LXR linux/tools/virtio/virtio-trace/trace-agent-ctl.c

   1/*
   2 * Controller of read/write threads for virtio-trace
   3 *
   4 * Copyright (C) 2012 Hitachi, Ltd.
   5 * Created by Yoshihiro Yunomae <yoshihiro.yunomae.ez@hitachi.com>
   6 *            Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
   7 *
   8 * Licensed under GPL version 2 only.
   9 *
  10 */
  11
  12#define _GNU_SOURCE
  13#include <fcntl.h>
  14#include <poll.h>
  15#include <signal.h>
  16#include <stdio.h>
  17#include <stdlib.h>
  18#include <unistd.h>
  19#include "trace-agent.h"
  20
  21#define HOST_MSG_SIZE           256
  22#define EVENT_WAIT_MSEC         100
  23
  24static volatile sig_atomic_t global_signal_val;
  25bool global_sig_receive;        /* default false */
  26bool global_run_operation;      /* default false*/
  27
  28/* Handle SIGTERM/SIGINT/SIGQUIT to exit */
  29static void signal_handler(int sig)
  30{
  31        global_signal_val = sig;
  32}
  33
  34int rw_ctl_init(const char *ctl_path)
  35{
  36        int ctl_fd;
  37
  38        ctl_fd = open(ctl_path, O_RDONLY);
  39        if (ctl_fd == -1) {
  40                pr_err("Cannot open ctl_fd\n");
  41                goto error;
  42        }
  43
  44        return ctl_fd;
  45
  46error:
  47        exit(EXIT_FAILURE);
  48}
  49
  50static int wait_order(int ctl_fd)
  51{
  52        struct pollfd poll_fd;
  53        int ret = 0;
  54
  55        while (!global_sig_receive) {
  56                poll_fd.fd = ctl_fd;
  57                poll_fd.events = POLLIN;
  58
  59                ret = poll(&poll_fd, 1, EVENT_WAIT_MSEC);
  60
  61                if (global_signal_val) {
  62                        global_sig_receive = true;
  63                        pr_info("Receive interrupt %d\n", global_signal_val);
  64
  65                        /* Wakes rw-threads when they are sleeping */
  66                        if (!global_run_operation)
  67                                pthread_cond_broadcast(&cond_wakeup);
  68
  69                        ret = -1;
  70                        break;
  71                }
  72
  73                if (ret < 0) {
  74                        pr_err("Polling error\n");
  75                        goto error;
  76                }
  77
  78                if (ret)
  79                        break;
  80        };
  81
  82        return ret;
  83
  84error:
  85        exit(EXIT_FAILURE);
  86}
  87
  88/*
  89 * contol read/write threads by handling global_run_operation
  90 */
  91void *rw_ctl_loop(int ctl_fd)
  92{
  93        ssize_t rlen;
  94        char buf[HOST_MSG_SIZE];
  95        int ret;
  96
  97        /* Setup signal handlers */
  98        signal(SIGTERM, signal_handler);
  99        signal(SIGINT, signal_handler);
 100        signal(SIGQUIT, signal_handler);
 101
 102        while (!global_sig_receive) {
 103
 104                ret = wait_order(ctl_fd);
 105                if (ret < 0)
 106                        break;
 107
 108                rlen = read(ctl_fd, buf, sizeof(buf));
 109                if (rlen < 0) {
 110                        pr_err("read data error in ctl thread\n");
 111                        goto error;
 112                }
 113
 114                if (rlen == 2 && buf[0] == '1') {
 115                        /*
 116                         * If host writes '1' to a control path,
 117                         * this controller wakes all read/write threads.
 118                         */
 119                        global_run_operation = true;
 120                        pthread_cond_broadcast(&cond_wakeup);
 121                        pr_debug("Wake up all read/write threads\n");
 122                } else if (rlen == 2 && buf[0] == '0') {
 123                        /*
 124                         * If host writes '0' to a control path, read/write
 125                         * threads will wait for notification from Host.
 126                         */
 127                        global_run_operation = false;
 128                        pr_debug("Stop all read/write threads\n");
 129                } else
 130                        pr_info("Invalid host notification: %s\n", buf);
 131        }
 132
 133        return NULL;
 134
 135error:
 136        exit(EXIT_FAILURE);
 137}
 138