worker.cpp

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/*
 * Zth (libzth), a cooperative userspace multitasking library.
 * Copyright (C) 2019-2022  Jochem Rutgers
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/.
 */
 
#include <libzth/worker.h>
 
#include <libzth/async.h>
 
#include <csignal>
#include <vector>
 
#ifndef ZTH_OS_WINDOWS
#       include <sys/types.h>
#       include <sys/wait.h>
#       include <unistd.h>
#endif
 
#ifdef ZTH_OS_MAC
#       include <crt_externs.h>
#       define environ (*_NSGetEnviron())
#endif
 
namespace zth {
 
#if !defined(ZTH_OS_WINDOWS) && !defined(ZTH_OS_BAREMETAL)
static void sigchld_handler(int /*unused*/);
#endif
 
void worker_global_init()
{
        zth_dbg(banner, "%s", banner());
#if !defined(ZTH_OS_WINDOWS) && !defined(ZTH_OS_BAREMETAL)
#       ifdef ZTH_USE_VALGRIND
        // valgrind does not seem to like the sigaction below. Not sure why.
        if(!RUNNING_ON_VALGRIND) // NOLINT(hicpp-no-assembler)
#       endif
        {
                struct sigaction sa = {};
                sa.sa_handler = &sigchld_handler;
                sigaction(SIGCHLD, &sa, nullptr);
        }
#endif
}
ZTH_INIT_CALL(worker_global_init)
 
#ifdef ZTH_USE_PTHREAD
static void* worker_main(void* fiber)
{
        Worker w;
        w << (Fiber*)fiber;
        w.run();
        return nullptr;
}
#endif
 
int startWorkerThread(
        UNUSED_PAR(void (*f)()), size_t UNUSED_PAR(stack), char const* UNUSED_PAR(name))
{
#ifdef ZTH_USE_PTHREAD
        pthread_t t;
        int res = 0;
 
        zth_dbg(thread, "[%s] starting new Worker", thread_id_str().c_str());
 
        Fiber* fiber = new Fiber((void (*)(void*))f, nullptr);
        if(stack)
                if((res = fiber->setStackSize(stack)))
                        return res;
 
        if(name)
                fiber->setName(name);
 
        if((res = pthread_create(&t, nullptr, &worker_main, (void*)fiber)))
                return res;
 
        pthread_detach(t);
        return 0;
#else
        return ENOSYS;
#endif
}
 
int execlp(char const* file, char const* arg, ... /*, nullptr */)
{
        small_vector<char*, 8> argv;
        int res = 0;
 
        try {
                va_list args;
                va_start(args, arg);
                while(true) {
                        char const* a = va_arg(args, char const*);
                        if(!a) {
                                argv.push_back(nullptr);
                                break;
                        } else {
                                char* argcopy = strdup(a);
                                if(!argcopy) {
                                        res = ENOMEM;
                                        break;
                                }
                                argv.push_back(argcopy);
                        }
                }
                va_end(args);
        } catch(std::bad_alloc const&) {
                res = ENOMEM;
        } catch(...) {
                res = EAGAIN;
        }
 
        if(!res)
                res = execvp(file, argv.data());
 
        for(size_t i = 0; i < argv.size(); i++)
                if(argv[i])
                        free(argv[i]);
 
        return res;
}
 
__attribute__((unused)) static cow_string thread_id_str() noexcept
{
        Worker* w = Worker::instance();
        if(w)
                return w->id_str();
 
        return format(
                "pid %u",
#ifdef ZTH_OS_WINDOWS
                (unsigned int)_getpid()
#else
                (unsigned int)getpid()
#endif
        );
}
 
int execvp(char const* UNUSED_PAR(file), char* const UNUSED_PAR(arg[]))
{
#if defined(ZTH_OS_WINDOWS) || defined(ZTH_OS_BAREMETAL)
        return ENOSYS;
#else
        perf_syscall("execvp()");
        zth_dbg(thread, "[%s] execvp %s", thread_id_str().c_str(), file);
 
        pid_t pid = 0;
        if((pid = fork()) == 0) {
                // In child.
                execve(file, arg, environ);
                // If we get here, we could not create the process.
                _exit(127);
                // Unreachable.
                return EAGAIN;
        } else if(pid == -1) {
                int res = errno;
                zth_dbg(thread, "[%s] Could not fork(); %s", thread_id_str().c_str(),
                        err(res).c_str());
                return res;
        } else
                return 0;
#endif
}
 
#if !defined(ZTH_OS_WINDOWS) && !defined(ZTH_OS_BAREMETAL)
static volatile sig_atomic_t sigchld_cleanup = 0;
 
static void sigchld_handler(int /*unused*/)
{
        sigchld_cleanup = 1;
}
#endif
 
void sigchld_check()
{
#if !defined(ZTH_OS_WINDOWS) && !defined(ZTH_OS_BAREMETAL)
#       ifdef ZTH_USE_VALGRIND
        // The sigaction was disabled, so sigchld_cleanup will always be 0.
        if(!RUNNING_ON_VALGRIND) // NOLINT(hicpp-no-assembler)
#       endif
                if(likely(sigchld_cleanup == 0))
                        return;
 
        Worker* w = Worker::instance();
        char const* id_str = w ? w->id_str() : "?";
 
        while(true) {
                sigchld_cleanup = 0;
                int wstatus = 0;
                pid_t pid = waitpid(-1, &wstatus, WNOHANG);
 
                if(pid == 0) {
                        // No (other) child exited.
                        return;
                } else if(pid == -1) {
                        zth_dbg(worker, "[%s] waitpid() failed; %s", id_str, err(errno).c_str());
                        return;
                } else {
                        zth_dbg(worker, "[%s] Child process %u terminated with exit code %d",
                                id_str, (unsigned int)pid, wstatus);
                }
        }
#endif
}
 
} // namespace zth