Magic-Mirror/llvm-capstone
1
0
Fork 0
mirror of https://github.com/capstone-engine/llvm-capstone.git synced 2025-01-15 12:39:19 +00:00
Code Issues Actions 4 Packages Projects Releases Wiki Activity

tsan: don't use spinning in __cxa_guard_acquire/pthread_once

Browse Source 
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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp
View File

@ -853,6 +853,7 @@ TSAN_INTERCEPTOR(int, posix_memalign, void **memptr, uptr align, uptr sz) {
constexpr u32 kGuardInit = 0; constexpr u32 kGuardInit = 0;
constexpr u32 kGuardDone = 1; constexpr u32 kGuardDone = 1;
constexpr u32 kGuardRunning = 1 << 16; constexpr u32 kGuardRunning = 1 << 16;
constexpr u32 kGuardWaiter = 1 << 17;
static int guard_acquire(ThreadState *thr, uptr pc, atomic_uint32_t *g) { static int guard_acquire(ThreadState *thr, uptr pc, atomic_uint32_t *g) {
OnPotentiallyBlockingRegionBegin(); OnPotentiallyBlockingRegionBegin();
@ -868,7 +869,10 @@ static int guard_acquire(ThreadState *thr, uptr pc, atomic_uint32_t *g) {
Acquire(thr, pc, (uptr)g); Acquire(thr, pc, (uptr)g);
return 0; return 0;
} else { } 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) { static void guard_release(ThreadState *thr, uptr pc, atomic_uint32_t *g) {
if (!thr->in_ignored_lib) if (!thr->in_ignored_lib)
Release(thr, pc, (uptr)g); 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 - // __cxa_guard_acquire and friends need to be intercepted in a special way -