platform_system_core/init/signal_handler.cpp

/*
 * Copyright (C) 2010 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.
 */

#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <cutils/sockets.h>
#include <cutils/android_reboot.h>
#include <cutils/list.h>

#include "init.h"
#include "log.h"
#include "util.h"

static int signal_fd = -1;
static int signal_recv_fd = -1;

static void sigchld_handler(int s) {
    write(signal_fd, &s, 1);
}

#define CRITICAL_CRASH_THRESHOLD    4       /* if we crash >4 times ... */
#define CRITICAL_CRASH_WINDOW       (4*60)  /* ... in 4 minutes, goto recovery */

static int wait_for_one_process() {
    int status;
    pid_t pid = TEMP_FAILURE_RETRY(waitpid(-1, &status, WNOHANG));
    if (pid <= 0) {
        return -1;
    }
    INFO("waitpid returned pid %d, status = %08x\n", pid, status);

    service* svc = service_find_by_pid(pid);
    if (!svc) {
        if (WIFEXITED(status)) {
            ERROR("untracked pid %d exited with status %d\n", pid, WEXITSTATUS(status));
        } else if (WIFSIGNALED(status)) {
            ERROR("untracked pid %d killed by signal %d\n", pid, WTERMSIG(status));
        } else if (WIFSTOPPED(status)) {
            ERROR("untracked pid %d stopped by signal %d\n", pid, WSTOPSIG(status));
        } else {
            ERROR("untracked pid %d state changed\n", pid);
        }
        return 0;
    }

    // TODO: all the code from here down should be a member function on service.

    NOTICE("process '%s', pid %d exited\n", svc->name, pid);

    if (!(svc->flags & SVC_ONESHOT) || (svc->flags & SVC_RESTART)) {
        NOTICE("process '%s' killing any children in process group\n", svc->name);
        kill(-pid, SIGKILL);
    }

    // Remove any sockets we may have created.
    for (socketinfo* si = svc->sockets; si; si = si->next) {
        char tmp[128];
        snprintf(tmp, sizeof(tmp), ANDROID_SOCKET_DIR"/%s", si->name);
        unlink(tmp);
    }

    if (svc->flags & SVC_EXEC) {
        INFO("SVC_EXEC pid %d finished...\n", svc->pid);
        waiting_for_exec = false;
        list_remove(&svc->slist);
        free(svc->name);
        free(svc);
        return 0;
    }

    svc->pid = 0;
    svc->flags &= (~SVC_RUNNING);

    // Oneshot processes go into the disabled state on exit,
    // except when manually restarted.
    if ((svc->flags & SVC_ONESHOT) && !(svc->flags & SVC_RESTART)) {
        svc->flags |= SVC_DISABLED;
    }

    // Disabled and reset processes do not get restarted automatically.
    if (svc->flags & (SVC_DISABLED | SVC_RESET))  {
        svc->NotifyStateChange("stopped");
        return 0;
    }

    time_t now = gettime();
    if ((svc->flags & SVC_CRITICAL) && !(svc->flags & SVC_RESTART)) {
        if (svc->time_crashed + CRITICAL_CRASH_WINDOW >= now) {
            if (++svc->nr_crashed > CRITICAL_CRASH_THRESHOLD) {
                ERROR("critical process '%s' exited %d times in %d minutes; "
                      "rebooting into recovery mode\n", svc->name,
                      CRITICAL_CRASH_THRESHOLD, CRITICAL_CRASH_WINDOW / 60);
                android_reboot(ANDROID_RB_RESTART2, 0, "recovery");
                return 0;
            }
        } else {
            svc->time_crashed = now;
            svc->nr_crashed = 1;
        }
    }

    svc->flags &= (~SVC_RESTART);
    svc->flags |= SVC_RESTARTING;

    // Execute all onrestart commands for this service.
    struct listnode* node;
    list_for_each(node, &svc->onrestart.commands) {
        command* cmd = node_to_item(node, struct command, clist);
        cmd->func(cmd->nargs, cmd->args);
    }
    svc->NotifyStateChange("restarting");
    return 0;
}

void handle_signal() {
    // We got a SIGCHLD - reap and restart as needed.
    char tmp[32];
    read(signal_recv_fd, tmp, sizeof(tmp));
    while (!wait_for_one_process()) {
    }
}

void signal_init() {
    struct sigaction act;
    memset(&act, 0, sizeof(act));
    act.sa_handler = sigchld_handler;
    act.sa_flags = SA_NOCLDSTOP;
    sigaction(SIGCHLD, &act, 0);

    // Create a signalling mechanism for the sigchld handler.
    int s[2];
    if (socketpair(AF_UNIX, SOCK_STREAM | SOCK_NONBLOCK | SOCK_CLOEXEC, 0, s) == 0) {
        signal_fd = s[0];
        signal_recv_fd = s[1];
    }

    handle_signal();
}

int get_signal_fd() {
    return signal_recv_fd;
}