Merge "liblog: remove Rwlocks for logd_socket and pmsg_fd" am: 3e86e250bb am: d4b964b001 (c51910e1) · Commits · e / os / android_system_core

liblog/include/log/log.h

+5 −2

Original line number	Diff line number	Diff line
		@@ -144,8 +144,11 @@ clockid_t android_log_clockid(void);
		/*
		* Release any logger resources (a new log write will immediately re-acquire)
		*
		* May be used to clean up File descriptors after a Fork, the resources are
		* all O_CLOEXEC so wil self clean on exec().
		* This is specifically meant to be used by Zygote to close open file descriptors after fork()
		* and before specialization. O_CLOEXEC is used on file descriptors, so they will be closed upon
		* exec() in normal use cases.
		*
		* Note that this is not safe to call from a multi-threaded program.
		*/
		void __android_log_close(void);

liblog/logd_writer.cpp

+28 −41

Original line number	Diff line number	Diff line
		@@ -32,58 +32,53 @@
		#include <time.h>
		#include <unistd.h>

		#include <shared_mutex>

		#include <private/android_filesystem_config.h>
		#include <private/android_logger.h>

		#include "logger.h"
		#include "rwlock.h"
		#include "uio.h"

		static int logd_socket;
		static RwLock logd_socket_lock;

		static void OpenSocketLocked() {
		logd_socket = TEMP_FAILURE_RETRY(socket(PF_UNIX, SOCK_DGRAM \| SOCK_CLOEXEC \| SOCK_NONBLOCK, 0));
		if (logd_socket <= 0) {
		return;
		}
		static atomic_int logd_socket;

		// Note that it is safe to call connect() multiple times on DGRAM Unix domain sockets, so this
		// function is used to reconnect to logd without requiring a new socket.
		static void LogdConnect() {
		sockaddr_un un = {};
		un.sun_family = AF_UNIX;
		strcpy(un.sun_path, "/dev/socket/logdw");

		if (TEMP_FAILURE_RETRY(
		connect(logd_socket, reinterpret_cast<sockaddr*>(&un), sizeof(sockaddr_un))) < 0) {
		close(logd_socket);
		logd_socket = 0;
		}
		TEMP_FAILURE_RETRY(connect(logd_socket, reinterpret_cast<sockaddr*>(&un), sizeof(sockaddr_un)));
		}

		static void OpenSocket() {
		auto lock = std::unique_lock{logd_socket_lock};
		if (logd_socket > 0) {
		// Someone raced us and opened the socket already.
		// logd_socket should only be opened once. If we see that logd_socket is uninitialized, we create a
		// new socket and attempt to exchange it into the atomic logd_socket. If the compare/exchange was
		// successful, then that will be the socket used for the duration of the program, otherwise a
		// different thread has already opened and written the socket to the atomic, so close the new socket
		// and return.
		static void GetSocket() {
		if (logd_socket != 0) {
		return;
		}

		OpenSocketLocked();
		int new_socket =
		TEMP_FAILURE_RETRY(socket(PF_UNIX, SOCK_DGRAM \| SOCK_CLOEXEC \| SOCK_NONBLOCK, 0));
		if (new_socket <= 0) {
		return;
		}

		static void ResetSocket(int old_socket) {
		auto lock = std::unique_lock{logd_socket_lock};
		if (old_socket != logd_socket) {
		// Someone raced us and reset the socket already.
		int uninitialized_value = 0;
		if (!logd_socket.compare_exchange_strong(uninitialized_value, new_socket)) {
		close(new_socket);
		return;
		}
		close(logd_socket);
		logd_socket = 0;
		OpenSocketLocked();

		LogdConnect();
		}

		// This is the one exception to the above. Zygote uses this to clean up open FD's after fork() and
		// before specialization. It is single threaded at this point and therefore this function is
		// explicitly not thread safe. It sets logd_socket to 0, so future logs will be safely initialized
		// whenever they happen.
		void LogdClose() {
		auto lock = std::unique_lock{logd_socket_lock};
		if (logd_socket > 0) {
		close(logd_socket);
		}
		@@ -99,12 +94,7 @@ int LogdWrite(log_id_t logId, struct timespec* ts, struct iovec* vec, size_t nr)
		static atomic_int dropped;
		static atomic_int droppedSecurity;

		auto lock = std::shared_lock{logd_socket_lock};
		if (logd_socket <= 0) {
		lock.unlock();
		OpenSocket();
		lock.lock();
		}
		GetSocket();

