From 3d20beca6616095b2bc2952d645e7562410e79e5 Mon Sep 17 00:00:00 2001 From: Paul Elder Date: Wed, 10 Jul 2019 03:18:01 +0900 Subject: libcamera: Add Process and ProcessManager classes Add a Process class to abstract a process, and a ProcessManager singleton to monitor and manage the processes. Signed-off-by: Paul Elder Reviewed-by: Laurent Pinchart --- src/libcamera/include/process.h | 55 +++++++ src/libcamera/meson.build | 2 + src/libcamera/process.cpp | 357 ++++++++++++++++++++++++++++++++++++++++ 3 files changed, 414 insertions(+) create mode 100644 src/libcamera/include/process.h create mode 100644 src/libcamera/process.cpp (limited to 'src') diff --git a/src/libcamera/include/process.h b/src/libcamera/include/process.h new file mode 100644 index 00000000..d322fce1 --- /dev/null +++ b/src/libcamera/include/process.h @@ -0,0 +1,55 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ +/* + * Copyright (C) 2019, Google Inc. + * + * process.h - Process object + */ +#ifndef __LIBCAMERA_PROCESS_H__ +#define __LIBCAMERA_PROCESS_H__ + +#include +#include + +#include + +namespace libcamera { + +class Process final +{ +public: + enum ExitStatus { + NotExited, + NormalExit, + SignalExit, + }; + + Process(); + ~Process(); + + int start(const std::string &path, + const std::vector &args = std::vector(), + const std::vector &fds = std::vector()); + + ExitStatus exitStatus() const { return exitStatus_; } + int exitCode() const { return exitCode_; } + + void kill(); + + Signal finished; + +private: + void closeAllFdsExcept(const std::vector &fds); + int isolate(); + void died(int wstatus); + + pid_t pid_; + bool running_; + enum ExitStatus exitStatus_; + int exitCode_; + + friend class ProcessManager; +}; + +} /* namespace libcamera */ + +#endif /* __LIBCAMERA_PROCESS_H__ */ diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build index eda506b2..9eae6ce8 100644 --- a/src/libcamera/meson.build +++ b/src/libcamera/meson.build @@ -21,6 +21,7 @@ libcamera_sources = files([ 'message.cpp', 'object.cpp', 'pipeline_handler.cpp', + 'process.cpp', 'request.cpp', 'signal.cpp', 'stream.cpp', @@ -48,6 +49,7 @@ libcamera_headers = files([ 'include/media_object.h', 'include/message.h', 'include/pipeline_handler.h', + 'include/process.h', 'include/thread.h', 'include/utils.h', 'include/v4l2_device.h', diff --git a/src/libcamera/process.cpp b/src/libcamera/process.cpp new file mode 100644 index 00000000..9d8829d0 --- /dev/null +++ b/src/libcamera/process.cpp @@ -0,0 +1,357 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ +/* + * Copyright (C) 2019, Google Inc. + * + * process.cpp - Process object + */ + +#include "process.h" + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include + +#include "log.h" +#include "utils.h" + +/** + * \file process.h + * \brief Process object + */ + +namespace libcamera { + +LOG_DEFINE_CATEGORY(Process) + +/** + * \class ProcessManager + * \brief Manager of processes + * + * The ProcessManager singleton keeps track of all created Process instances, + * and manages the signal handling involved in terminating processes. + */ +class ProcessManager +{ +public: + void registerProcess(Process *proc); + + static ProcessManager *instance(); + + int writePipe() const; + + const struct sigaction &oldsa() const; + +private: + void sighandler(EventNotifier *notifier); + ProcessManager(); + ~ProcessManager(); + + std::list processes_; + + struct sigaction oldsa_; + EventNotifier *sigEvent_; + int pipe_[2]; +}; + +namespace { + +void sigact(int signal, siginfo_t *info, void *ucontext) +{ + char data = 0; + write(ProcessManager::instance()->writePipe(), &data, sizeof(data)); + + const struct sigaction &oldsa = ProcessManager::instance()->oldsa(); + if (oldsa.sa_flags & SA_SIGINFO) { + oldsa.sa_sigaction(signal, info, ucontext); + } else { + if (oldsa.sa_handler != SIG_IGN && oldsa.sa_handler != SIG_DFL) + oldsa.sa_handler(signal); + } +} + +} /* namespace */ + +void ProcessManager::sighandler(EventNotifier *notifier) +{ + char data; + read(pipe_[0], &data, sizeof(data)); + + for (auto it = processes_.begin(); it != processes_.end(); ) { + Process *process = *it; + + int wstatus; + pid_t pid = waitpid(process->pid_, &wstatus, WNOHANG); + if (process->pid_ != pid) { + ++it; + continue; + } + + it = processes_.erase(it); + process->died(wstatus); + } +} + +/** + * \brief Register process with process manager + * \param[in] proc Process to register + * + * This method registers the \a proc with the process manager. It + * shall be called by the parent process after successfully forking, in + * order to let the parent signal process termination. + */ +void ProcessManager::registerProcess(Process *proc) +{ + processes_.push_back(proc); +} + +ProcessManager::ProcessManager() +{ + sigaction(SIGCHLD, NULL, &oldsa_); + + struct sigaction sa; + memset(&sa, 0, sizeof(sa)); + sa.sa_sigaction = &sigact; + memcpy(&sa.sa_mask, &oldsa_.sa_mask, sizeof(sa.sa_mask)); + sigaddset(&sa.sa_mask, SIGCHLD); + sa.sa_flags = oldsa_.sa_flags | SA_SIGINFO; + + sigaction(SIGCHLD, &sa, NULL); + + pipe2(pipe_, O_CLOEXEC | O_DIRECT | O_NONBLOCK); + sigEvent_ = new