kernel/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
  24 static volatile sig_atomic_t global_signal_val;
  25 bool global_sig_receive;        /* default false */
  26 bool global_run_operation;      /* default false*/
  27
  28 /* Handle SIGTERM/SIGINT/SIGQUIT to exit */
  29 static void signal_handler(int sig)
  30 {
  31         global_signal_val = sig;
  32 }
  33
  34 int 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
  46 error:
  47         exit(EXIT_FAILURE);
  48 }
  49
  50 static 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
  84 error:
  85         exit(EXIT_FAILURE);
  86 }
  87
  88 /*
  89  * contol read/write threads by handling global_run_operation
  90  */
  91 void *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
 135 error:
 136         exit(EXIT_FAILURE);
 137 }