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Linux/tools/virtio/virtio-trace/trace-agent-rw.c

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  1 /*
  2  * Read/write thread of a guest agent 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 <stdio.h>
 15 #include <stdlib.h>
 16 #include <unistd.h>
 17 #include <sys/syscall.h>
 18 #include "trace-agent.h"
 19 
 20 #define READ_WAIT_USEC  100000
 21 
 22 void *rw_thread_info_new(void)
 23 {
 24         struct rw_thread_info *rw_ti;
 25 
 26         rw_ti = zalloc(sizeof(struct rw_thread_info));
 27         if (rw_ti == NULL) {
 28                 pr_err("rw_thread_info zalloc error\n");
 29                 exit(EXIT_FAILURE);
 30         }
 31 
 32         rw_ti->cpu_num = -1;
 33         rw_ti->in_fd = -1;
 34         rw_ti->out_fd = -1;
 35         rw_ti->read_pipe = -1;
 36         rw_ti->write_pipe = -1;
 37         rw_ti->pipe_size = PIPE_INIT;
 38 
 39         return rw_ti;
 40 }
 41 
 42 void *rw_thread_init(int cpu, const char *in_path, const char *out_path,
 43                                 bool stdout_flag, unsigned long pipe_size,
 44                                 struct rw_thread_info *rw_ti)
 45 {
 46         int data_pipe[2];
 47 
 48         rw_ti->cpu_num = cpu;
 49 
 50         /* set read(input) fd */
 51         rw_ti->in_fd = open(in_path, O_RDONLY);
 52         if (rw_ti->in_fd == -1) {
 53                 pr_err("Could not open in_fd (CPU:%d)\n", cpu);
 54                 goto error;
 55         }
 56 
 57         /* set write(output) fd */
 58         if (!stdout_flag) {
 59                 /* virtio-serial output mode */
 60                 rw_ti->out_fd = open(out_path, O_WRONLY);
 61                 if (rw_ti->out_fd == -1) {
 62                         pr_err("Could not open out_fd (CPU:%d)\n", cpu);
 63                         goto error;
 64                 }
 65         } else
 66                 /* stdout mode */
 67                 rw_ti->out_fd = STDOUT_FILENO;
 68 
 69         if (pipe2(data_pipe, O_NONBLOCK) < 0) {
 70                 pr_err("Could not create pipe in rw-thread(%d)\n", cpu);
 71                 goto error;
 72         }
 73 
 74         /*
 75          * Size of pipe is 64kB in default based on fs/pipe.c.
 76          * To read/write trace data speedy, pipe size is changed.
 77          */
 78         if (fcntl(*data_pipe, F_SETPIPE_SZ, pipe_size) < 0) {
 79                 pr_err("Could not change pipe size in rw-thread(%d)\n", cpu);
 80                 goto error;
 81         }
 82 
 83         rw_ti->read_pipe = data_pipe[1];
 84         rw_ti->write_pipe = data_pipe[0];
 85         rw_ti->pipe_size = pipe_size;
 86 
 87         return NULL;
 88 
 89 error:
 90         exit(EXIT_FAILURE);
 91 }
 92 
 93 /* Bind a thread to a cpu */
 94 static void bind_cpu(int cpu_num)
 95 {
 96         cpu_set_t mask;
 97 
 98         CPU_ZERO(&mask);
 99         CPU_SET(cpu_num, &mask);
100 
101         /* bind my thread to cpu_num by assigning zero to the first argument */
102         if (sched_setaffinity(0, sizeof(mask), &mask) == -1)
103                 pr_err("Could not set CPU#%d affinity\n", (int)cpu_num);
104 }
105 
106 static void *rw_thread_main(void *thread_info)
107 {
108         ssize_t rlen, wlen;
109         ssize_t ret;
110         struct rw_thread_info *ts = (struct rw_thread_info *)thread_info;
111 
112         bind_cpu(ts->cpu_num);
113 
114         while (1) {
115                 /* Wait for a read order of trace data by Host OS */
116                 if (!global_run_operation) {
117                         pthread_mutex_lock(&mutex_notify);
118                         pthread_cond_wait(&cond_wakeup, &mutex_notify);
119                         pthread_mutex_unlock(&mutex_notify);
120                 }
121 
122                 if (global_sig_receive)
123                         break;
124 
125                 /*
126                  * Each thread read trace_pipe_raw of each cpu bounding the
127                  * thread, so contention of multi-threads does not occur.
128                  */
129                 rlen = splice(ts->in_fd, NULL, ts->read_pipe, NULL,
130                                 ts->pipe_size, SPLICE_F_MOVE | SPLICE_F_MORE);
131 
132                 if (rlen < 0) {
133                         pr_err("Splice_read in rw-thread(%d)\n", ts->cpu_num);
134                         goto error;
135                 } else if (rlen == 0) {
136                         /*
137                          * If trace data do not exist or are unreadable not
138                          * for exceeding the page size, splice_read returns
139                          * NULL. Then, this waits for being filled the data in a
140                          * ring-buffer.
141                          */
142                         usleep(READ_WAIT_USEC);
143                         pr_debug("Read retry(cpu:%d)\n", ts->cpu_num);
144                         continue;
145                 }
146 
147                 wlen = 0;
148 
149                 do {
150                         ret = splice(ts->write_pipe, NULL, ts->out_fd, NULL,
151                                         rlen - wlen,
152                                         SPLICE_F_MOVE | SPLICE_F_MORE);
153 
154                         if (ret < 0) {
155                                 pr_err("Splice_write in rw-thread(%d)\n",
156                                                                 ts->cpu_num);
157                                 goto error;
158                         } else if (ret == 0)
159                                 /*
160                                  * When host reader is not in time for reading
161                                  * trace data, guest will be stopped. This is
162                                  * because char dev in QEMU is not supported
163                                  * non-blocking mode. Then, writer might be
164                                  * sleep in that case.
165                                  * This sleep will be removed by supporting
166                                  * non-blocking mode.
167                                  */
168                                 sleep(1);
169                         wlen += ret;
170                 } while (wlen < rlen);
171         }
172 
173         return NULL;
174 
175 error:
176         exit(EXIT_FAILURE);
177 }
178 
179 
180 pthread_t rw_thread_run(struct rw_thread_info *rw_ti)
181 {
182         int ret;
183         pthread_t rw_thread_per_cpu;
184 
185         ret = pthread_create(&rw_thread_per_cpu, NULL, rw_thread_main, rw_ti);
186         if (ret != 0) {
187                 pr_err("Could not create a rw thread(%d)\n", rw_ti->cpu_num);
188                 exit(EXIT_FAILURE);
189         }
190 
191         return rw_thread_per_cpu;
192 }
193 

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