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[sanitizer] Use private futex operations for BlockingMutex 

Summary:
Use `FUTEX_PRIVATE_FLAG` in conjunction with the wait & wake operations
employed by `BlockingMutex`. As far as I can tell, the mutexes are
process-private, and there is an actual performance benefit at employing the
private operations. There should be no downside to switching to it.

Reviewers: eugenis, alekseyshl, dvyukov

Reviewed By: dvyukov

Subscribers: kubamracek, delcypher, #sanitizers, llvm-commits

Differential Revision: https://reviews.llvm.org/D50910

llvm-svn: 340178
This commit is contained in:
Kostya Kortchinsky 2018-08-20 14:57:58 +00:00
parent 0875e759f0
commit 7515e75bc2
1 changed files with 6 additions and 2 deletions
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8
compiler-rt/lib/sanitizer_common/sanitizer_linux.cc
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@ -117,6 +117,9 @@ struct kernel_timeval {
// <linux/futex.h> is broken on some linux distributions.
const int FUTEX_WAIT = 0;
const int FUTEX_WAKE = 1;
const int FUTEX_PRIVATE_FLAG = 128;
const int FUTEX_WAIT_PRIVATE = FUTEX_WAIT | FUTEX_PRIVATE_FLAG;
const int FUTEX_WAKE_PRIVATE = FUTEX_WAKE | FUTEX_PRIVATE_FLAG;
#endif // SANITIZER_LINUX
// Are we using 32-bit or 64-bit Linux syscalls?
@ -686,7 +689,8 @@ void BlockingMutex::Lock() {
#elif SANITIZER_NETBSD
sched_yield(); /* No userspace futex-like synchronization */
#else
internal_syscall(SYSCALL(futex), (uptr)m, FUTEX_WAIT, MtxSleeping, 0, 0, 0);
internal_syscall(SYSCALL(futex), (uptr)m, FUTEX_WAIT_PRIVATE, MtxSleeping,
0, 0, 0);
#endif
}
}
@ -701,7 +705,7 @@ void BlockingMutex::Unlock() {
#elif SANITIZER_NETBSD
/* No userspace futex-like synchronization */
#else
internal_syscall(SYSCALL(futex), (uptr)m, FUTEX_WAKE, 1, 0, 0, 0);
internal_syscall(SYSCALL(futex), (uptr)m, FUTEX_WAKE_PRIVATE, 1, 0, 0, 0);
#endif
}
}