posix thread: Attempt to set audio threads to real time.

base/threading/platform_thread_linux.cc

Index: base/threading/platform_thread_linux.cc
diff --git a/base/threading/platform_thread_linux.cc b/base/threading/platform_thread_linux.cc
index 42e12c71a554920d94c23c503ff02c80bf8aaad4..6208131d735938844f31c9cb2679a70f59c0818f 100644
--- a/base/threading/platform_thread_linux.cc
+++ b/base/threading/platform_thread_linux.cc
@@ -76,6 +76,25 @@ void PlatformThread::SetName(const char* name) {
 void PlatformThread::SetThreadPriority(PlatformThreadHandle handle,
                                        ThreadPriority priority) {
 #ifndef OS_NACL
+  if (priority == kThreadPriority_RealtimeAudio) {
+    const int kRealTimePrio = 8;
+
+    struct sched_param sched_param;
+    memset(&sched_param, 0, sizeof(sched_param));
+    sched_param.sched_priority = kRealTimePrio;
+
+    int res = pthread_setschedparam(pthread_self(), SCHED_RR, &sched_param);
+    if (res == 0)
+      // Got real time priority, no need to set nice level.
+      return;

[piman, 2013/05/28 21:58:56]

nit: need braces if the clause takes multiple lines.

[dgreid, 2013/05/28 22:18:53]

Done.

+    else
+      LOG(INFO) << "Failed to set audio thread to real time.";
+
+#if defined(OS_CHROMEOS)
+    DCHECK_EQ(res, 0);  // RT prio should always work on ChromeOS.

[piman, 2013/05/28 21:58:56]

This prevents debugging chromeos=1 builds on the desktop.
We're already logging if it fails, that's enough IMO.

[dgreid, 2013/05/28 22:18:53]

Good point, switched this back to a return.

+#endif
+  }
+
   // setpriority(2) will set a thread's priority if it is passed a tid as
   // the 'process identifier', not affecting the rest of the threads in the
   // process. Setting this priority will only succeed if the user has been