diff options
author | Thiago Macieira <thiago.macieira@intel.com> | 2012-08-11 14:08:39 +0200 |
---|---|---|
committer | Qt by Nokia <qt-info@nokia.com> | 2012-09-14 03:45:50 +0200 |
commit | 870bd84a4ee53ea98fd232da18771b1525dac1a1 (patch) | |
tree | b4f473f26f944352aeb2874ae61371183b5332d7 | |
parent | 3acaa648f0ffd03c4695d0be7ed25e73724e4417 (diff) |
Don't recheck about timeout == 0 during mutex locking
If the timeout wasn't zero, it can only become zero if we return from
futex() with a non-timeout reason but subsequently expires while we're
recalculating something.
A side effect is that we try-lock a non-recursive mutex exactly
once. Before this change, we'd fastTryLock() twice even with
timeout == 0.
Change-Id: I0af09fc2a84669a683a843fcf1513203b075dfb7
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
-rw-r--r-- | src/corelib/thread/qmutex_linux.cpp | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/src/corelib/thread/qmutex_linux.cpp b/src/corelib/thread/qmutex_linux.cpp index e14660cc37..09db046f0f 100644 --- a/src/corelib/thread/qmutex_linux.cpp +++ b/src/corelib/thread/qmutex_linux.cpp @@ -123,17 +123,18 @@ bool QBasicMutex::lockInternal(int timeout) Q_DECL_NOTHROW return static_cast<QRecursiveMutexPrivate *>(d)->lock(timeout); } + if (timeout == 0) + return false; + QElapsedTimer elapsedTimer; if (timeout >= 1) elapsedTimer.start(); while (!fastTryLock()) { d = d_ptr.load(); + if (!d) // if d is 0, the mutex is unlocked continue; - if (timeout == 0) - return false; - // the mutex is locked already, set a bit indicating we're waiting while (d_ptr.fetchAndStoreAcquire(dummyFutexValue()) != 0) { struct timespec ts, *pts = 0; |