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Add Win32 implementation for GNUmakeTokenPool
GNU make uses a semaphore as jobserver protocol on Win32. See also https://www.gnu.org/software/make/manual/html_node/Windows-Jobserver.html Usage is pretty simple and straightforward, i.e. WaitForSingleObject() to obtain a token and ReleaseSemaphore() to return it. Unfortunately subprocess-win32.cc uses an I/O completion port (IOCP). IOCPs aren't waitable objects, i.e. we can't use WaitForMultipleObjects() to wait on the IOCP and the token semaphore at the same time. Therefore GNUmakeTokenPoolWin32 creates a child thread that waits on the token semaphore and posts a dummy I/O completion status on the IOCP when it was able to obtain a token. That unblocks SubprocessSet::DoWork() and it can then check if a token became available or not. - split existing GNUmakeTokenPool into common and platform bits - add GNUmakeTokenPool interface - move the Posix bits to GNUmakeTokenPoolPosix - add the Win32 bits as GNUmakeTokenPoolWin32 - move Setup() method up to TokenPool interface - update Subprocess & TokenPool tests accordingly
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| // Copyright 2016-2018 Google Inc. 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. | ||
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| #include "tokenpool-gnu-make.h" | ||
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| #include <errno.h> | ||
| #include <fcntl.h> | ||
| #include <poll.h> | ||
| #include <unistd.h> | ||
| #include <signal.h> | ||
| #include <sys/time.h> | ||
| #include <stdio.h> | ||
| #include <string.h> | ||
| #include <stdlib.h> | ||
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| // TokenPool implementation for GNU make jobserver - POSIX implementation | ||
| // (http://make.mad-scientist.net/papers/jobserver-implementation/) | ||
| struct GNUmakeTokenPoolPosix : public GNUmakeTokenPool { | ||
| GNUmakeTokenPoolPosix(); | ||
| virtual ~GNUmakeTokenPoolPosix(); | ||
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| virtual int GetMonitorFd(); | ||
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| virtual const char *GetEnv(const char *name) { return getenv(name); }; | ||
| virtual bool ParseAuth(const char *jobserver); | ||
| virtual bool AcquireToken(); | ||
| virtual bool ReturnToken(); | ||
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| private: | ||
| int rfd_; | ||
| int wfd_; | ||
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| struct sigaction old_act_; | ||
| bool restore_; | ||
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| static int dup_rfd_; | ||
| static void CloseDupRfd(int signum); | ||
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| bool CheckFd(int fd); | ||
| bool SetAlarmHandler(); | ||
| }; | ||
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| GNUmakeTokenPoolPosix::GNUmakeTokenPoolPosix() : rfd_(-1), wfd_(-1), restore_(false) { | ||
| } | ||
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| GNUmakeTokenPoolPosix::~GNUmakeTokenPoolPosix() { | ||
| Clear(); | ||
| if (restore_) | ||
| sigaction(SIGALRM, &old_act_, NULL); | ||
| } | ||
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| bool GNUmakeTokenPoolPosix::CheckFd(int fd) { | ||
| if (fd < 0) | ||
| return false; | ||
| int ret = fcntl(fd, F_GETFD); | ||
| if (ret < 0) | ||
| return false; | ||
| return true; | ||
| } | ||
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| int GNUmakeTokenPoolPosix::dup_rfd_ = -1; | ||
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| void GNUmakeTokenPoolPosix::CloseDupRfd(int signum) { | ||
| close(dup_rfd_); | ||
| dup_rfd_ = -1; | ||
| } | ||
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| bool GNUmakeTokenPoolPosix::SetAlarmHandler() { | ||
| struct sigaction act; | ||
| memset(&act, 0, sizeof(act)); | ||
| act.sa_handler = CloseDupRfd; | ||
| if (sigaction(SIGALRM, &act, &old_act_) < 0) { | ||
| perror("sigaction:"); | ||
| return(false); | ||
| } else { | ||
| restore_ = true; | ||
| return(true); | ||
| } | ||
| } | ||
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| bool GNUmakeTokenPoolPosix::ParseAuth(const char *jobserver) { | ||
