Add support for backgrounding processes on the Mac

base/process/process_mac.cc

+// Copyright 2015 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/process/process.h"
+
+#include "base/mac/mac_util.h"
+#include "base/mac/mach_logging.h"
+
+#include <mach/mach.h>
+
+// The following was added to <mach/task_policy.h> after 10.8.
+#ifndef TASK_OVERRIDE_QOS_POLICY
+
+#define TASK_OVERRIDE_QOS_POLICY 9
+
+typedef struct task_category_policy task_category_policy_data_t;
+typedef struct task_category_policy* task_category_policy_t;
+
+enum task_latency_qos {
+  LATENCY_QOS_TIER_UNSPECIFIED = 0x0,
+  LATENCY_QOS_TIER_0 = ((0xFF << 16) | 1),
+  LATENCY_QOS_TIER_1 = ((0xFF << 16) | 2),
+  LATENCY_QOS_TIER_2 = ((0xFF << 16) | 3),
+  LATENCY_QOS_TIER_3 = ((0xFF << 16) | 4),
+  LATENCY_QOS_TIER_4 = ((0xFF << 16) | 5),
+  LATENCY_QOS_TIER_5 = ((0xFF << 16) | 6)
+};
+typedef integer_t task_latency_qos_t;
+enum task_throughput_qos {
+  THROUGHPUT_QOS_TIER_UNSPECIFIED = 0x0,
+  THROUGHPUT_QOS_TIER_0 = ((0xFE << 16) | 1),
+  THROUGHPUT_QOS_TIER_1 = ((0xFE << 16) | 2),
+  THROUGHPUT_QOS_TIER_2 = ((0xFE << 16) | 3),
+  THROUGHPUT_QOS_TIER_3 = ((0xFE << 16) | 4),
+  THROUGHPUT_QOS_TIER_4 = ((0xFE << 16) | 5),
+  THROUGHPUT_QOS_TIER_5 = ((0xFE << 16) | 6),
+};
+
+#define LATENCY_QOS_LAUNCH_DEFAULT_TIER LATENCY_QOS_TIER_3
+#define THROUGHPUT_QOS_LAUNCH_DEFAULT_TIER THROUGHPUT_QOS_TIER_3
+
+typedef integer_t task_throughput_qos_t;
+
+struct task_qos_policy {
+  task_latency_qos_t task_latency_qos_tier;
+  task_throughput_qos_t task_throughput_qos_tier;
+};
+
+typedef struct task_qos_policy* task_qos_policy_t;
+#define TASK_QOS_POLICY_COUNT \
+  ((mach_msg_type_number_t)(sizeof(struct task_qos_policy) / sizeof(integer_t)))
+
+#endif  // TASK_OVERRIDE_QOS_POLICY
+
+namespace base {
+
+bool Process::CanBackgroundProcesses() {
+  return true;
+}
+
+bool Process::IsProcessBackgrounded(mach_port_t task_port) const {
+  // See SetProcessBackgrounded().
+  DCHECK(IsValid());
+
+  task_category_policy_data_t category_policy;
+  mach_msg_type_number_t task_info_count = TASK_CATEGORY_POLICY_COUNT;
+  boolean_t get_default = FALSE;
+
+  kern_return_t result =
+      task_policy_get(task_port, TASK_CATEGORY_POLICY,
+                      reinterpret_cast<task_policy_t>(&category_policy),
+                      &task_info_count, &get_default);
+  MACH_DCHECK(result == KERN_SUCCESS, result);

[Robert Sesek, 2015/03/13 04:57:01]

It may be more helpful to log this, rather than just DCHECK. Looking at other
base/mac/ and Mach-related code, that seems to be the norm.

Change this to:

MACH_LOG_IF(ERROR, result != KERN_SUCCESS, result) << "task_policy_get
TASK_CATEGORY_POLICY";

[shrike, 2015/03/18 16:20:22]

Thank you. Done.

+
+  if (result == KERN_SUCCESS && get_default == FALSE) {
+    return category_policy.role == TASK_BACKGROUND_APPLICATION;
+  }
+  return false;
+}
+
+bool Process::SetProcessBackgrounded(mach_port_t task_port, bool background) {
+  DCHECK(IsValid());
+
+  if (!CanBackgroundProcesses() || task_port == TASK_NULL) {
+    return false;
+  }
+
+  struct task_category_policy task_category_policy;

[Robert Sesek, 2015/03/13 04:57:01]

This function isn't consistently typed or named with IsProcessBackgrounded(). To
make them consistent, use |task_category_policy| as the type (no |struct |
required, since this is C++), but use the name above (category_poilcy). Use the
same type and name in IsProcessBackgrounded().

[shrike, 2015/03/18 16:20:23]

Done.

+  task_category_policy.role =
+      background ? TASK_BACKGROUND_APPLICATION : TASK_FOREGROUND_APPLICATION;
+  kern_return_t result =
+      task_policy_set(task_port, TASK_CATEGORY_POLICY,
+                      reinterpret_cast<task_policy_t>(&task_category_policy),
+                      TASK_CATEGORY_POLICY_COUNT);
+  MACH_DCHECK(result == KERN_SUCCESS, result);
+
+  if (result != KERN_SUCCESS) {
+    return false;

[Robert Sesek, 2015/03/13 04:57:01]

Here, you could just do:

MACH_LOG(ERROR, result) << "task_policy_set TASK_CATEGORY_POLICY"

[shrike, 2015/03/18 16:20:22]

Done.

+  } else if (!mac::IsOSMavericksOrLater()) {
+    return true;
+  }
+
+  // Latency QoS regulates timer throttling/accuracy. Select default tier
+  // on foreground because precise timer firing isn't needed

[Robert Sesek, 2015/03/13 04:57:01]

nit: punctuation

[shrike, 2015/03/18 16:20:22]

(Not used to ending my comments with punctuation). Done.

+  struct task_qos_policy qosinfo = {

[Robert Sesek, 2015/03/13 04:57:01]

naming: qos_policy

[shrike, 2015/03/18 16:20:23]

Done.

+      background ? LATENCY_QOS_TIER_5 : LATENCY_QOS_LAUNCH_DEFAULT_TIER,
+      background ? THROUGHPUT_QOS_TIER_5 : THROUGHPUT_QOS_LAUNCH_DEFAULT_TIER
+  };
+  result = task_policy_set(task_port, TASK_OVERRIDE_QOS_POLICY,
+                           reinterpret_cast<task_policy_t>(&qosinfo),
+                           TASK_QOS_POLICY_COUNT);
+  MACH_DCHECK(result == KERN_SUCCESS, result);

[Robert Sesek, 2015/03/13 04:57:01]

MACH_LOG_IF as above, or restructure:

if (result != KERN_SUCCESS) {
  MACH_LOG(ERROR, result) << "task_policy_set TASK_OVERRIDE_QOS_POLICY";
  return false;
}

return true;

[shrike, 2015/03/18 16:20:23]

Done.

+
+  return result == KERN_SUCCESS;
+}
+
+}  // namespace base