trace-agent-rw.c
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/*
* Read/write thread of a guest agent for virtio-trace
*
* Copyright (C) 2012 Hitachi, Ltd.
* Created by Yoshihiro Yunomae <yoshihiro.yunomae.ez@hitachi.com>
* Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
*
* Licensed under GPL version 2 only.
*
*/
#define _GNU_SOURCE
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/syscall.h>
#include "trace-agent.h"
#define READ_WAIT_USEC 100000
void *rw_thread_info_new(void)
{
struct rw_thread_info *rw_ti;
rw_ti = zalloc(sizeof(struct rw_thread_info));
if (rw_ti == NULL) {
pr_err("rw_thread_info zalloc error\n");
exit(EXIT_FAILURE);
}
rw_ti->cpu_num = -1;
rw_ti->in_fd = -1;
rw_ti->out_fd = -1;
rw_ti->read_pipe = -1;
rw_ti->write_pipe = -1;
rw_ti->pipe_size = PIPE_INIT;
return rw_ti;
}
void *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)
{
int data_pipe[2];
rw_ti->cpu_num = cpu;
/* set read(input) fd */
rw_ti->in_fd = open(in_path, O_RDONLY);
if (rw_ti->in_fd == -1) {
pr_err("Could not open in_fd (CPU:%d)\n", cpu);
goto error;
}
/* set write(output) fd */
if (!stdout_flag) {
/* virtio-serial output mode */
rw_ti->out_fd = open(out_path, O_WRONLY);
if (rw_ti->out_fd == -1) {
pr_err("Could not open out_fd (CPU:%d)\n", cpu);
goto error;
}
} else
/* stdout mode */
rw_ti->out_fd = STDOUT_FILENO;
if (pipe2(data_pipe, O_NONBLOCK) < 0) {
pr_err("Could not create pipe in rw-thread(%d)\n", cpu);
goto error;
}
/*
* Size of pipe is 64kB in default based on fs/pipe.c.
* To read/write trace data speedy, pipe size is changed.
*/
if (fcntl(*data_pipe, F_SETPIPE_SZ, pipe_size) < 0) {
pr_err("Could not change pipe size in rw-thread(%d)\n", cpu);
goto error;
}
rw_ti->read_pipe = data_pipe[1];
rw_ti->write_pipe = data_pipe[0];
rw_ti->pipe_size = pipe_size;
return NULL;
error:
exit(EXIT_FAILURE);
}
/* Bind a thread to a cpu */
static void bind_cpu(int cpu_num)
{
cpu_set_t mask;
CPU_ZERO(&mask);
CPU_SET(cpu_num, &mask);
/* bind my thread to cpu_num by assigning zero to the first argument */
if (sched_setaffinity(0, sizeof(mask), &mask) == -1)
pr_err("Could not set CPU#%d affinity\n", (int)cpu_num);
}
static void *rw_thread_main(void *thread_info)
{
ssize_t rlen, wlen;
ssize_t ret;
struct rw_thread_info *ts = (struct rw_thread_info *)thread_info;
bind_cpu(ts->cpu_num);
while (1) {
/* Wait for a read order of trace data by Host OS */
if (!global_run_operation) {
pthread_mutex_lock(&mutex_notify);
pthread_cond_wait(&cond_wakeup, &mutex_notify);
pthread_mutex_unlock(&mutex_notify);
}
if (global_sig_receive)
break;
/*
* Each thread read trace_pipe_raw of each cpu bounding the
* thread, so contention of multi-threads does not occur.
*/
rlen = splice(ts->in_fd, NULL, ts->read_pipe, NULL,
ts->pipe_size, SPLICE_F_MOVE | SPLICE_F_MORE);
if (rlen < 0) {
pr_err("Splice_read in rw-thread(%d)\n", ts->cpu_num);
goto error;
} else if (rlen == 0) {
/*
* If trace data do not exist or are unreadable not
* for exceeding the page size, splice_read returns
* NULL. Then, this waits for being filled the data in a
* ring-buffer.
*/
usleep(READ_WAIT_USEC);
pr_debug("Read retry(cpu:%d)\n", ts->cpu_num);
continue;
}
wlen = 0;
do {
ret = splice(ts->write_pipe, NULL, ts->out_fd, NULL,
rlen - wlen,
SPLICE_F_MOVE | SPLICE_F_MORE);
if (ret < 0) {
pr_err("Splice_write in rw-thread(%d)\n",
ts->cpu_num);
goto error;
} else if (ret == 0)
/*
* When host reader is not in time for reading
* trace data, guest will be stopped. This is
* because char dev in QEMU is not supported
* non-blocking mode. Then, writer might be
* sleep in that case.
* This sleep will be removed by supporting
* non-blocking mode.
*/
sleep(1);
wlen += ret;
} while (wlen < rlen);
}
return NULL;
error:
exit(EXIT_FAILURE);
}
pthread_t rw_thread_run(struct rw_thread_info *rw_ti)
{
int ret;
pthread_t rw_thread_per_cpu;
ret = pthread_create(&rw_thread_per_cpu, NULL, rw_thread_main, rw_ti);
if (ret != 0) {
pr_err("Could not create a rw thread(%d)\n", rw_ti->cpu_num);
exit(EXIT_FAILURE);
}
return rw_thread_per_cpu;
}