Add ScopedTaskSuspend and its test.

This also introduces ScopedFcntlFlags.

TEST=util_test ScopedTaskSuspend.*:ScopedFcntlFlags.*
R=rsesek@chromium.org

Review URL: https://codereview.chromium.org/649693002

util/mach/scoped_task_suspend.cc

@@ -0,0 +1,39 @@
+// Copyright 2014 The Crashpad Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "util/mach/scoped_task_suspend.h"
+
+#include "base/logging.h"
+#include "base/mac/mach_logging.h"
+
+namespace crashpad {
+
+ScopedTaskSuspend::ScopedTaskSuspend(task_t task) : task_(task) {
+  DCHECK_NE(task_, mach_task_self());
+
+  kern_return_t kr = task_suspend(task_);
+  if (kr != KERN_SUCCESS) {
+    task_ = TASK_NULL;
+    MACH_LOG(ERROR, kr) << "task_suspend";
+  }
+}
+
+ScopedTaskSuspend::~ScopedTaskSuspend() {
+  if (task_ != TASK_NULL) {
+    kern_return_t kr = task_resume(task_);
+    MACH_LOG_IF(ERROR, kr != KERN_SUCCESS, kr) << "task_resume";
+  }
+}
+
+}  // namespace crashpad

util/mach/scoped_task_suspend.h

@@ -0,0 +1,45 @@
+// Copyright 2014 The Crashpad Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef CRASHPAD_UTIL_MACH_SCOPED_TASK_SUSPEND_H_
+#define CRASHPAD_UTIL_MACH_SCOPED_TASK_SUSPEND_H_
+
+#include <mach/mach.h>
+
+#include "base/basictypes.h"
+
+namespace crashpad {
+
+//! \brief Manages the suspension of another task.
+//!
+//! While an object of this class exists, the other task will be suspended. Once
+//! the object is destroyed, the other task will become eligible for resumption.
+//! Note that suspensions are counted, and the task will not actually resume
+//! unless its suspend count drops to 0.
+//!
+//! Callers should not attempt to suspend the current task (`mach_task_self()`).
+class ScopedTaskSuspend {
+ public:
+  explicit ScopedTaskSuspend(task_t task);
+  ~ScopedTaskSuspend();
+
+ private:
+  task_t task_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedTaskSuspend);
+};
+
+}  // namespace crashpad
+
+#endif  // CRASHPAD_UTIL_MACH_SCOPED_TASK_SUSPEND_H_

util/mach/scoped_task_suspend_test.cc

@@ -0,0 +1,87 @@
+// Copyright 2014 The Crashpad Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "util/mach/scoped_task_suspend.h"
+
+#include <mach/mach.h>
+
+#include "gtest/gtest.h"
+#include "util/file/fd_io.h"
+#include "util/test/mac/mach_errors.h"
+#include "util/test/mac/mach_multiprocess.h"
+
+namespace crashpad {
+namespace test {
+namespace {
+
+int SuspendCount(task_t task) {
+  // As of the 10.8 SDK, the preferred routine is MACH_TASK_BASIC_INFO.
+  // TASK_BASIC_INFO_64 is equivalent and works on earlier systems.
+  task_basic_info_64 task_basic_info;
+  mach_msg_type_number_t task_basic_info_count = TASK_BASIC_INFO_64_COUNT;
+  kern_return_t kr = task_info(task,
+                               TASK_BASIC_INFO_64,
+                               reinterpret_cast<task_info_t>(&task_basic_info),
+                               &task_basic_info_count);
+  if (kr != KERN_SUCCESS) {
+    ADD_FAILURE() << MachErrorMessage(kr, "task_info");
+    return -1;
+  }
+
+  return task_basic_info.suspend_count;
+}
+
+class ScopedTaskSuspendTest final : public MachMultiprocess {
+ public:
+  ScopedTaskSuspendTest() : MachMultiprocess() {}
+  ~ScopedTaskSuspendTest() {}
+
+ private:
+  // MachMultiprocess:
+
+  virtual void MachMultiprocessParent() override {
+    task_t child_task = ChildTask();
+
+    EXPECT_EQ(0, SuspendCount(child_task));
+
+    {
+      ScopedTaskSuspend suspend(child_task);
+      EXPECT_EQ(1, SuspendCount(child_task));
+
+      {
+        ScopedTaskSuspend suspend_again(child_task);
+        EXPECT_EQ(2, SuspendCount(child_task));
+      }
+
+      EXPECT_EQ(1, SuspendCount(child_task));
+    }
+
+    EXPECT_EQ(0, SuspendCount(child_task));
+  }
+
+  virtual void MachMultiprocessChild() override {
+    CheckedReadFDAtEOF(ReadPipeFD());
+  }
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedTaskSuspendTest);
+};
+
+TEST(ScopedTaskSuspend, ScopedTaskSuspend) {
+  ScopedTaskSuspendTest scoped_task_suspend_test;
+  scoped_task_suspend_test.Run();
+}
+
+}  // namespace
+}  // namespace test
+}  // namespace crashpad

util/util.gyp

@@ -71,6 +71,8 @@
         'mach/mach_extensions.h',
         'mach/mach_message_server.cc',
         'mach/mach_message_server.h',
+        'mach/scoped_task_suspend.cc',
+        'mach/scoped_task_suspend.h',
         'mach/symbolic_constants_mach.cc',
         'mach/symbolic_constants_mach.h',
         'mach/task_memory.cc',
@@ -225,6 +227,7 @@
         'mach/exception_ports_test.cc',
         'mach/mach_extensions_test.cc',
         'mach/mach_message_server_test.cc',
+        'mach/scoped_task_suspend_test.cc',
         'mach/symbolic_constants_mach_test.cc',
         'mach/task_memory_test.cc',
         'misc/clock_test.cc',