From 9ff4b9744c187cae58c3774361ea090addbc4130 Mon Sep 17 00:00:00 2001 From: Pekka Paalanen Date: Mon, 29 Sep 2008 20:23:48 +0200 Subject: [PATCH] tracing/ftrace: fix pipe breaking This patch fixes a bug which break the pipe when the seq is empty. Signed-off-by: Frederic Weisbecker Signed-off-by: Ingo Molnar --- kernel/trace/trace.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index b38a4bb40548..6a1c76bb56ba 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -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); -- GitLab