Add Semaphore and its test, and use it where semaphores are needed.

TEST=util_test Semaphore.*:ProcessReader.*:ExceptionPorts.*
R=rsesek@chromium.org

Review URL: https://codereview.chromium.org/589243003

util/mac/process_reader_test.cc

@@ -14,7 +14,6 @@
 
 #include "util/mac/process_reader.h"
 
-#include <dispatch/dispatch.h>
 #include <mach-o/dyld.h>
 #include <mach-o/dyld_images.h>
 #include <mach/mach.h>
@@ -35,6 +34,7 @@
 #include "util/mac/mach_o_image_reader.h"
 #include "util/mach/mach_extensions.h"
 #include "util/stdlib/pointer_container.h"
+#include "util/synchronization/semaphore.h"
 #include "util/test/errors.h"
 #include "util/test/mac/dyld.h"
 #include "util/test/mac/mach_errors.h"
@@ -170,8 +170,8 @@ class TestThreadPool {
       }
     }
 
-    for (const ThreadInfo* thread_info : thread_infos_) {
-      dispatch_semaphore_signal(thread_info->exit_semaphore);
+    for (ThreadInfo* thread_info : thread_infos_) {
+      thread_info->exit_semaphore.Signal();
     }
 
     for (const ThreadInfo* thread_info : thread_infos_) {
@@ -197,10 +197,8 @@ class TestThreadPool {
       ASSERT_EQ(0, rv);
     }
 
-    for (const ThreadInfo* thread_info : thread_infos_) {
-      long rv = dispatch_semaphore_wait(thread_info->ready_semaphore,
-                                        DISPATCH_TIME_FOREVER);
-      ASSERT_EQ(0, rv);
+    for (ThreadInfo* thread_info : thread_infos_) {
+      thread_info->ready_semaphore.Wait();
     }
 
     // If present, suspend the thread at indices 1 through 3 the same number of
@@ -238,15 +236,12 @@ class TestThreadPool {
     ThreadInfo()
         : pthread(NULL),
           stack_address(0),
-          ready_semaphore(dispatch_semaphore_create(0)),
-          exit_semaphore(dispatch_semaphore_create(0)),
+          ready_semaphore(0),
+          exit_semaphore(0),
           suspend_count(0) {
     }
 
-    ~ThreadInfo() {
-      dispatch_release(exit_semaphore);
-      dispatch_release(ready_semaphore);
-    }
+    ~ThreadInfo() {}
 
     // The thread’s ID, set at the time the thread is created.
     pthread_t pthread;
@@ -259,12 +254,12 @@ class TestThreadPool {
     // setting up its ThreadInfo structure. The main thread waits on this
     // semaphore before using any data that the worker thread is responsible for
     // setting.
-    dispatch_semaphore_t ready_semaphore;
+    Semaphore ready_semaphore;
 
     // The worker thread waits on exit_semaphore to determine when it’s safe to
     // exit. The main thread signals exit_semaphore when it no longer needs the
     // worker thread.
-    dispatch_semaphore_t exit_semaphore;
+    Semaphore exit_semaphore;
 
     // The thread’s suspend count.
     int suspend_count;
@@ -276,8 +271,8 @@ class TestThreadPool {
     thread_info->stack_address =
         reinterpret_cast<mach_vm_address_t>(&thread_info);
 
-    dispatch_semaphore_signal(thread_info->ready_semaphore);
-    dispatch_semaphore_wait(thread_info->exit_semaphore, DISPATCH_TIME_FOREVER);
+    thread_info->ready_semaphore.Signal();
+    thread_info->exit_semaphore.Wait();
 
     // Check this here after everything’s known to be synchronized, otherwise
     // there’s a race between the parent thread storing this thread’s pthread_t

util/mach/exception_ports_test.cc

@@ -14,7 +14,6 @@
 
 #include "util/mach/exception_ports.h"
 
-#include <dispatch/dispatch.h>
 #include <mach/mach.h>
 #include <pthread.h>
 #include <signal.h>
@@ -30,6 +29,7 @@
 #include "util/mach/exc_server_variants.h"
 #include "util/mach/mach_extensions.h"
 #include "util/misc/scoped_forbid_return.h"
+#include "util/synchronization/semaphore.h"
 #include "util/test/mac/mach_errors.h"
 #include "util/test/mac/mach_multiprocess.h"
 
