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 }
138