Commit 9ff4b974 authored by Pekka Paalanen's avatar Pekka Paalanen Committed by Ingo Molnar
Browse files

tracing/ftrace: fix pipe breaking 



This patch fixes a bug which break the pipe when the seq is empty.

Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 2c4f035f

kernel/trace/trace.c

+8 −2
Original line number Diff line number Diff line
@@ -2439,7 +2439,6 @@ tracing_read_pipe(struct file *filp, char __user *ubuf, 
	sret = trace_seq_to_user(&iter->seq, ubuf, cnt);

	if (sret != -EBUSY)

		return sret;

	sret = 0;



	trace_seq_reset(&iter->seq);
@@ -2450,6 +2449,8 @@ tracing_read_pipe(struct file *filp, char __user *ubuf, 
			goto out;

	}



waitagain:

	sret = 0;

	while (trace_empty(iter)) {



		if ((filp->f_flags & O_NONBLOCK)) {
@@ -2556,8 +2557,13 @@ tracing_read_pipe(struct file *filp, char __user *ubuf, 
	sret = trace_seq_to_user(&iter->seq, ubuf, cnt);

	if (iter->seq.readpos >= iter->seq.len)

		trace_seq_reset(&iter->seq);



	/*

	 * If there was nothing to send to user, inspite of consuming trace

	 * entries, go back to wait for more entries.

	 */

	if (sret == -EBUSY)

		sret = 0;

		goto waitagain;



out:

	mutex_unlock(&trace_types_lock);