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[tsan] Fix pthread_once() on Mac OS X
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Change 636428c enabled BlockingRegion hooks for pthread_once().
Unfortunately this seems to cause crashes on Mac OS X which uses
pthread_once() from locations that seem to result in crashes:

| ThreadSanitizer:DEADLYSIGNAL
| ==31465==ERROR: ThreadSanitizer: stack-overflow on address 0x7ffee73fffd8 (pc 0x00010807fd2a bp 0x7ffee7400050 sp 0x7ffee73fffb0 T93815)
|     #0 __tsan::MetaMap::GetSync(__tsan::ThreadState*, unsigned long, unsigned long, bool, bool) tsan_sync.cpp:195 (libclang_rt.tsan_osx_dynamic.dylib:x86_64+0x78d2a)
|     #1 __tsan::MutexPreLock(__tsan::ThreadState*, unsigned long, unsigned long, unsigned int) tsan_rtl_mutex.cpp:143 (libclang_rt.tsan_osx_dynamic.dylib:x86_64+0x6cefc)
|     rust-lang#2 wrap_pthread_mutex_lock sanitizer_common_interceptors.inc:4240 (libclang_rt.tsan_osx_dynamic.dylib:x86_64+0x3dae0)
|     rust-lang#3 flockfile <null>:2 (libsystem_c.dylib:x86_64+0x38a69)
|     rust-lang#4 puts <null>:2 (libsystem_c.dylib:x86_64+0x3f69b)
|     rust-lang#5 wrap_puts sanitizer_common_interceptors.inc (libclang_rt.tsan_osx_dynamic.dylib:x86_64+0x34d83)
|     rust-lang#6 __tsan::OnPotentiallyBlockingRegionBegin() cxa_guard_acquire.cpp:8 (foo:x86_64+0x100000e48)
|     rust-lang#7 wrap_pthread_once tsan_interceptors_posix.cpp:1512 (libclang_rt.tsan_osx_dynamic.dylib:x86_64+0x2f6e6)

From the stack trace it can be seen that the caller is unknown, and the
resulting stack-overflow seems to indicate that whoever the caller is
does not have enough stack space or otherwise is running in a limited
environment not yet ready for full instrumentation.

Fix it by reverting behaviour on Mac OS X to not call BlockingRegion
hooks from pthread_once().

Reported-by: azharudd

Reviewed By: glider

Differential Revision: https://reviews.llvm.org/D108305
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melver committed Aug 19, 2021
1 parent c20cb55 commit 303d278
Showing 1 changed file with 12 additions and 4 deletions.
16 changes: 12 additions & 4 deletions compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -855,9 +855,15 @@ 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();
auto on_exit = at_scope_exit(&OnPotentiallyBlockingRegionEnd);
static int guard_acquire(ThreadState *thr, uptr pc, atomic_uint32_t *g,
bool blocking_hooks = true) {
if (blocking_hooks)
OnPotentiallyBlockingRegionBegin();
auto on_exit = at_scope_exit([blocking_hooks] {
if (blocking_hooks)
OnPotentiallyBlockingRegionEnd();
});

for (;;) {
u32 cmp = atomic_load(g, memory_order_acquire);
if (cmp == kGuardInit) {
Expand Down Expand Up @@ -1509,7 +1515,9 @@ TSAN_INTERCEPTOR(int, pthread_once, void *o, void (*f)()) {
else
a = static_cast<atomic_uint32_t*>(o);

if (guard_acquire(thr, pc, a)) {
// Mac OS X appears to use pthread_once() where calling BlockingRegion hooks
// result in crashes due to too little stack space.
if (guard_acquire(thr, pc, a, !SANITIZER_MAC)) {
(*f)();
guard_release(thr, pc, a);
}
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