tsan: fix another potential deadlock in fork

Linux/fork_deadlock.cpp currently hangs in debug mode in the following stack.
Disable memory access handling in OnUserAlloc/Free around fork.

1  0x000000000042c54b in __sanitizer::internal_sched_yield () at sanitizer_linux.cpp:452
2  0x000000000042da15 in __sanitizer::StaticSpinMutex::LockSlow (this=0x57ef02 <__sanitizer::internal_allocator_cache_mu>) at sanitizer_mutex.cpp:24
3  0x0000000000423927 in __sanitizer::StaticSpinMutex::Lock (this=0x57ef02 <__sanitizer::internal_allocator_cache_mu>) at sanitizer_mutex.h:32
4  0x000000000042354c in __sanitizer::GenericScopedLock<__sanitizer::StaticSpinMutex>::GenericScopedLock (this=this@entry=0x7ffcabfca0b8, mu=0x1) at sanitizer_mutex.h:367
5  0x0000000000423653 in __sanitizer::RawInternalAlloc (size=size@entry=72, cache=cache@entry=0x0, alignment=8, alignment@entry=0) at sanitizer_allocator.cpp:52
6  0x00000000004235e9 in __sanitizer::InternalAlloc (size=size@entry=72, cache=0x1, cache@entry=0x0, alignment=4, alignment@entry=0) at sanitizer_allocator.cpp:86
7  0x000000000043aa15 in __sanitizer::SymbolizedStack::New (addr=4802655) at sanitizer_symbolizer.cpp:45
8  0x000000000043b353 in __sanitizer::Symbolizer::SymbolizePC (this=0x7f578b77a028, addr=4802655) at sanitizer_symbolizer_libcdep.cpp:90
9  0x0000000000439dbe in __sanitizer::(anonymous namespace)::StackTraceTextPrinter::ProcessAddressFrames (this=this@entry=0x7ffcabfca208, pc=4802655) at sanitizer_stacktrace_libcdep.cpp:36
10 0x0000000000439c89 in __sanitizer::StackTrace::PrintTo (this=this@entry=0x7ffcabfca2a0, output=output@entry=0x7ffcabfca260) at sanitizer_stacktrace_libcdep.cpp:109
11 0x0000000000439fe0 in __sanitizer::StackTrace::Print (this=0x18) at sanitizer_stacktrace_libcdep.cpp:132
12 0x0000000000495359 in __sanitizer::PrintMutexPC (pc=4802656) at tsan_rtl.cpp:774
13 0x000000000042e0e4 in __sanitizer::InternalDeadlockDetector::Lock (this=0x7f578b1ca740, type=type@entry=2, pc=pc@entry=4371612) at sanitizer_mutex.cpp:177
14 0x000000000042df65 in __sanitizer::CheckedMutex::LockImpl (this=<optimized out>, pc=4) at sanitizer_mutex.cpp:218
15 0x000000000042bc95 in __sanitizer::CheckedMutex::Lock (this=0x600001000000) at sanitizer_mutex.h:127
16 __sanitizer::Mutex::Lock (this=0x600001000000) at sanitizer_mutex.h:165
17 0x000000000042b49c in __sanitizer::GenericScopedLock<__sanitizer::Mutex>::GenericScopedLock (this=this@entry=0x7ffcabfca370, mu=0x1) at sanitizer_mutex.h:367
18 0x000000000049504f in __tsan::TraceSwitch (thr=0x7f578b1ca980) at tsan_rtl.cpp:656
19 0x000000000049523e in __tsan_trace_switch () at tsan_rtl.cpp:683
20 0x0000000000499862 in __tsan::TraceAddEvent (thr=0x7f578b1ca980, fs=..., typ=__tsan::EventTypeMop, addr=4499472) at tsan_rtl.h:624
21 __tsan::MemoryAccessRange (thr=0x7f578b1ca980, pc=4499472, addr=135257110102784, size=size@entry=16, is_write=true) at tsan_rtl_access.cpp:563
22 0x000000000049853a in __tsan::MemoryRangeFreed (thr=thr@entry=0x7f578b1ca980, pc=pc@entry=4499472, addr=addr@entry=135257110102784, size=16) at tsan_rtl_access.cpp:487
23 0x000000000048f6bf in __tsan::OnUserFree (thr=thr@entry=0x7f578b1ca980, pc=pc@entry=4499472, p=p@entry=135257110102784, write=true) at tsan_mman.cpp:260
24 0x000000000048f61f in __tsan::user_free (thr=thr@entry=0x7f578b1ca980, pc=4499472, p=p@entry=0x7b0400004300, signal=true) at tsan_mman.cpp:213
25 0x000000000044a820 in __interceptor_free (p=0x7b0400004300) at tsan_interceptors_posix.cpp:708
26 0x00000000004ad599 in alloc_free_blocks () at fork_deadlock.cpp:25
27 __tsan_test_only_on_fork () at fork_deadlock.cpp:32
28 0x0000000000494870 in __tsan::ForkBefore (thr=0x7f578b1ca980, pc=pc@entry=4904437) at tsan_rtl.cpp:510
29 0x000000000046fcb4 in syscall_pre_fork (pc=1) at tsan_interceptors_posix.cpp:2577
30 0x000000000046fc9b in __sanitizer_syscall_pre_impl_fork () at sanitizer_common_syscalls.inc:3094
31 0x00000000004ad5f5 in myfork () at syscall.h:9
32 main () at fork_deadlock.cpp:46

Depends on D114595.

Reviewed By: melver

Differential Revision: https://reviews.llvm.org/D114597

compiler-rt/lib/tsan/rtl/tsan_rtl.cpp

@@ -506,13 +506,16 @@ void ForkBefore(ThreadState *thr, uptr pc) NO_THREAD_SAFETY_ANALYSIS {
   // On OS X libSystem_atfork_prepare/parent/child callbacks are called
   // after/before our callbacks and they call free.
   thr->ignore_interceptors++;
+  // Disables memory write in OnUserAlloc/Free.
+  thr->ignore_reads_and_writes++;
 
   __tsan_test_only_on_fork();
 }
 
 void ForkParentAfter(ThreadState *thr, uptr pc) NO_THREAD_SAFETY_ANALYSIS {
   thr->suppress_reports--;  // Enabled in ForkBefore.
   thr->ignore_interceptors--;
+  thr->ignore_reads_and_writes--;
   AllocatorUnlock();
   ScopedErrorReportLock::Unlock();
   ctx->report_mtx.Unlock();
@@ -523,6 +526,7 @@ void ForkChildAfter(ThreadState *thr, uptr pc,
                     bool start_thread) NO_THREAD_SAFETY_ANALYSIS {
   thr->suppress_reports--;  // Enabled in ForkBefore.
   thr->ignore_interceptors--;
+  thr->ignore_reads_and_writes--;
   AllocatorUnlock();
   ScopedErrorReportLock::Unlock();
   ctx->report_mtx.Unlock();