trace-agent-ctl.c

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/*
 * Controller of read/write threads for virtio-trace
 *
 * Copyright (C) 2012 Hitachi, Ltd.
 * Created by Yoshihiro Yunomae <[email protected]>
 *            Masami Hiramatsu <[email protected]>
 *
 * Licensed under GPL version 2 only.
 *
 */

#define _GNU_SOURCE
#include <fcntl.h>
#include <poll.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include "trace-agent.h"

#define HOST_MSG_SIZE       256
#define EVENT_WAIT_MSEC     100

static volatile sig_atomic_t global_signal_val;
bool global_sig_receive;    /* default false */
bool global_run_operation;  /* default false*/

/* Handle SIGTERM/SIGINT/SIGQUIT to exit */
static void signal_handler(int sig)
{
    global_signal_val = sig;
}

int rw_ctl_init(const char *ctl_path)
{
    int ctl_fd;

    ctl_fd = open(ctl_path, O_RDONLY);
    if (ctl_fd == -1) {
        pr_err("Cannot open ctl_fd\n");
        goto error;
    }

    return ctl_fd;

error:
    exit(EXIT_FAILURE);
}

static int wait_order(int ctl_fd)
{
    struct pollfd poll_fd;
    int ret = 0;

    while (!global_sig_receive) {
        poll_fd.fd = ctl_fd;
        poll_fd.events = POLLIN;

        ret = poll(&poll_fd, 1, EVENT_WAIT_MSEC);

        if (global_signal_val) {
            global_sig_receive = true;
            pr_info("Receive interrupt %d\n", global_signal_val);

            /* Wakes rw-threads when they are sleeping */
            if (!global_run_operation)
                pthread_cond_broadcast(&cond_wakeup);

            ret = -1;
            break;
        }

        if (ret < 0) {
            pr_err("Polling error\n");
            goto error;
        }

        if (ret)
            break;
    };

    return ret;

error:
    exit(EXIT_FAILURE);
}

/*
 * contol read/write threads by handling global_run_operation
 */
void *rw_ctl_loop(int ctl_fd)
{
    ssize_t rlen;
    char buf[HOST_MSG_SIZE];
    int ret;

    /* Setup signal handlers */
    signal(SIGTERM, signal_handler);
    signal(SIGINT, signal_handler);
    signal(SIGQUIT, signal_handler);

    while (!global_sig_receive) {

        ret = wait_order(ctl_fd);
        if (ret < 0)
            break;

        rlen = read(ctl_fd, buf, sizeof(buf));
        if (rlen < 0) {
            pr_err("read data error in ctl thread\n");
            goto error;
        }

        if (rlen == 2 && buf[0] == '1') {
            /*
             * If host writes '1' to a control path,
             * this controller wakes all read/write threads.
             */
            global_run_operation = true;
            pthread_cond_broadcast(&cond_wakeup);
            pr_debug("Wake up all read/write threads\n");
        } else if (rlen == 2 && buf[0] == '0') {
            /*
             * If host writes '0' to a control path, read/write
             * threads will wait for notification from Host.
             */
            global_run_operation = false;
            pr_debug("Stop all read/write threads\n");
        } else
            pr_info("Invalid host notification: %s\n", buf);
    }

    return NULL;

error:
    exit(EXIT_FAILURE);
}