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| author | Sergei Golubchik <sergii@pisem.net> | 2011-07-02 22:08:51 +0200 |
|---|---|---|
| committer | Sergei Golubchik <sergii@pisem.net> | 2011-07-02 22:08:51 +0200 |
| commit | 9809f05199aeb0b67991fac41bd86f38730768dc (patch) | |
| tree | fa2792ff86d0da014b535d743759810612338042 /mysys/my_winthread.c | |
| parent | 0accbd0364e0333e0b119aa9ce93e34ded9df6cb (diff) | |
| parent | 5a0e7394a5ae0c7b6a1ea35b7ea3a8985325987a (diff) | |
| download | mariadb-git-9809f05199aeb0b67991fac41bd86f38730768dc.tar.gz | |
5.5-merge
Diffstat (limited to 'mysys/my_winthread.c')
| -rw-r--r-- | mysys/my_winthread.c | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/mysys/my_winthread.c b/mysys/my_winthread.c index 19d4a707062..54b8463fe0b 100644 --- a/mysys/my_winthread.c +++ b/mysys/my_winthread.c @@ -156,8 +156,19 @@ int pthread_cancel(pthread_t thread) int my_pthread_once(my_pthread_once_t *once_control, void (*init_routine)(void)) { - LONG state= InterlockedCompareExchange(once_control, MY_PTHREAD_ONCE_INPROGRESS, - MY_PTHREAD_ONCE_INIT); + LONG state; + + /* + Do "dirty" read to find out if initialization is already done, to + save an interlocked operation in common case. Memory barriers are ensured by + Visual C++ volatile implementation. + */ + if (*once_control == MY_PTHREAD_ONCE_DONE) + return 0; + + state= InterlockedCompareExchange(once_control, MY_PTHREAD_ONCE_INPROGRESS, + MY_PTHREAD_ONCE_INIT); + switch(state) { case MY_PTHREAD_ONCE_INIT: |