@@ -206,13 +206,10 @@ class TestExceptionPorts : public UniversalMachExcServer,
     explicit Child(TestExceptionPorts* test_exception_ports)
         : test_exception_ports_(test_exception_ports),
           thread_(),
-          init_semaphore_(dispatch_semaphore_create(0)),
-          crash_semaphore_(dispatch_semaphore_create(0)) {}
+          init_semaphore_(0),
+          crash_semaphore_(0) {}
 
-    ~Child() {
-      dispatch_release(crash_semaphore_);
-      dispatch_release(init_semaphore_);
-    }
+    ~Child() {}
 
     void Run() {
       ExceptionPorts self_task_ports(ExceptionPorts::kTargetTypeTask,
@@ -239,9 +236,7 @@ class TestExceptionPorts : public UniversalMachExcServer,
       ASSERT_EQ(0, rv_int);
 
       // Wait for the new thread to be ready.
-      long rv_long =
-          dispatch_semaphore_wait(init_semaphore_, DISPATCH_TIME_FOREVER);
-      ASSERT_EQ(0, rv_long);
+      init_semaphore_.Wait();
 
       // Tell the parent process that everything is set up.
       char c = '\0';
@@ -269,7 +264,7 @@ class TestExceptionPorts : public UniversalMachExcServer,
       }
 
       // Let the other thread know it’s safe to proceed.
-      dispatch_semaphore_signal(crash_semaphore_);
+      crash_semaphore_.Signal();
 
       // If this thread is the one that crashes, do it.
       if (test_exception_ports_->who_crashes() == kMainThreadCrashes) {
@@ -304,12 +299,10 @@ class TestExceptionPorts : public UniversalMachExcServer,
       }
 
       // Let the main thread know that this thread is ready.
-      dispatch_semaphore_signal(init_semaphore_);
+      init_semaphore_.Signal();
 
       // Wait for the main thread to signal that it’s safe to proceed.
-      long rv =
-          dispatch_semaphore_wait(crash_semaphore_, DISPATCH_TIME_FOREVER);
-      CHECK_EQ(0, rv) << "dispatch_semaphore_wait";
+      crash_semaphore_.Wait();
 
       // Regardless of where ExceptionPorts::SetExceptionPort() ran,
       // ExceptionPorts::GetExceptionPorts() can always be tested in-process.
@@ -344,11 +337,11 @@ class TestExceptionPorts : public UniversalMachExcServer,
 
     // The main thread waits on this for the other thread to start up and
     // perform its own initialization.
-    dispatch_semaphore_t init_semaphore_;
+    Semaphore init_semaphore_;
 
     // The child thread waits on this for the parent thread to indicate that the
     // child can test its exception ports and possibly crash, as appropriate.
-    dispatch_semaphore_t crash_semaphore_;
+    Semaphore crash_semaphore_;
 
     // Always zero. Crash() divides by this in order to trigger a crash. This is
     // structured as a static volatile int to ward off aggressive compiler

util/synchronization/semaphore.cc

@@ -0,0 +1,61 @@
+// 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/synchronization/semaphore.h"
+
+#include "base/logging.h"
+#include "base/posix/eintr_wrapper.h"
+
+namespace crashpad {
+
+#if defined(OS_MACOSX)
+
+Semaphore::Semaphore(int value)
+    : semaphore_(dispatch_semaphore_create(value)) {
+  CHECK(semaphore_) << "dispatch_semaphore_create";
+}
+
+Semaphore::~Semaphore() {
+  dispatch_release(semaphore_);
+}
+
+void Semaphore::Wait() {
+  CHECK_EQ(dispatch_semaphore_wait(semaphore_, DISPATCH_TIME_FOREVER), 0);
+}
+
+void Semaphore::Signal() {
+  dispatch_semaphore_signal(semaphore_);
+}
+
+#else
+
+Semaphore::Semaphore(int value) {
+  PCHECK(sem_init(&semaphore_, 0, value) == 0) << "sem_init";
+}
+
+Semaphore::~Semaphore() {
+  PCHECK(sem_destroy(&semaphore_)) << "sem_destroy";
+}
+
+void Semaphore::Wait() {
+  PCHECK(HANDLE_EINTR(sem_wait(&semaphore_))) << "sem_wait";
+}
+
+void Semaphore::Signal() {
+  PCHECK(sem_post(&semaphore_)) << "sem_post";
+}
+
+#endif
+
+}  // namespace crashpad

