Add a systrace support for lock contention logging.

- Now several ART executables like oatdump need to link with libcutils
  as the mutex code is shared among them.
- The blocking thread ID and lock owner thread ID are passed to
  ScopedContentionRecorder in the correct order.

Bug: 9986464
Change-Id: Id766de23fbc4af1d8ba2de051595e365b04f5ae7

2 files changed, 12 insertions, 3 deletions

diff --git a/runtime/base/mutex-inl.h b/runtime/base/mutex-inl.h
index 7f3b459..a559d63 100644
--- a/runtime/base/mutex-inl.h
+++ b/runtime/base/mutex-inl.h
@@ -19,7 +19,10 @@
 
 #include "mutex.h"
 
+#define ATRACE_TAG ATRACE_TAG_DALVIK
+
 #include "cutils/atomic-inline.h"
+#include "cutils/trace.h"
 #include "runtime.h"
 #include "thread.h"
 
@@ -45,10 +48,16 @@ class ScopedContentionRecorder {
         blocked_tid_(kLogLockContentions ? blocked_tid : 0),
         owner_tid_(kLogLockContentions ? owner_tid : 0),
         start_nano_time_(kLogLockContentions ? NanoTime() : 0) {
+    if (kLogLockContentions) {
+      std::string msg = StringPrintf("Lock contention on %s (owner tid: %llu)",
+                                     mutex->GetName(), owner_tid);
+      ATRACE_BEGIN(msg.c_str());
+    }
   }
 
   ~ScopedContentionRecorder() {
     if (kLogLockContentions) {
+      ATRACE_END();
       uint64_t end_nano_time = NanoTime();
       mutex_->RecordContention(blocked_tid_, owner_tid_, end_nano_time - start_nano_time_);
     }
diff --git a/runtime/base/mutex.cc b/runtime/base/mutex.cc
index 3007978..b99e7c9 100644
--- a/runtime/base/mutex.cc
+++ b/runtime/base/mutex.cc
@@ -351,7 +351,7 @@ void Mutex::ExclusiveLock(Thread* self) {
         done = android_atomic_acquire_cas(0, 1, &state_) == 0;
       } else {
         // Failed to acquire, hang up.
-        ScopedContentionRecorder scr(this, GetExclusiveOwnerTid(), SafeGetTid(self));
+        ScopedContentionRecorder scr(this, SafeGetTid(self), GetExclusiveOwnerTid());
         android_atomic_inc(&num_contenders_);
         if (futex(&state_, FUTEX_WAIT, 1, NULL, NULL, 0) != 0) {
           // EAGAIN and EINTR both indicate a spurious failure, try again from the beginning.
@@ -554,7 +554,7 @@ void ReaderWriterMutex::ExclusiveLock(Thread* self) {
       done = android_atomic_acquire_cas(0, -1, &state_) == 0;
     } else {
       // Failed to acquire, hang up.
-      ScopedContentionRecorder scr(this, GetExclusiveOwnerTid(), SafeGetTid(self));
+      ScopedContentionRecorder scr(this, SafeGetTid(self), GetExclusiveOwnerTid());
       android_atomic_inc(&num_pending_writers_);
       if (futex(&state_, FUTEX_WAIT, cur_state, NULL, NULL, 0) != 0) {
         // EAGAIN and EINTR both indicate a spurious failure, try again from the beginning.
@@ -623,7 +623,7 @@ bool ReaderWriterMutex::ExclusiveLockWithTimeout(Thread* self, int64_t ms, int32
       if (ComputeRelativeTimeSpec(&rel_ts, end_abs_ts, now_abs_ts)) {
         return false;  // Timed out.
       }
-      ScopedContentionRecorder scr(this, GetExclusiveOwnerTid(), SafeGetTid(self));
+      ScopedContentionRecorder scr(this, SafeGetTid(self), GetExclusiveOwnerTid());
       android_atomic_inc(&num_pending_writers_);
       if (futex(&state_, FUTEX_WAIT, cur_state, &rel_ts, NULL, 0) != 0) {
         if (errno == ETIMEDOUT) {