[tsan] Fix fork() and fork-based tests for OS X

[kubamracek]

Summary

On OS X, fork() under TSan asserts (in debug builds only) because REAL(fork) calls some intercepted functions, which check that no internal locks are held via CheckNoLocks(). But the wrapper of fork intentionally holds some locks. The assert backtrace:

FATAL: ThreadSanitizer CHECK failed: .../llvm/projects/compiler-rt/lib/tsan/rtl/tsan_mutex.cc:169 "((locked_[i])) == ((0))" (0x224, 0x0)
frame #6: 0x00000001000b3df1 libclang_rt.tsan_osx_dynamic.dylib`__tsan::TsanCheckFailed(file=".../llvm/projects/compiler-rt/lib/tsan/rtl/tsan_mutex.cc", line=169, cond="((locked_[i])) == ((0))", v1=548, v2=0) + 97 at tsan_rtl_report.cc:45
frame #7: 0x0000000100009289 libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::CheckFailed(file=".../llvm/projects/compiler-rt/lib/tsan/rtl/tsan_mutex.cc", line=169, cond="((locked_[i])) == ((0))", v1=548, v2=0) + 73 at sanitizer_common.cc:159
frame #8: 0x000000010008158c libclang_rt.tsan_osx_dynamic.dylib`__tsan::InternalDeadlockDetector::CheckNoLocks(this=0x00000001010465b8) + 140 at tsan_mutex.cc:169
frame #9: 0x00000001000815c5 libclang_rt.tsan_osx_dynamic.dylib`__tsan::CheckNoLocks(thr=0x0000000100ffe000) + 21 at tsan_mutex.cc:176
frame #10: 0x000000010003d55e libclang_rt.tsan_osx_dynamic.dylib`__tsan::ScopedInterceptor::~ScopedInterceptor(this=0x00007fff5fbff838) + 174 at tsan_interceptors.cc:302
frame #11: 0x000000010003d7fe libclang_rt.tsan_osx_dynamic.dylib`__tsan::ScopedInterceptor::~ScopedInterceptor(this=0x00007fff5fbff838) + 14 at tsan_interceptors.cc:291
frame #12: 0x00000001000bfcaf libclang_rt.tsan_osx_dynamic.dylib`::wrap_OSSpinLockLock(lock=0x0000000100ffd5ac) + 335 at tsan_interceptors_mac.cc:33
frame #13: 0x00007fff99dd6d7d libsystem_pthread.dylib`_pthread_fork_prepare + 43
frame #14: 0x00007fff9a4c7a74 libSystem.B.dylib`libSystem_atfork_prepare + 24
frame #15: 0x00007fff9f21af9c libsystem_c.dylib`fork + 12
frame #16: 0x0000000100043e5d libclang_rt.tsan_osx_dynamic.dylib`::wrap_fork(fake=17065400) + 125 at tsan_interceptors.cc:2171
frame #17: 0x0000000100000d98 fork_atexit.cc.tmp`main + 40 at fork_atexit.cc:20 [opt]
frame #18: 0x00007fff9c4875ad libdyld.dylib`start + 1

This patch fixes that by using ScopedIgnoreInterceptors during the call to REAL(fork). After that, all the fork-based tests seem to pass on OS X, so let's just remove all the UNSUPPORTED: darwin annotations we have.

[dvyukov]

LGTM with a nit

lib/tsan/rtl/tsan_interceptors.cc

2173

Please add a comment here explaining why we do this.

lib/tsan/rtl/tsan_interceptors.cc

TSAN_INTERCEPTOR(int, getaddrinfo, void *node, void *service,
   return res;
 }
 
 TSAN_INTERCEPTOR(int, fork, int fake) {
   if (cur_thread()->in_symbolizer)
     return REAL(fork)(fake);
   SCOPED_INTERCEPTOR_RAW(fork, fake);
   ForkBefore(thr, pc);
-  int pid = REAL(fork)(fake);
+  int pid;
+  {
+    ScopedIgnoreInterceptors ignore;
+    pid = REAL(fork)(fake);
+  }
   if (pid == 0) {
     // child
     ForkChildAfter(thr, pc);
     FdOnFork(thr, pc);
   } else if (pid > 0) {
     // parent
     ForkParentAfter(thr, pc);
   } else {

test/tsan/fork_atexit.cc

 // RUN: %clangxx_tsan -O1 %s -o %t && %env_tsan_opts=atexit_sleep_ms=50 %run %t 2>&1 | FileCheck %s
-// UNSUPPORTED: darwin
 #include <pthread.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 
 void foo() {

test/tsan/fork_deadlock.cc

 // RUN: %clangxx_tsan -O1 %s -o %t && %env_tsan_opts=atexit_sleep_ms=50 %run %t 2>&1 | FileCheck %s
-// UNSUPPORTED: darwin
 #include "test.h"
 #include <errno.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 
 int counter;
 
 static void *incrementer(void *p) {

test/tsan/fork_multithreaded.cc

 // RUN: %clangxx_tsan -O1 %s -o %t && %run %t 2>&1 | FileCheck %s -check-prefix=CHECK-DIE
 // RUN: %clangxx_tsan -O1 %s -o %t && %env_tsan_opts=die_after_fork=0 %run %t 2>&1 | FileCheck %s -check-prefix=CHECK-NODIE
-// UNSUPPORTED: darwin
 #include "test.h"
 #include <errno.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 
 static void *sleeper(void *p) {
   sleep(10);  // not intended to exit during test
   return 0;

test/tsan/fork_multithreaded3.cc

 // RUN: %clangxx_tsan -O1 %s -o %t && %run %t 2>&1 | FileCheck %s
-// UNSUPPORTED: darwin
 #include <stdlib.h>
 #include <stdio.h>
 #include <errno.h>
 #include <pthread.h>
 #include <unistd.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 

test/tsan/vfork.cc

 // RUN: %clangxx_tsan -O1 %s -o %t && %run %t 2>&1 | FileCheck %s
-// UNSUPPORTED: darwin
 #include <pthread.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <sys/types.h>
 
 int fds[2];
 int X;