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tsan: don't use spinning in __cxa_guard_acquire/pthread_once

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Currently we use passive spinning with internal_sched_yield to wait
in __cxa_guard_acquire/pthread_once. Passive spinning tends to degrade
ungracefully under high load. Use FutexWait/Wake instead.

Depends on D107359.

Reviewed By: vitalybuka, melver

Differential Revision: https://reviews.llvm.org/D107360
This commit is contained in:
Dmitry Vyukov 2021-08-03 17:18:06 +02:00
parent 2718ae397b
commit e3f4c63e78
1 changed files with 8 additions and 2 deletions
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10
compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp
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@ -853,6 +853,7 @@ TSAN_INTERCEPTOR(int, posix_memalign, void **memptr, uptr align, uptr sz) {
constexpr u32 kGuardInit = 0;
constexpr u32 kGuardDone = 1;
constexpr u32 kGuardRunning = 1 << 16;
constexpr u32 kGuardWaiter = 1 << 17;
static int guard_acquire(ThreadState *thr, uptr pc, atomic_uint32_t *g) {
OnPotentiallyBlockingRegionBegin();
@ -868,7 +869,10 @@ static int guard_acquire(ThreadState *thr, uptr pc, atomic_uint32_t *g) {
Acquire(thr, pc, (uptr)g);
return 0;
} else {
internal_sched_yield();
if ((cmp & kGuardWaiter) ||
atomic_compare_exchange_strong(g, &cmp, cmp | kGuardWaiter,
memory_order_relaxed))
FutexWait(g, cmp | kGuardWaiter);
}
}
}
@ -876,7 +880,9 @@ static int guard_acquire(ThreadState *thr, uptr pc, atomic_uint32_t *g) {
static void guard_release(ThreadState *thr, uptr pc, atomic_uint32_t *g) {
if (!thr->in_ignored_lib)
Release(thr, pc, (uptr)g);
atomic_store(g, kGuardDone, memory_order_release);
u32 old = atomic_exchange(g, kGuardDone, memory_order_release);
if (old & kGuardWaiter)
FutexWake(g, 1 << 30);
}
// __cxa_guard_acquire and friends need to be intercepted in a special way -