Don't DCHECK thread_policy_set() calls because they can fail during runtime

base/threading/platform_thread_mac.mm

 // Copyright (c) 2011 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"
 
 #import <Foundation/Foundation.h>
 #include <dlfcn.h>
 #include <mach/mach.h>
 #include <mach/mach_time.h>
@@ skipping 50 matching lines @@
 
 // static
 const char* PlatformThread::GetName() {
   return current_thread_name.Get();
 }
 
 namespace {
 
 void SetPriorityNormal(mach_port_t mach_thread_id) {
   // Make thread standard policy.
+  // Please note that this call could fail in rare cases depending
+  // on runtime conditions.
   thread_standard_policy policy;
   kern_return_t result = thread_policy_set(mach_thread_id,
                                            THREAD_STANDARD_POLICY,
                                            (thread_policy_t)&policy,
                                            THREAD_STANDARD_POLICY_COUNT);
 
-  DCHECK_EQ(KERN_SUCCESS, result);
+  if (result != KERN_SUCCESS)
+    VLOG(1) << "thread_policy_set() failure: " << result;
 }
 
 // Enables time-contraint policy and priority suitable for low-latency,
 // glitch-resistant audio.
 void SetPriorityRealtimeAudio(mach_port_t mach_thread_id) {
   kern_return_t result;
 
   // Increase thread priority to real-time.
 
+  // Please note that the thread_policy_set() calls may fail in
+  // rare cases if the kernel decides the system is under heavy load
+  // and is unable to handle boosting the thread priority.
+  // In these cases we just return early and go on with life.
+
   // Make thread fixed priority.
   thread_extended_policy_data_t policy;
   policy.timeshare = 0;  // Set to 1 for a non-fixed thread.
   result = thread_policy_set(mach_thread_id,
                              THREAD_EXTENDED_POLICY,
                              (thread_policy_t)&policy,
                              THREAD_EXTENDED_POLICY_COUNT);
-
-  DCHECK_EQ(KERN_SUCCESS, result);
+  if (result != KERN_SUCCESS) {
+    VLOG(1) << "thread_policy_set() failure: " << result;
+    return;
+  }
 
   // Set to relatively high priority.
   thread_precedence_policy_data_t precedence;
   precedence.importance = 63;
   result = thread_policy_set(mach_thread_id,
                              THREAD_PRECEDENCE_POLICY,
                              (thread_policy_t)&precedence,
                              THREAD_PRECEDENCE_POLICY_COUNT);
-  DCHECK_EQ(KERN_SUCCESS, result);
+  if (result != KERN_SUCCESS) {
+    VLOG(1) << "thread_policy_set() failure: " << result;
+    return;
+  }
 
   // Most important, set real-time constraints.
 
   // Define the guaranteed and max fraction of time for the audio thread.
   // These "duty cycle" values can range from 0 to 1.  A value of 0.5
   // means the scheduler would give half the time to the thread.
   // These values have empirically been found to yield good behavior.
   // Good means that audio performance is high and other threads won't starve.
   const double kGuaranteedAudioDutyCycle = 0.75;
   const double kMaxAudioDutyCycle = 0.85;
@@ skipping 20 matching lines @@
   thread_time_constraint_policy_data_t time_constraints;
   time_constraints.period = kTimeQuantum * ms_to_abs_time;
   time_constraints.computation = kAudioTimeNeeded * ms_to_abs_time;
   time_constraints.constraint = kMaxTimeAllowed * ms_to_abs_time;
   time_constraints.preemptible = 0;
 
   result = thread_policy_set(mach_thread_id,
                              THREAD_TIME_CONSTRAINT_POLICY,
                              (thread_policy_t)&time_constraints,
                              THREAD_TIME_CONSTRAINT_POLICY_COUNT);
-  DCHECK_EQ(KERN_SUCCESS, result);
+  if (result != KERN_SUCCESS)
+    VLOG(1) << "thread_policy_set() failure: " << result;
+
+  return;
 }
 
 }  // anonymous namespace
 
 // static
 void PlatformThread::SetThreadPriority(PlatformThreadHandle handle,
                                        ThreadPriority priority) {
   // Convert from pthread_t to mach thread identifier.
   mach_port_t mach_thread_id = pthread_mach_thread_np(handle);
 
   switch (priority) {
     case kThreadPriority_Normal:
       SetPriorityNormal(mach_thread_id);
       break;
     case kThreadPriority_RealtimeAudio:
       SetPriorityRealtimeAudio(mach_thread_id);
       break;
   }
 }
 
 }  // namespace base