tsan: do not deadlock on fork

Currently correct programs can deadlock after fork, because atomic operations and async-signal-safe calls are not async-signal-safe under tsan.
With this change:
- if a single-threaded program forks, the child continues running with verification enabled (the tsan background thread is recreated as well)
- if a multi-threaded program forks, then the child runs with verification disabled (memory accesses, atomic operations and interceptors are disabled); it's expected that it will exec soon anyway
- if the child tries to create more threads after multi-threaded fork, the program aborts with error message
- die_after_fork flag is added that allows to continue running, but all bets are off

http://llvm-reviews.chandlerc.com/D2614

llvm-svn: 199993

1 files changed, 42 insertions, 0 deletions

diff --git a/compiler-rt/lib/tsan/lit_tests/fork_multithreaded.cc b/compiler-rt/lib/tsan/lit_tests/fork_multithreaded.cc
new file mode 100644
index 00000000000..474b53e425a
--- /dev/null
+++ b/compiler-rt/lib/tsan/lit_tests/fork_multithreaded.cc
@@ -0,0 +1,42 @@
+// RUN: %clangxx_tsan -O1 %s -o %t && %t 2>&1 | FileCheck %s -check-prefix=CHECK-DIE
+// RUN: %clangxx_tsan -O1 %s -o %t && TSAN_OPTIONS="die_after_fork=0" %t 2>&1 | FileCheck %s -check-prefix=CHECK-NODIE
+#include <stdlib.h>
+#include <stdio.h>
+#include <errno.h>
+#include <pthread.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+static void *sleeper(void *p) {
+  sleep(10);
+  return 0;
+}
+
+int main() {
+  pthread_t th;
+  pthread_create(&th, 0, sleeper, 0);
+  switch (fork()) {
+  default:  // parent
+    while (wait(0) < 0) {}
+    break;
+  case 0:  // child
+    {
+      pthread_t th2;
+      pthread_create(&th2, 0, sleeper, 0);
+      exit(0);
+      break;
+    }
+  case -1:  // error
+    fprintf(stderr, "failed to fork (%d)\n", errno);
+    exit(1);
+  }
+  fprintf(stderr, "OK\n");
+}
+
+// CHECK-DIE: ThreadSanitizer: starting new threads after muti-threaded fork is not supported
+// CHECK-DIE: OK
+
+// CHECK-NODIE-NOT: ThreadSanitizer: starting new threads after muti-threaded fork is not supported
+// CHECK-NODIE: OK
+