EventNotifier(pipe_[0], EventNotifier::Read); + sigEvent_->activated.connect(this, &ProcessManager::sighandler); +} + +ProcessManager::~ProcessManager() +{ + sigaction(SIGCHLD, &oldsa_, NULL); + delete sigEvent_; + close(pipe_[0]); + close(pipe_[1]); +} + +/** + * \brief Retrieve the Process manager instance + * + * The ProcessManager is a singleton and can't be constructed manually. This + * method shall instead be used to retrieve the single global instance of the + * manager. + * + * \return The Process manager instance + */ +ProcessManager *ProcessManager::instance() +{ + static ProcessManager processManager; + return &processManager; +} + +/** + * \brief Retrieve the Process manager's write pipe + * + * This method is meant only to be used by the static signal handler. + * + * \return Pipe for writing + */ +int ProcessManager::writePipe() const +{ + return pipe_[1]; +} + +/** + * \brief Retrive the old signal action data + * + * This method is meant only to be used by the static signal handler. + * + * \return The old signal action data + */ +const struct sigaction &ProcessManager::oldsa() const +{ + return oldsa_; +} + + +/** + * \class Process + * \brief Process object + * + * The Process class models a process, and simplifies spawning new processes + * and monitoring the exiting of a process. + */ + +/** + * \enum Process::ExitStatus + * \brief Exit status of process + * \var Process::NotExited + * The process hasn't exited yet + * \var Process::NormalExit + * The process exited normally, either via exit() or returning from main + * \var Process::SignalExit + * The process was terminated by a signal (this includes crashing) + */ + +Process::Process() + : pid_(-1), running_(false), exitStatus_(NotExited), exitCode_(0) +{ +} + +Process::~Process() +{ + kill(); + /* \todo wait for child process to exit */ +} + +/** + * \brief Fork and exec a process, and close fds + * \param[in] path Path to executable + * \param[in] args Arguments to pass to executable (optional) + * \param[in] fds Vector of file descriptors to keep open (optional) + * + * Fork a process, and exec the executable specified by path. Prior to + * exec'ing, but after forking, all file descriptors except for those + * specified in fds will be closed. + * + * All indexes of args will be incremented by 1 before being fed to exec(), + * so args[0] should not need to be equal to path. + * + * \return Zero on successful fork, exec, and closing the file descriptors, + * or a negative error code otherwise + */ +int Process::start(const std::string &path, + const std::vector &args, + const std::vector &fds) +{ + int ret; + + if (running_) + return 0; + + int childPid = fork(); + if (childPid == -1) { + ret = -errno; + LOG(Process, Error) << "Failed to fork: " << strerror(-ret); + return ret; + } else if (childPid) { + pid_ = childPid; + ProcessManager::instance()->registerProcess(this); + + running_ = true; + + return 0; + } else { + if (isolate()) + _exit(EXIT_FAILURE); + + closeAllFdsExcept(fds); + + unsetenv("LIBCAMERA_LOG_FILE"); + + const char **argv = new const char *[args.size() + 2]; + unsigned int len = args.size(); + argv[0] = path.c_str(); + for (unsigned int i = 0; i < len; i++) + argv[i+1] = args[i].c_str(); + argv[len+1] = nullptr; + + execv(path.c_str(), (char **)argv); + + exit(EXIT_FAILURE); + } +} + +void Process::closeAllFdsExcept(const std::vector &fds) +{ + std::vector v(fds); + sort(v.begin(), v.end()); + + DIR *dir = opendir("/proc/self/fd"); + if (!dir) + return; + + int dfd = dirfd(dir); + + struct dirent *ent; + while ((ent = readdir(dir)) != nullptr) { + char *endp; + int fd = strtoul(ent->d_name, &endp, 10); + if (*endp) + continue; + + if (fd >= 0 && fd != dfd && + !std::binary_search(v.begin(), v.end(), fd)) + close(fd); + } + + closedir(dir); +} + +int Process::isolate() +{ + return unshare(CLONE_NEWUSER | CLONE_NEWNET); +} + +/** + * \brief SIGCHLD handler + * \param[in] wstatus The status as output by waitpid() + * + * This method is called when the process associated with Process terminates. + * It emits the Process::finished signal. + */ +void Process::died(int wstatus) +{ + running_ = false; + exitStatus_ = WIFEXITED(wstatus) ? NormalExit : SignalExit; + exitCode_ = exitStatus_ == NormalExit ? WEXITSTATUS(wstatus) : -1; + + finished.emit(this, exitStatus_, exitCode_); +} + +/** + * \fn Process::exitStatus() + * \brief Retrieve the exit status of the process + * + * Return the exit status of the process, that is, whether the process + * has exited via exit() or returning from main, or if the process was + * terminated by a signal. + * + * \sa ExitStatus + * + * \return The process exit status + */ + +/** + * \fn Process::exitCode() + * \brief Retrieve the exit code of the process + * + * This method is only valid if exitStatus() returned NormalExit. + * + * \return Exit code + */ + +/** + * \var Process::finished + * + * Signal that is emitted when the process is confirmed to have terminated. + */ + +/** + * \brief Kill the process + * + * Sends SIGKILL to the process. + */ +void Process::kill() +{ + ::kill(pid_, SIGKILL); +} + +} /* namespace libcamera */ -- cgit v1.2.1