread_mutex_lock(A) safe_mutex_lock((A),__FILE__,__LINE__)
+#define pthread_mutex_lock(A) safe_mutex_lock((A), FALSE, __FILE__, __LINE__)
 #define pthread_mutex_unlock(A) safe_mutex_unlock((A),__FILE__,__LINE__)
 #define pthread_mutex_destroy(A) safe_mutex_destroy((A),__FILE__,__LINE__)
 #define pthread_cond_wait(A,B) safe_cond_wait((A),(B),__FILE__,__LINE__)
 #define pthread_cond_timedwait(A,B,C) safe_cond_timedwait((A),(B),(C),__FILE__,__LINE__)
-#define pthread_mutex_trylock(A) pthread_mutex_lock(A)
+#define pthread_mutex_trylock(A) safe_mutex_lock((A), TRUE, __FILE__, __LINE__)
 #define pthread_mutex_t safe_mutex_t
 #define safe_mutex_assert_owner(mp) \
           DBUG_ASSERT((mp)->count > 0 && \