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..7a4b8ffdea646c2f1401021d59e61889588af5d4 100644
--- a/base/threading/platform_thread_linux.cc
+++ b/base/threading/platform_thread_linux.cc
@@ -76,6 +76,24 @@ 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;
+
+    if (pthread_setschedparam(pthread_self(), SCHED_RR, &sched_param) == 0) {

[DaleCurtis, 2013/05/28 19:15:25]

int res = pthread_setschedparam(pthread_self(), SCHED_RR, &sched_param);
(D)LOG_IF(INFO, res != 0) << "Failed to set audio thread to real time";
#if defined(OS_CHROMEOS)
CHECK_EQ(res, 0);
#endif

Instead?

[dgreid, 2013/05/28 20:29:42]

There still needs to be a return in the success path, but keeping res around for
the check seems like a good idea, I'll modify it accordingly.
This will fail on ChromeOS versions that don't have the permission set (older
ones).  That could cause some trouble when bisecting, I've added a DCHECK, and
can make it a CHECK if the consensus is that it is worth it.

+      // Got real time priority, no need to set nice level.
+      return;
+    } else {
+      LOG(INFO) << "Failed to set audio thread to real time";
+#if defined(OS_CHROMEOS)
+      return;  // This should always work on ChromeOS, return on error.
+#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