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tsan: fix and test detection of TLS races

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Currently detection of races with TLS/stack initialization
is broken because we imitate the write before thread initialization,
so it's modelled with a wrong thread/epoch.
Fix that and add a test.

Reviewed By: melver

Differential Revision: https://reviews.llvm.org/D110538
This commit is contained in:
Dmitry Vyukov 2021-09-27 13:43:33 +02:00
parent bf980930e5
commit b4c1e5cb73
3 changed files with 51 additions and 10 deletions
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9
compiler-rt/lib/tsan/rtl/tsan_platform_linux.cpp
View file

@ -453,6 +453,8 @@ static void InitializeLongjmpXorKey() {
}
#endif
extern "C" void __tsan_tls_initialization() {}
void ImitateTlsWrite(ThreadState *thr, uptr tls_addr, uptr tls_size) {
// Check that the thr object is in tls;
const uptr thr_beg = (uptr)thr;
@ -462,9 +464,10 @@ void ImitateTlsWrite(ThreadState *thr, uptr tls_addr, uptr tls_size) {
CHECK_GE(thr_end, tls_addr);
CHECK_LE(thr_end, tls_addr + tls_size);
// Since the thr object is huge, skip it.
MemoryRangeImitateWrite(thr, /*pc=*/2, tls_addr, thr_beg - tls_addr);
MemoryRangeImitateWrite(thr, /*pc=*/2, thr_end,
tls_addr + tls_size - thr_end);
const uptr pc = StackTrace::GetNextInstructionPc(
reinterpret_cast<uptr>(__tsan_tls_initialization));
MemoryRangeImitateWrite(thr, pc, tls_addr, thr_beg - tls_addr);
MemoryRangeImitateWrite(thr, pc, thr_end, tls_addr + tls_size - thr_end);
}
// Note: this function runs with async signals enabled,

17
compiler-rt/lib/tsan/rtl/tsan_rtl_thread.cpp
View file

@ -156,13 +156,6 @@ void ThreadStart(ThreadState *thr, Tid tid, tid_t os_id,
if (thread_type != ThreadType::Fiber)
GetThreadStackAndTls(tid == kMainTid, &stk_addr, &stk_size, &tls_addr,
&tls_size);
if (tid != kMainTid) {
if (stk_addr && stk_size)
MemoryRangeImitateWrite(thr, /*pc=*/ 1, stk_addr, stk_size);
if (tls_addr && tls_size) ImitateTlsWrite(thr, tls_addr, tls_size);
}
#endif
ThreadRegistry *tr = &ctx->thread_registry;
@ -178,6 +171,16 @@ void ThreadStart(ThreadState *thr, Tid tid, tid_t os_id,
ThreadIgnoreSyncBegin(thr, 0);
}
#endif
#if !SANITIZER_GO
if (tid != kMainTid) {
if (stk_addr && stk_size)
MemoryRangeImitateWrite(thr, /*pc=*/1, stk_addr, stk_size);
if (tls_addr && tls_size)
ImitateTlsWrite(thr, tls_addr, tls_size);
}
#endif
}
void ThreadContext::OnStarted(void *arg) {

35
compiler-rt/test/tsan/tls_race3.cpp Normal file
View file

@ -0,0 +1,35 @@
// RUN: %clangxx_tsan %darwin_min_target_with_tls_support -O1 %s -o %t && \
// RUN: %deflake %run %t | FileCheck %s
// Race with initial TLS initialization:
// there is no explicit second write,
// but the TLS variable is published unsafely.
#include "test.h"
__thread long X;
long *P;
void *Thread(void *a) {
__atomic_store_n(&P, &X, __ATOMIC_RELAXED);
barrier_wait(&barrier);
barrier_wait(&barrier);
return 0;
}
int main() {
barrier_init(&barrier, 2);
pthread_t t;
pthread_create(&t, NULL, Thread, NULL);
barrier_wait(&barrier);
long *p = __atomic_load_n(&P, __ATOMIC_RELAXED);
*p = 42;
barrier_wait(&barrier);
pthread_join(t, 0);
}
// CHECK: WARNING: ThreadSanitizer: data race
// CHECK: Write of size 8 at {{.*}} by main thread:
// CHECK: #0 main
// CHECK: Previous write of size 8 at {{.*}} by thread T1:
// CHECK: #0 __tsan_tls_initialization
// CHECK: Location is TLS of thread T1.