[tsan] Test __tsan_test_only_on_fork only on Mac

[vitalybuka]

According to https://reviews.llvm.org/D114250
this was to handle Mac specific issue, however
the test is Linux only.

The test effectively prevents to lock main allocator
on fork, but we do that on Linux for other
sanitizers for years, and need to do the same
for TSAN to avoid deadlocks.

[llvmbot]

@llvm/pr-subscribers-compiler-rt-sanitizer

Author: Vitaly Buka (vitalybuka)

Changes

According to https://reviews.llvm.org/D114250
this was to handle Mac specific issue, however
the test is Linux only.

The test effectively prevents to lock main allocator
on fork, but we do that on Linux for other
sanitizers for years, and need to do the same
for TSAN to avoid deadlocks.

---

Full diff: https://github.com/llvm/llvm-project/pull/96597.diff

2 Files Affected:

• (modified) compiler-rt/lib/tsan/rtl/tsan_rtl.cpp (+4)
• (renamed) compiler-rt/test/tsan/Darwin/fork_deadlock.cpp ()

diff --git a/compiler-rt/lib/tsan/rtl/tsan_rtl.cpp b/compiler-rt/lib/tsan/rtl/tsan_rtl.cpp
index fd9441dfcb53c..2d5992b703a6a 100644
--- a/compiler-rt/lib/tsan/rtl/tsan_rtl.cpp
+++ b/compiler-rt/lib/tsan/rtl/tsan_rtl.cpp
@@ -35,8 +35,10 @@ extern "C" void __tsan_resume() {
   __tsan_resumed = 1;
 }
 
+#if SANITIZER_APPLE
 SANITIZER_WEAK_DEFAULT_IMPL
 void __tsan_test_only_on_fork() {}
+#endif
 
 namespace __tsan {
 
@@ -828,7 +830,9 @@ void ForkBefore(ThreadState* thr, uptr pc) SANITIZER_NO_THREAD_SAFETY_ANALYSIS {
   // Disables memory write in OnUserAlloc/Free.
   thr->ignore_reads_and_writes++;
 
+#  if SANITIZER_APPLE
   __tsan_test_only_on_fork();
+#  endif
 }
 
 static void ForkAfter(ThreadState* thr) SANITIZER_NO_THREAD_SAFETY_ANALYSIS {
diff --git a/compiler-rt/test/tsan/Linux/fork_deadlock.cpp b/compiler-rt/test/tsan/Darwin/fork_deadlock.cpp
similarity index 100%
rename from compiler-rt/test/tsan/Linux/fork_deadlock.cpp
rename to compiler-rt/test/tsan/Darwin/fork_deadlock.cpp

[vitalybuka]

I am going to land dependent changes on top of this patch.

If this breaks stuff on some Apple bots, instead of reverting, please just mark the test as UNSUPPORTED, and let me know.

[aeubanks]

we're seeing the following on our mac bots:

 /Volumes/Work/s/w/ir/cache/builder/src/third_party/llvm/compiler-rt/test/tsan/Darwin/fork_deadlock.cpp:8:10: fatal error: 'syscall.h' file not found
     8 | #include "syscall.h"
       |          ^~~~~~~~~~~
 1 error generated.

and yeah I don't see a syscall.h in compiler-rt/test/tsan/Darwin/syscall.h, only compiler-rt/test/tsan/Linux/syscall.h

[aeubanks]

test marked UNSUPPORTED in 8044158