		if (logd_socket <= 0) {
		return -EBADF;
		@@ -183,10 +173,7 @@ int LogdWrite(log_id_t logId, struct timespec* ts, struct iovec* vec, size_t nr)
		// the connection, so we reset it and try again.
		ret = TEMP_FAILURE_RETRY(writev(logd_socket, newVec, i));
		if (ret < 0 && errno != EAGAIN) {
		int old_socket = logd_socket;
		lock.unlock();
		ResetSocket(old_socket);
		lock.lock();
		LogdConnect();

		ret = TEMP_FAILURE_RETRY(writev(logd_socket, newVec, i));
		}

liblog/pmsg_writer.cpp

+18 −18

Original line number	Diff line number	Diff line
		@@ -23,30 +23,36 @@
		#include <sys/types.h>
		#include <time.h>

		#include <shared_mutex>

		#include <log/log_properties.h>
		#include <private/android_logger.h>

		#include "logger.h"
		#include "rwlock.h"
		#include "uio.h"

		static int pmsg_fd;
		static RwLock pmsg_fd_lock;
		static atomic_int pmsg_fd;

		static void PmsgOpen() {
		auto lock = std::unique_lock{pmsg_fd_lock};
		if (pmsg_fd > 0) {
		// Someone raced us and opened the socket already.
		// pmsg_fd should only beopened once. If we see that pmsg_fd is uninitialized, we open "/dev/pmsg0"
		// then attempt to compare/exchange it into pmsg_fd. If the compare/exchange was successful, then
		// that will be the fd used for the duration of the program, otherwise a different thread has
		// already opened and written the fd to the atomic, so close the new fd and return.
		static void GetPmsgFd() {
		if (pmsg_fd != 0) {
		return;
		}

		int new_fd = TEMP_FAILURE_RETRY(open("/dev/pmsg0", O_WRONLY \| O_CLOEXEC));
		if (new_fd <= 0) {
		return;
		}

		pmsg_fd = TEMP_FAILURE_RETRY(open("/dev/pmsg0", O_WRONLY \| O_CLOEXEC));
		int uninitialized_value = 0;
		if (!pmsg_fd.compare_exchange_strong(uninitialized_value, new_fd)) {
		close(new_fd);
		return;
		}
		}

		void PmsgClose() {
		auto lock = std::unique_lock{pmsg_fd_lock};
		if (pmsg_fd > 0) {
		close(pmsg_fd);
		}
		@@ -77,13 +83,7 @@ int PmsgWrite(log_id_t logId, struct timespec* ts, struct iovec* vec, size_t nr)
		}
		}

		auto lock = std::shared_lock{pmsg_fd_lock};

		if (pmsg_fd <= 0) {
		lock.unlock();
		PmsgOpen();
		lock.lock();
		}
		GetPmsgFd();

		if (pmsg_fd <= 0) {
		return -EBADF;

liblog/rwlock.h

deleted100644 → 0

+0 −39

Original line number	Diff line number	Diff line
		/*
		* Copyright (C) 2019 The Android Open Source Project
		*
		* 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.
		*/

		#pragma once

		#include <pthread.h>

		// As of the end of Dec 2019, std::shared_mutex is not simply a pthread_rwlock, but rather a
		// combination of std::mutex and std::condition variable, which is obviously less efficient. This
		// immitates what std::shared_mutex should be doing and is compatible with std::shared_lock and
		// std::unique_lock.

		class RwLock {
		public:
		RwLock() {}
		~RwLock() {}

		void lock() { pthread_rwlock_wrlock(&rwlock_); }
		void unlock() { pthread_rwlock_unlock(&rwlock_); }

		void lock_shared() { pthread_rwlock_rdlock(&rwlock_); }
		void unlock_shared() { pthread_rwlock_unlock(&rwlock_); }

		private:
		pthread_rwlock_t rwlock_ = PTHREAD_RWLOCK_INITIALIZER;
		};

liblog/tests/Android.bp

+1 −2

Original line number	Diff line number	Diff line
		@@ -63,8 +63,8 @@ cc_defaults {
		"log_system_test.cpp",
		"log_time_test.cpp",
		"log_wrap_test.cpp",
		"logd_writer_test.cpp",
		"logprint_test.cpp",
		"rwlock_test.cpp",
		],
		shared_libs: [
		"libcutils",
		@@ -108,7 +108,6 @@ cc_test_host {
		"liblog_host_test.cpp",
		"liblog_default_tag.cpp",
		"liblog_global_state.cpp",
		"rwlock_test.cpp",
		],
		isolated: true,
		}