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

Source file repositories/reference/linux-study-clean/tools/virtio/virtio-trace/trace-agent-rw.c

File Facts

System
Linux kernel
Corpus path
tools/virtio/virtio-trace/trace-agent-rw.c
Extension
.c
Size
4398 bytes
Lines
191
Domain
Support Tooling And Documentation
Bucket
tools
Inferred role
Support Tooling And Documentation: implementation source
Status
source implementation candidate

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

Detected Declarations

Annotated Snippet

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,

Annotation

Implementation Notes