From 5d9f6da6541c24077f236fe9a1837e0e8261a3ea Mon Sep 17 00:00:00 2001
From: ulan <ulan@chromium.org>
Date: Mon, 9 May 2016 04:55:14 -0700
Subject: [PATCH] Instrument callers of Semaphore::Signal to help with
 investigation of flaky crashes.

BUG=chromium:609249
LOG=NO

Review-Url: https://codereview.chromium.org/1961893002
Cr-Commit-Position: refs/heads/master@{#36106}
---
 src/base/platform/semaphore.cc | 14 +++++++-------
 src/base/platform/semaphore.h  |  3 ++-
 src/debug/debug.cc             |  2 +-
 src/heap/mark-compact.cc       |  4 ++--
 src/heap/page-parallel-job.h   |  2 +-
 src/heap/spaces.cc             |  3 ++-
 src/log.cc                     |  2 +-
 7 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/src/base/platform/semaphore.cc b/src/base/platform/semaphore.cc
index c94bfa7953..64489f91c2 100644
--- a/src/base/platform/semaphore.cc
+++ b/src/base/platform/semaphore.cc
@@ -34,11 +34,11 @@ Semaphore::~Semaphore() {
   USE(result);
 }
 
-
-void Semaphore::Signal() {
+void Semaphore::Signal(const char* caller) {
   kern_return_t result = semaphore_signal(native_handle_);
   DCHECK_EQ(KERN_SUCCESS, result);
   USE(result);
+  USE(caller);
 }
 
 
@@ -104,11 +104,11 @@ Semaphore::~Semaphore() {
   USE(result);
 }
 
-
-void Semaphore::Signal() {
+void Semaphore::Signal(const char* caller) {
   int result = sem_post(&native_handle_);
   if (result != 0) {
-    V8_Fatal(__FILE__, __LINE__, "Semaphore signal failure: %d\n", errno);
+    V8_Fatal(__FILE__, __LINE__,
+             "Semaphore signal failure: %d called by '%s'\n", errno, caller);
   }
 }
 
@@ -177,12 +177,12 @@ Semaphore::~Semaphore() {
   USE(result);
 }
 
-
-void Semaphore::Signal() {
+void Semaphore::Signal(const char* caller) {
   LONG dummy;
   BOOL result = ReleaseSemaphore(native_handle_, 1, &dummy);
   DCHECK(result);
   USE(result);
+  USE(caller);
 }
 
 
diff --git a/src/base/platform/semaphore.h b/src/base/platform/semaphore.h
index 18700d1ba0..ad8c7ec68b 100644
--- a/src/base/platform/semaphore.h
+++ b/src/base/platform/semaphore.h
@@ -37,7 +37,8 @@ class Semaphore final {
   ~Semaphore();
 
   // Increments the semaphore counter.
-  void Signal();
+  // TODO(ulan): remove caller parameter once crbug.com/609249 is fixed.
+  void Signal(const char* caller = nullptr);
 
   // Suspends the calling thread until the semaphore counter is non zero
   // and then decrements the semaphore counter.
diff --git a/src/debug/debug.cc b/src/debug/debug.cc
index 3b5fb5f53d..7272ee6731 100644
--- a/src/debug/debug.cc
+++ b/src/debug/debug.cc
@@ -2159,7 +2159,7 @@ void Debug::EnqueueCommandMessage(Vector<const uint16_t> command,
       client_data);
   isolate_->logger()->DebugTag("Put command on command_queue.");
   command_queue_.Put(message);
-  command_received_.Signal();
+  command_received_.Signal("Debug::EnqueueCommandMessage");
 
   // Set the debug command break flag to have the command processed.
   if (!in_debug_scope()) isolate_->stack_guard()->RequestDebugCommand();
diff --git a/src/heap/mark-compact.cc b/src/heap/mark-compact.cc
index 89ca782c26..ad0c58e4a8 100644
--- a/src/heap/mark-compact.cc
+++ b/src/heap/mark-compact.cc
@@ -480,7 +480,7 @@ class MarkCompactCollector::Sweeper::SweeperTask : public v8::Task {
       DCHECK_LE(space_id, LAST_PAGED_SPACE);
       sweeper_->ParallelSweepSpace(static_cast<AllocationSpace>(space_id), 0);
     }
-    pending_sweeper_tasks_->Signal();
+    pending_sweeper_tasks_->Signal("SweeperTask::Run");
   }
 
   Sweeper* sweeper_;
@@ -585,7 +585,7 @@ bool MarkCompactCollector::Sweeper::IsSweepingCompleted() {
           base::TimeDelta::FromSeconds(0))) {
     return false;
   }
-  pending_sweeper_tasks_semaphore_.Signal();
+  pending_sweeper_tasks_semaphore_.Signal("Sweeper::IsSweepingCompleted");
   return true;
 }
 
diff --git a/src/heap/page-parallel-job.h b/src/heap/page-parallel-job.h
index 720e288fc8..4fde2bdb8a 100644
--- a/src/heap/page-parallel-job.h
+++ b/src/heap/page-parallel-job.h
@@ -161,7 +161,7 @@ class PageParallelJob {
           current = items_;
         }
       }
-      on_finish_->Signal();
+      on_finish_->Signal("PageParallelJob::Task::RunInternal");
     }
 
     Heap* heap_;
diff --git a/src/heap/spaces.cc b/src/heap/spaces.cc
index 7cfa4c2949..1ab5de7379 100644
--- a/src/heap/spaces.cc
+++ b/src/heap/spaces.cc
@@ -356,7 +356,8 @@ class MemoryAllocator::Unmapper::UnmapFreeMemoryTask : public v8::Task {
   // v8::Task overrides.
   void Run() override {
     unmapper_->PerformFreeMemoryOnQueuedChunks();
-    unmapper_->pending_unmapping_tasks_semaphore_.Signal();
+    unmapper_->pending_unmapping_tasks_semaphore_.Signal(
+        "Unmapper::UnmapFreeMemoryTask::Run");
   }
 
   Unmapper* unmapper_;
diff --git a/src/log.cc b/src/log.cc
index 416204143b..a3557bfb19 100644
--- a/src/log.cc
+++ b/src/log.cc
@@ -561,7 +561,7 @@ class Profiler: public base::Thread {
     } else {
       buffer_[head_] = *sample;
       head_ = Succ(head_);
-      buffer_semaphore_.Signal();  // Tell we have an element.
+      buffer_semaphore_.Signal("Profiler::Insert");  // Tell we have an element.
     }
   }