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authorThiago Macieira <thiago.macieira@intel.com>2016-04-29 21:39:44 -0700
committerThiago Macieira <thiago.macieira@intel.com>2016-05-11 22:22:50 +0000
commit9ef59b586d6c65404835c5003a0f486ef9e162c3 (patch)
tree1ec1860b86f5e10cf2a91b37647987d13e0026a8 /src/corelib
parente2e0dfee7c675c91132197b4a01a394a5da9a36f (diff)
QMutex: make FUTEX_PRIVATE_FLAG a mandatory feature
The flag was introduced in kernel 2.6.22, but we're already depending on features added on 2.6.23 in qcore_unix_p.h (pipe2, dup3, O_CLOEXEC) and 2.6.27 in qnet_unix_p.h (accept4 and SOCK_CLOEXEC). Change-Id: Id5480807d25e49e78b79ffff144a093c9e30cd96 Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com> Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Diffstat (limited to 'src/corelib')
-rw-r--r--src/corelib/thread/qmutex_linux.cpp41
1 files changed, 6 insertions, 35 deletions
diff --git a/src/corelib/thread/qmutex_linux.cpp b/src/corelib/thread/qmutex_linux.cpp
index 89eb3da203..25444ffff6 100644
--- a/src/corelib/thread/qmutex_linux.cpp
+++ b/src/corelib/thread/qmutex_linux.cpp
@@ -56,6 +56,11 @@
# error "Qt build is broken: qmutex_linux.cpp is being built but futex support is not wanted"
#endif
+#ifndef FUTEX_PRIVATE_FLAG
+# define FUTEX_PRIVATE_FLAG 128
+#endif
+
+
QT_BEGIN_NAMESPACE
/*
@@ -104,40 +109,6 @@ QT_BEGIN_NAMESPACE
static QBasicAtomicInt futexFlagSupport = Q_BASIC_ATOMIC_INITIALIZER(-1);
-static int checkFutexPrivateSupport()
-{
- int value = 0;
-#if defined(FUTEX_PRIVATE_FLAG)
- // check if the kernel supports extra futex flags
- // FUTEX_PRIVATE_FLAG appeared in v2.6.22
- Q_STATIC_ASSERT(FUTEX_PRIVATE_FLAG != 0x80000000);
-
- // try an operation that has no side-effects: wake up 42 threads
- // futex will return -1 (errno==ENOSYS) if the flag isn't supported
- // there should be no other error conditions
- value = syscall(__NR_futex, &futexFlagSupport,
- FUTEX_WAKE | FUTEX_PRIVATE_FLAG,
- 42, 0, 0, 0);
- if (value != -1)
- value = FUTEX_PRIVATE_FLAG;
- else
- value = 0;
-
-#else
- value = 0;
-#endif
- futexFlagSupport.store(value);
- return value;
-}
-
-static inline int futexFlags()
-{
- int value = futexFlagSupport.load();
- if (Q_LIKELY(value != -1))
- return value;
- return checkFutexPrivateSupport();
-}
-
static inline int _q_futex(void *addr, int op, int val, const struct timespec *timeout) Q_DECL_NOTHROW
{
volatile int *int_addr = reinterpret_cast<volatile int *>(addr);
@@ -149,7 +120,7 @@ static inline int _q_futex(void *addr, int op, int val, const struct timespec *t
// we use __NR_futex because some libcs (like Android's bionic) don't
// provide SYS_futex etc.
- return syscall(__NR_futex, int_addr, op | futexFlags(), val, timeout, addr2, val2);
+ return syscall(__NR_futex, int_addr, op | FUTEX_PRIVATE_FLAG, val, timeout, addr2, val2);
}
static inline QMutexData *dummyFutexValue()