util/synchronization/semaphore.h

@@ -0,0 +1,63 @@
+// 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_SYNCHRONIZATION_SEMAPHORE_H_
+#define CRASHPAD_UTIL_SYNCHRONIZATION_SEMAPHORE_H_
+
+#include "build/build_config.h"
+
+#if defined(OS_MACOSX)
+#include <dispatch/dispatch.h>
+#else
+#include <semaphore.h>
+#endif
+
+namespace crashpad {
+
+//! \brief An anonymous in-process counting sempahore.
+class Semaphore {
+ public:
+  //! \brief Initializes the semaphore.
+  //!
+  //! \param[in] value The initial value of the semaphore.
+  //!
+  //! If the semaphore cannot be created, execution is terminated.
+  explicit Semaphore(int value);
+
+  ~Semaphore();
+
+  //! \brief Performs the wait (or “procure”) operation on the semaphore.
+  //!
+  //! Atomically decrements the value of the semaphore by 1. If the new value is
+  //! negative, this function blocks and will not return until the semaphore’s
+  //! value is incremented to 0 by Signal().
+  void Wait();
+
+  //! \brief Performs the signal (or “post”) operation on the semaphore.
+  //!
+  //! Atomically increments the value of the semaphore by 1. If the new value is
+  //! 0, a caller blocked in Wait() will be awakened.
+  void Signal();
+
+ private:
+#if defined(OS_MACOSX)
+  dispatch_semaphore_t semaphore_;
+#else
+  sem_t semaphore_;
+#endif
+};
+
+}  // namespace crashpad
+
+#endif  // CRASHPAD_UTIL_SYNCHRONIZATION_SEMAPHORE_H_

util/synchronization/semaphore_test.cc

@@ -0,0 +1,88 @@
+// 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/synchronization/semaphore.h"
+
+#include <pthread.h>
+
+#include "gtest/gtest.h"
+
+namespace {
+
+using namespace crashpad;
+
+TEST(Semaphore, Simple) {
+  Semaphore semaphore(1);
+  semaphore.Wait();
+  semaphore.Signal();
+}
+
+struct ThreadMainInfo {
+  pthread_t pthread;
+  Semaphore* semaphore;
+  size_t iterations;
+};
+
+void* ThreadMain(void* argument) {
+  ThreadMainInfo* info = reinterpret_cast<ThreadMainInfo*>(argument);
+  for (size_t iteration = 0; iteration < info->iterations; ++iteration) {
+    info->semaphore->Wait();
+  }
+  return NULL;
+}
+
+TEST(Semaphore, Threaded) {
+  Semaphore semaphore(0);
+  ThreadMainInfo info;
+  info.semaphore = &semaphore;
+  info.iterations = 1;
+
+  int rv = pthread_create(&info.pthread, NULL, ThreadMain, &info);
+  ASSERT_EQ(0, rv) << "pthread_create";
+
+  semaphore.Signal();
+
+  rv = pthread_join(info.pthread, NULL);
+  ASSERT_EQ(0, rv) << "pthread_join";
+}
+
+TEST(Semaphore, TenThreaded) {
+  // This test has a smaller initial value (5) than threads contending for these
+  // resources (10), and the threads each try to obtain the resource a different
+  // number of times.
+  Semaphore semaphore(5);
+  const size_t kThreads = 10;
+  ThreadMainInfo info[kThreads];
+  size_t iterations = 0;
+  int rv;
+  for (size_t index = 0; index < kThreads; ++index) {
+    info[index].semaphore = &semaphore;
+    info[index].iterations = index;
+    iterations += info[index].iterations;
+
+    rv = pthread_create(&info[index].pthread, NULL, ThreadMain, &info[index]);
+    ASSERT_EQ(0, rv) << "pthread_create";
+  }
+
+  for (size_t iteration = 0; iteration < iterations; ++iteration) {
+    semaphore.Signal();
+  }
+
+  for (size_t index = 0; index < kThreads; ++index) {
+    rv = pthread_join(info[index].pthread, NULL);
+    ASSERT_EQ(0, rv) << "pthread_join";
+  }
+}
+
+}  // namespace

util/util.gyp

@@ -107,6 +107,8 @@
         'stdlib/strlcpy.h',
         'stdlib/strnlen.cc',
         'stdlib/strnlen.h',
+        'synchronization/semaphore.cc',
+        'synchronization/semaphore.h',
       ],
       'actions': [
         {
@@ -226,6 +228,7 @@
         'stdlib/string_number_conversion_test.cc',
         'stdlib/strlcpy_test.cc',
         'stdlib/strnlen_test.cc',
+        'synchronization/semaphore_test.cc',
         'test/executable_path_test.cc',
         'test/mac/mach_multiprocess_test.cc',
         'test/multiprocess_exec_test.cc',