xref: /linux/tools/virtio/virtio-trace/trace-agent-rw.c (revision 75bf465f0bc33e9b776a46d6a1b9b990f5fb7c37)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Read/write thread of a guest agent 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 <stdio.h>
13 #include <stdlib.h>
14 #include <unistd.h>
15 #include <sys/syscall.h>
16 #include "trace-agent.h"
17 
18 #define READ_WAIT_USEC	100000
19 
rw_thread_info_new(void)20 void *rw_thread_info_new(void)
21 {
22 	struct rw_thread_info *rw_ti;
23 
24 	rw_ti = zalloc(sizeof(struct rw_thread_info));
25 	if (rw_ti == NULL) {
26 		pr_err("rw_thread_info zalloc error\n");
27 		exit(EXIT_FAILURE);
28 	}
29 
30 	rw_ti->cpu_num = -1;
31 	rw_ti->in_fd = -1;
32 	rw_ti->out_fd = -1;
33 	rw_ti->read_pipe = -1;
34 	rw_ti->write_pipe = -1;
35 	rw_ti->pipe_size = PIPE_INIT;
36 
37 	return rw_ti;
38 }
39 
rw_thread_init(int cpu,const char * in_path,const char * out_path,bool stdout_flag,unsigned long pipe_size,struct rw_thread_info * rw_ti)40 void *rw_thread_init(int cpu, const char *in_path, const char *out_path,
41 				bool stdout_flag, unsigned long pipe_size,
42 				struct rw_thread_info *rw_ti)
43 {
44 	int data_pipe[2];
45 
46 	rw_ti->cpu_num = cpu;
47 
48 	/* set read(input) fd */
49 	rw_ti->in_fd = open(in_path, O_RDONLY);
50 	if (rw_ti->in_fd == -1) {
51 		pr_err("Could not open in_fd (CPU:%d)\n", cpu);
52 		goto error;
53 	}
54 
55 	/* set write(output) fd */
56 	if (!stdout_flag) {
57 		/* virtio-serial output mode */
58 		rw_ti->out_fd = open(out_path, O_WRONLY);
59 		if (rw_ti->out_fd == -1) {
60 			pr_err("Could not open out_fd (CPU:%d)\n", cpu);
61 			goto error;
62 		}
63 	} else
64 		/* stdout mode */
65 		rw_ti->out_fd = STDOUT_FILENO;
66 
67 	if (pipe2(data_pipe, O_NONBLOCK) < 0) {
68 		pr_err("Could not create pipe in rw-thread(%d)\n", cpu);
69 		goto error;
70 	}
71 
72 	/*
73 	 * Size of pipe is 64kB in default based on fs/pipe.c.
74 	 * To read/write trace data speedy, pipe size is changed.
75 	 */
76 	if (fcntl(*data_pipe, F_SETPIPE_SZ, pipe_size) < 0) {
77 		pr_err("Could not change pipe size in rw-thread(%d)\n", cpu);
78 		goto error;
79 	}
80 
81 	rw_ti->read_pipe = data_pipe[1];
82 	rw_ti->write_pipe = data_pipe[0];
83 	rw_ti->pipe_size = pipe_size;
84 
85 	return NULL;
86 
87 error:
88 	exit(EXIT_FAILURE);
89 }
90 
91 /* Bind a thread to a cpu */
bind_cpu(int cpu_num)92 static void bind_cpu(int cpu_num)
93 {
94 	cpu_set_t mask;
95 
96 	CPU_ZERO(&mask);
97 	CPU_SET(cpu_num, &mask);
98 
99 	/* bind my thread to cpu_num by assigning zero to the first argument */
100 	if (sched_setaffinity(0, sizeof(mask), &mask) == -1)
101 		pr_err("Could not set CPU#%d affinity\n", (int)cpu_num);
102 }
103 
rw_thread_main(void * thread_info)104 static void *rw_thread_main(void *thread_info)
105 {
106 	ssize_t rlen, wlen;
107 	ssize_t ret;
108 	struct rw_thread_info *ts = (struct rw_thread_info *)thread_info;
109 
110 	bind_cpu(ts->cpu_num);
111 
112 	while (1) {
113 		/* Wait for a read order of trace data by Host OS */
114 		if (!global_run_operation) {
115 			pthread_mutex_lock(&mutex_notify);
116 			pthread_cond_wait(&cond_wakeup, &mutex_notify);
117 			pthread_mutex_unlock(&mutex_notify);
118 		}
119 
120 		if (global_sig_receive)
121 			break;
122 
123 		/*
124 		 * Each thread read trace_pipe_raw of each cpu bounding the
125 		 * thread, so contention of multi-threads does not occur.
126 		 */
127 		rlen = splice(ts->in_fd, NULL, ts->read_pipe, NULL,
128 				ts->pipe_size, SPLICE_F_MOVE | SPLICE_F_MORE);
129 
130 		if (rlen < 0) {
131 			pr_err("Splice_read in rw-thread(%d)\n", ts->cpu_num);
132 			goto error;
133 		} else if (rlen == 0) {
134 			/*
135 			 * If trace data do not exist or are unreadable not
136 			 * for exceeding the page size, splice_read returns
137 			 * NULL. Then, this waits for being filled the data in a
138 			 * ring-buffer.
139 			 */
140 			usleep(READ_WAIT_USEC);
141 			pr_debug("Read retry(cpu:%d)\n", ts->cpu_num);
142 			continue;
143 		}
144 
145 		wlen = 0;
146 
147 		do {
148 			ret = splice(ts->write_pipe, NULL, ts->out_fd, NULL,
149 					rlen - wlen,
150 					SPLICE_F_MOVE | SPLICE_F_MORE);
151 
152 			if (ret < 0) {
153 				pr_err("Splice_write in rw-thread(%d)\n",
154 								ts->cpu_num);
155 				goto error;
156 			} else if (ret == 0)
157 				/*
158 				 * When host reader is not in time for reading
159 				 * trace data, guest will be stopped. This is
160 				 * because char dev in QEMU is not supported
161 				 * non-blocking mode. Then, writer might be
162 				 * sleep in that case.
163 				 * This sleep will be removed by supporting
164 				 * non-blocking mode.
165 				 */
166 				sleep(1);
167 			wlen += ret;
168 		} while (wlen < rlen);
169 	}
170 
171 	return NULL;
172 
173 error:
174 	exit(EXIT_FAILURE);
175 }
176 
177 
rw_thread_run(struct rw_thread_info * rw_ti)178 pthread_t rw_thread_run(struct rw_thread_info *rw_ti)
179 {
180 	int ret;
181 	pthread_t rw_thread_per_cpu;
182 
183 	ret = pthread_create(&rw_thread_per_cpu, NULL, rw_thread_main, rw_ti);
184 	if (ret != 0) {
185 		pr_err("Could not create a rw thread(%d)\n", rw_ti->cpu_num);
186 		exit(EXIT_FAILURE);
187 	}
188 
189 	return rw_thread_per_cpu;
190 }
191