Thread priority sticked to REALTIME_AUDIO on Linux

base/threading/platform_thread_linux.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/threading/platform_thread.h"
 
 #include <errno.h>
 #include <sched.h>
 
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/threading/platform_thread_internal_posix.h"
 #include "base/threading/thread_id_name_manager.h"
 #include "base/tracked_objects.h"
 
 #if !defined(OS_NACL)
 #include <pthread.h>
 #include <sys/prctl.h>
 #include <sys/types.h>
 #include <unistd.h>
 #endif
 
 namespace base {
 
 namespace internal {
 
 namespace {
 #if !defined(OS_NACL)
 const struct sched_param kRealTimePrio = {8};
+const struct sched_param kResetPrio = {0};
 #endif
 }  // namespace
 
 const ThreadPriorityToNiceValuePair kThreadPriorityToNiceValueMap[4] = {
     {ThreadPriority::BACKGROUND, 10},
     {ThreadPriority::NORMAL, 0},
     {ThreadPriority::DISPLAY, -6},
     {ThreadPriority::REALTIME_AUDIO, -10},
 };
 
 bool SetThreadPriorityForPlatform(PlatformThreadHandle handle,
                                   ThreadPriority priority) {
 #if !defined(OS_NACL)
+  ThreadPriority current_priority;
+  if (priority != ThreadPriority::REALTIME_AUDIO &&
+      GetThreadPriorityForPlatform(handle, &current_priority) &&
+      current_priority == ThreadPriority::REALTIME_AUDIO) {
+    // If the pthread's round-robin scheduler is already enabled, and the new
+    // priority will use setpriority() instead, the pthread scheduler should be
+    // reset to use SCHED_OTHER so that setpriority() just works.
+    pthread_setschedparam(pthread_self(), SCHED_OTHER, &kResetPrio);
+    return false;
+  }
   // TODO(gab): Assess the correctness of using |pthread_self()| below instead
   // of |handle|. http://crbug.com/468793.
   return priority == ThreadPriority::REALTIME_AUDIO  &&
          pthread_setschedparam(pthread_self(), SCHED_RR, &kRealTimePrio) == 0;
 #else
   return false;
 #endif
 }
 
 bool GetThreadPriorityForPlatform(PlatformThreadHandle handle,
@@ skipping 51 matching lines @@
 #if !defined(THREAD_SANITIZER)
   return 0;
 #else
   // ThreadSanitizer bloats the stack heavily. Evidence has been that the
   // default stack size isn't enough for some browser tests.
   return 2 * (1 << 23);  // 2 times 8192K (the default stack size on Linux).
 #endif
 }
 
 }  // namespace base