tsan: add io_sync flag that controls amount of IO synchronization

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@170427 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 24 insertions, 2 deletions

diff --git a/lib/tsan/rtl/tsan_fd.cc b/lib/tsan/rtl/tsan_fd.cc
index 4431097e1..7428596b1 100644
--- a/lib/tsan/rtl/tsan_fd.cc
+++ b/lib/tsan/rtl/tsan_fd.cc
@@ -92,7 +92,15 @@ static void init(ThreadState *thr, uptr pc, int fd, FdSync *s) {
   // See e.g. libc __res_iclose().
   if (d->sync)
     unref(thr, pc, d->sync);
-  d->sync = s;
+  if (flags()->io_sync == 0) {
+    unref(thr, pc, s);
+    d->sync = 0;
+  } else if (flags()->io_sync == 1) {
+    d->sync = s;
+  } else if (flags()->io_sync == 2) {
+    unref(thr, pc, s);
+    d->sync = &fdctx.globsync;
+  }
   d->creation_tid = thr->tid;
   d->creation_stack = CurrentStackId(thr, pc);
   // To catch races between fd usage and open.
@@ -171,8 +179,9 @@ void FdDup(ThreadState *thr, uptr pc, int oldfd, int newfd) {
 void FdPipeCreate(ThreadState *thr, uptr pc, int rfd, int wfd) {
   DPrintf("#%d: FdCreatePipe(%d, %d)\n", thr->tid, rfd, wfd);
   FdSync *s = allocsync();
-  init(thr, pc, rfd, s);
+  init(thr, pc, rfd, ref(s));
   init(thr, pc, wfd, ref(s));
+  unref(thr, pc, s);
 }
 
 void FdEventCreate(ThreadState *thr, uptr pc, int fd) {
diff --git a/lib/tsan/rtl/tsan_flags.cc b/lib/tsan/rtl/tsan_flags.cc
index 25c370f03..88c4bb6a2 100644
--- a/lib/tsan/rtl/tsan_flags.cc
+++ b/lib/tsan/rtl/tsan_flags.cc
@@ -58,6 +58,7 @@ void InitializeFlags(Flags *f, const char *env) {
   f->running_on_valgrind = false;
   f->external_symbolizer_path = "";
   f->history_size = kGoMode ? 1 : 2;  // There are a lot of goroutines in Go.
+  f->io_sync = 1;
 
   // Let a frontend override.
   OverrideFlags(f);
@@ -83,6 +84,7 @@ void InitializeFlags(Flags *f, const char *env) {
   ParseFlag(env, &f->stop_on_start, "stop_on_start");
   ParseFlag(env, &f->external_symbolizer_path, "external_symbolizer_path");
   ParseFlag(env, &f->history_size, "history_size");
+  ParseFlag(env, &f->io_sync, "io_sync");
 
   if (!f->report_bugs) {
     f->report_thread_leaks = false;
@@ -95,6 +97,12 @@ void InitializeFlags(Flags *f, const char *env) {
            " (must be [0..7])\n");
     Die();
   }
+
+  if (f->io_sync < 0 || f->io_sync > 2) {
+    Printf("ThreadSanitizer: incorrect value for io_sync"
+           " (must be [0..2])\n");
+    Die();
+  }
 }
 
 }  // namespace __tsan
diff --git a/lib/tsan/rtl/tsan_flags.h b/lib/tsan/rtl/tsan_flags.h
index 2fdcc2f1b..6547911ec 100644
--- a/lib/tsan/rtl/tsan_flags.h
+++ b/lib/tsan/rtl/tsan_flags.h
@@ -77,6 +77,11 @@ struct Flags {
   // the amount of memory accesses, up to history_size=7 that amounts to
   // 4M memory accesses.  The default value is 2 (128K memory accesses).
   int history_size;
+  // Controls level of synchronization implied by IO operations.
+  // 0 - no synchronization
+  // 1 - reasonable level of synchronization (write->read)
+  // 2 - global synchronization of all IO operations
+  int io_sync;
 };
 
 Flags *flags();