| int rfd = -1; | ||
| int wfd = -1; | ||
| if ((sscanf(jobserver, "%*[^=]=%d,%d", &rfd, &wfd) == 2) && | ||
| CheckFd(rfd) && | ||
| CheckFd(wfd) && | ||
| SetAlarmHandler()) { | ||
| rfd_ = rfd; | ||
| wfd_ = wfd; | ||
| return true; | ||
| } | ||
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| return false; | ||
| } | ||
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| bool GNUmakeTokenPoolPosix::AcquireToken() { | ||
| // Please read | ||
| // | ||
| // http://make.mad-scientist.net/papers/jobserver-implementation/ | ||
| // | ||
| // for the reasoning behind the following code. | ||
| // | ||
| // Try to read one character from the pipe. Returns true on success. | ||
| // | ||
| // First check if read() would succeed without blocking. | ||
| #ifdef USE_PPOLL | ||
| pollfd pollfds[] = {{rfd_, POLLIN, 0}}; | ||
| int ret = poll(pollfds, 1, 0); | ||
| #else | ||
| fd_set set; | ||
| struct timeval timeout = { 0, 0 }; | ||
| FD_ZERO(&set); | ||
| FD_SET(rfd_, &set); | ||
| int ret = select(rfd_ + 1, &set, NULL, NULL, &timeout); | ||
| #endif | ||
| if (ret > 0) { | ||
| // Handle potential race condition: | ||
| // - the above check succeeded, i.e. read() should not block | ||
| // - the character disappears before we call read() | ||
| // | ||
| // Create a duplicate of rfd_. The duplicate file descriptor dup_rfd_ | ||
| // can safely be closed by signal handlers without affecting rfd_. | ||
| dup_rfd_ = dup(rfd_); | ||
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| if (dup_rfd_ != -1) { | ||
| struct sigaction act, old_act; | ||
| int ret = 0; | ||
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| // Temporarily replace SIGCHLD handler with our own | ||
| memset(&act, 0, sizeof(act)); | ||
| act.sa_handler = CloseDupRfd; | ||
| if (sigaction(SIGCHLD, &act, &old_act) == 0) { | ||
| struct itimerval timeout; | ||
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| // install a 100ms timeout that generates SIGALARM on expiration | ||
| memset(&timeout, 0, sizeof(timeout)); | ||
| timeout.it_value.tv_usec = 100 * 1000; // [ms] -> [usec] | ||
| if (setitimer(ITIMER_REAL, &timeout, NULL) == 0) { | ||
| char buf; | ||
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| // Now try to read() from dup_rfd_. Return values from read(): | ||
| // | ||
| // 1. token read -> 1 | ||
| // 2. pipe closed -> 0 | ||
| // 3. alarm expires -> -1 (EINTR) | ||
| // 4. child exits -> -1 (EINTR) | ||
| // 5. alarm expired before entering read() -> -1 (EBADF) | ||
| // 6. child exited before entering read() -> -1 (EBADF) | ||
| // 7. child exited before handler is installed -> go to 1 - 3 | ||
| ret = read(dup_rfd_, &buf, 1); | ||
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| // disarm timer | ||
| memset(&timeout, 0, sizeof(timeout)); | ||
| setitimer(ITIMER_REAL, &timeout, NULL); | ||
| } | ||
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| sigaction(SIGCHLD, &old_act, NULL); | ||
| } | ||
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| CloseDupRfd(0); | ||
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| // Case 1 from above list | ||
| if (ret > 0) | ||
| return true; | ||
| } | ||
| } | ||
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| // read() would block, i.e. no token available, | ||
| // cases 2-6 from above list or | ||
| // select() / poll() / dup() / sigaction() / setitimer() failed | ||
| return false; | ||
| } | ||
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| bool GNUmakeTokenPoolPosix::ReturnToken() { | ||
| const char buf = '+'; | ||
| while (1) { | ||
| int ret = write(wfd_, &buf, 1); | ||
| if (ret > 0) | ||
| return true; | ||
| if ((ret != -1) || (errno != EINTR)) | ||
| return false; | ||
| // write got interrupted - retry | ||
| } | ||
| } | ||
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| int GNUmakeTokenPoolPosix::GetMonitorFd() { | ||
| return(rfd_); | ||
| } | ||
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| struct TokenPool *TokenPool::Get() { | ||
| return new GNUmakeTokenPoolPosix; | ||
| } |
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