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Fix Mellanox copyright. #8

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Fix Mellanox copyright. #8

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d204f67
opal/sync: fix race condition
hjelmn Jun 24, 2016
9ba03dc
Fix Mellanox copyright.
artpol84 Jun 26, 2016
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22 changes: 20 additions & 2 deletions opal/threads/wait_sync.h
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@
* reserved.
* Copyright (c) 2016 Los Alamos National Security, LLC. All rights
* reserved.
* Copyright (c) 2016 Mellanox Technologies. All rights reserved.
* $COPYRIGHT$
*
* Additional copyrights may follow
Expand All @@ -24,24 +25,37 @@ typedef struct ompi_wait_sync_t {
pthread_mutex_t lock;
struct ompi_wait_sync_t *next;
struct ompi_wait_sync_t *prev;
volatile bool signaling;
} ompi_wait_sync_t;

#define REQUEST_PENDING (void*)0L
#define REQUEST_COMPLETED (void*)1L

#define SYNC_WAIT(sync) (opal_using_threads() ? sync_wait_mt (sync) : sync_wait_st (sync))

/* The loop in release handles a race condition between the signaling
* thread and the destruction of the condition variable. The signaling
* member will be set to false after the final signaling thread has
* finished opertating on the sync object. This is done to avoid
* extra atomics in the singalling function and keep it as fast
* as possible. Note that the race window is small so spinning here
* is more optimal than sleeping since this macro is called in
* the critical path. */
#define WAIT_SYNC_RELEASE(sync) \
if (opal_using_threads()) { \
pthread_cond_destroy(&(sync)->condition); \
pthread_mutex_destroy(&(sync)->lock); \
while ((sync)->signaling) { \
continue; \
} \
pthread_cond_destroy(&(sync)->condition); \
pthread_mutex_destroy(&(sync)->lock); \
}

#define WAIT_SYNC_SIGNAL(sync) \
if (opal_using_threads()) { \
pthread_mutex_lock(&(sync->lock)); \
pthread_cond_signal(&sync->condition); \
pthread_mutex_unlock(&(sync->lock)); \
sync->signaling = false; \
}

OPAL_DECLSPEC int sync_wait_mt(ompi_wait_sync_t *sync);
Expand All @@ -61,6 +75,7 @@ static inline int sync_wait_st (ompi_wait_sync_t *sync)
(sync)->next = NULL; \
(sync)->prev = NULL; \
(sync)->status = 0; \
(sync)->signaling = false; \
if (opal_using_threads()) { \
pthread_cond_init (&(sync)->condition, NULL); \
pthread_mutex_init (&(sync)->lock, NULL); \
Expand All @@ -75,6 +90,9 @@ static inline int sync_wait_st (ompi_wait_sync_t *sync)
*/
static inline void wait_sync_update(ompi_wait_sync_t *sync, int updates, int status)
{
sync->signaling = true;
/* ensure the signalling value is commited before updating the count */
opal_atomic_wmb ();
if( OPAL_LIKELY(OPAL_SUCCESS == status) ) {
if( 0 != (OPAL_THREAD_ADD32(&sync->count, -updates)) ) {
return;
Expand Down