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Commit b627344f authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt
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tracing: Fix read blocking on trace_pipe_raw 



If the ring buffer is empty, a read to trace_pipe_raw wont block.
The tracing code has the infrastructure to wake up waiting readers,
but the trace_pipe_raw doesn't take advantage of that.

When a read is done to trace_pipe_raw without the O_NONBLOCK flag
set, have the read block until there's data in the requested buffer.

Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent cc60cdc9

kernel/trace/trace.c

+15 −3
Original line number Diff line number Diff line
@@ -4389,6 +4389,7 @@ static int tracing_buffers_open(struct inode *inode, struct file *filp) 


	info->iter.tr		= tr;

	info->iter.cpu_file	= tc->cpu;

	info->iter.trace	= tr->current_trace;

	info->spare		= NULL;

	/* Force reading ring buffer for first read */

	info->read		= (unsigned int)-1;
@@ -4428,14 +4429,25 @@ tracing_buffers_read(struct file *filp, char __user *ubuf, 
	if (info->read < PAGE_SIZE)

		goto read;



 again:

	trace_access_lock(iter->cpu_file);

	ret = ring_buffer_read_page(iter->tr->buffer,

				    &info->spare,

				    count,

				    iter->cpu_file, 0);

	trace_access_unlock(iter->cpu_file);

	if (ret < 0)



	if (ret < 0) {

		if (trace_empty(iter)) {

			if ((filp->f_flags & O_NONBLOCK))

				return -EAGAIN;

			iter->trace->wait_pipe(iter);

			if (signal_pending(current))

				return -EINTR;

			goto again;

		}

		return 0;

	}



	info->read = 0;
@@ -4616,7 +4628,7 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos, 
			ret = -EAGAIN;

			goto out;

		}

		default_wait_pipe(iter);

		iter->trace->wait_pipe(iter);

		if (signal_pending(current)) {

			ret = -EINTR;

			goto out;