trace-agent-ctl.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Controller of read/write threads for virtio-trace
  4 *
  5 * Copyright (C) 2012 Hitachi, Ltd.
  6 * Created by Yoshihiro Yunomae <yoshihiro.yunomae.ez@hitachi.com>
  7 *            Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
  8 */
  9
 10#define _GNU_SOURCE
 11#include <fcntl.h>
 12#include <poll.h>
 13#include <signal.h>
 14#include <stdio.h>
 15#include <stdlib.h>
 16#include <unistd.h>
 17#include "trace-agent.h"
 18
 19#define HOST_MSG_SIZE		256
 20#define EVENT_WAIT_MSEC		100
 21
 22static volatile sig_atomic_t global_signal_val;
 23bool global_sig_receive;	/* default false */
 24bool global_run_operation;	/* default false*/
 25
 26/* Handle SIGTERM/SIGINT/SIGQUIT to exit */
 27static void signal_handler(int sig)
 28{
 29	global_signal_val = sig;
 30}
 31
 32int rw_ctl_init(const char *ctl_path)
 33{
 34	int ctl_fd;
 35
 36	ctl_fd = open(ctl_path, O_RDONLY);
 37	if (ctl_fd == -1) {
 38		pr_err("Cannot open ctl_fd\n");
 39		goto error;
 40	}
 41
 42	return ctl_fd;
 43
 44error:
 45	exit(EXIT_FAILURE);
 46}
 47
 48static int wait_order(int ctl_fd)
 49{
 50	struct pollfd poll_fd;
 51	int ret = 0;
 52
 53	while (!global_sig_receive) {
 54		poll_fd.fd = ctl_fd;
 55		poll_fd.events = POLLIN;
 56
 57		ret = poll(&poll_fd, 1, EVENT_WAIT_MSEC);
 58
 59		if (global_signal_val) {
 60			global_sig_receive = true;
 61			pr_info("Receive interrupt %d\n", global_signal_val);
 62
 63			/* Wakes rw-threads when they are sleeping */
 64			if (!global_run_operation)
 65				pthread_cond_broadcast(&cond_wakeup);
 66
 67			ret = -1;
 68			break;
 69		}
 70
 71		if (ret < 0) {
 72			pr_err("Polling error\n");
 73			goto error;
 74		}
 75
 76		if (ret)
 77			break;
 78	}
 79
 80	return ret;
 81
 82error:
 83	exit(EXIT_FAILURE);
 84}
 85
 86/*
 87 * contol read/write threads by handling global_run_operation
 88 */
 89void *rw_ctl_loop(int ctl_fd)
 90{
 91	ssize_t rlen;
 92	char buf[HOST_MSG_SIZE];
 93	int ret;
 94
 95	/* Setup signal handlers */
 96	signal(SIGTERM, signal_handler);
 97	signal(SIGINT, signal_handler);
 98	signal(SIGQUIT, signal_handler);
 99
100	while (!global_sig_receive) {
101
102		ret = wait_order(ctl_fd);
103		if (ret < 0)
104			break;
105
106		rlen = read(ctl_fd, buf, sizeof(buf));
107		if (rlen < 0) {
108			pr_err("read data error in ctl thread\n");
109			goto error;
110		}
111
112		if (rlen == 2 && buf[0] == '1') {
113			/*
114			 * If host writes '1' to a control path,
115			 * this controller wakes all read/write threads.
116			 */
117			global_run_operation = true;
118			pthread_cond_broadcast(&cond_wakeup);
119			pr_debug("Wake up all read/write threads\n");
120		} else if (rlen == 2 && buf[0] == '0') {
121			/*
122			 * If host writes '0' to a control path, read/write
123			 * threads will wait for notification from Host.
124			 */
125			global_run_operation = false;
126			pr_debug("Stop all read/write threads\n");
127		} else
128			pr_info("Invalid host notification: %s\n", buf);
129	}
130
131	return NULL;
132
133error:
134	exit(EXIT_FAILURE);
135}