Move OomKillsMonitor from a single-threaded SequencedWorkerPool to a non-joinable thread.

components/arc/metrics/oom_kills_monitor.cc

Index: components/arc/metrics/oom_kills_monitor.cc
diff --git a/components/arc/metrics/oom_kills_monitor.cc b/components/arc/metrics/oom_kills_monitor.cc
index 3dc4de62ae9e4f2c07cf35a23871c1267ed2ee41..60e4062d1c31b29cdbe59eaa71b176841dad5ada 100644
--- a/components/arc/metrics/oom_kills_monitor.cc
+++ b/components/arc/metrics/oom_kills_monitor.cc
@@ -33,27 +33,11 @@ using base::StringPiece;
 using base::SequencedWorkerPool;
 using base::TimeDelta;
 
-OomKillsMonitor::OomKillsMonitor()
-    : worker_pool_(
-          new SequencedWorkerPool(1, "oom_kills_monitor")) {}
-
-OomKillsMonitor::~OomKillsMonitor() {
-  Stop();
-}
-
-void OomKillsMonitor::Start() {
-  auto task_runner = worker_pool_->GetTaskRunnerWithShutdownBehavior(
-      SequencedWorkerPool::CONTINUE_ON_SHUTDOWN);
-  task_runner->PostTask(
-      FROM_HERE, base::Bind(&OomKillsMonitor::Run, worker_pool_));
-}
-
-void OomKillsMonitor::Stop() {
-  worker_pool_->Shutdown();
-}
-
 namespace {
 
+base::LazyInstance<OomKillsMonitor>::Leaky g_instance =
+    LAZY_INSTANCE_INITIALIZER;
+
 int64_t GetTimestamp(const StringPiece& line) {
   std::vector<StringPiece> fields = base::SplitStringPiece(
       line, ",", base::TRIM_WHITESPACE, base::SPLIT_WANT_ALL);
@@ -154,9 +138,28 @@ void LogLowMemoryKill(const StringPiece& line) {
 
 }  // namespace
 
+OomKillsMonitor::OomKillsMonitorHandle::OomKillsMonitorHandle(
+    OomKillsMonitor* outer) : outer_(outer) { DCHECK(outer_); }
+
+OomKillsMonitor::OomKillsMonitorHandle::~OomKillsMonitorHandle() {
+  outer_->is_shutting_down_.Set();
+}
+
+OomKillsMonitor::OomKillsMonitor()
+    : worker_thread_("oom_kills_monitor") {}
+
 // static
-void OomKillsMonitor::Run(
-    scoped_refptr<base::SequencedWorkerPool> worker_pool) {
+void OomKillsMonitor::StartMonitoring() {
+  OomKillsMonitor* instance = g_instance.Pointer();
+
+  DCHECK(!instance->IsRunning());
+
+  base::Thread::Options thread_options;
+  thread_options.joinable = false;
+  instance->StartWithOptions(thread_options);
+}

[Luis Héctor Chávez, 2016/08/01 15:48:14]

return OomKillsMonitorHandle(instance); ?

[gab, 2016/08/04 22:42:36]

Yea I was trying to do this on my Windows machine... clearly a failure looking
at the bots. Sprung up my CrOS build on Linux now :-)

+
+void OomKillsMonitor::Run() {
   base::ScopedFILE kmsg_handle(
       base::OpenFile(base::FilePath("/dev/kmsg"), "r"));
   if (!kmsg_handle) {
@@ -171,7 +174,7 @@ void OomKillsMonitor::Run(
   char buf[kMaxBufSize];
 
   while (fgets(buf, kMaxBufSize, kmsg_handle.get())) {
-    if (worker_pool->IsShutdownInProgress()) {
+    if (is_shutting_down_.IsSet()) {
       DVLOG(1) << "Chrome is shutting down, exit now.";
       break;
     }