From f4874261049e3abdd481359d82cafa5068369ebd Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Red Hat)" Date: Tue, 29 Apr 2014 16:07:28 -0400 Subject: [PATCH] tracing: Break out of tracing_wait_pipe() before wait_pipe() is called When reading from trace_pipe, if tracing is off but nothing was read it should block. If something is read and tracing is off, then EOF is returned. If tracing is on and there's nothing to read, it will block. But because the check of whether tracing is off and something was read is done after the block on the pipe, it is hit or miss if the EOF is returned or not leading to inconsistent behavior. Signed-off-by: Steven Rostedt --- kernel/trace/trace.c | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index cb41e98cc64b..e058c6091e45 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -4237,15 +4237,6 @@ static int tracing_wait_pipe(struct file *filp) return -EAGAIN; } - mutex_unlock(&iter->mutex); - - iter->trace->wait_pipe(iter); - - mutex_lock(&iter->mutex); - - if (signal_pending(current)) - return -EINTR; - /* * We block until we read something and tracing is disabled. * We still block if tracing is disabled, but we have never @@ -4257,6 +4248,15 @@ static int tracing_wait_pipe(struct file *filp) */ if (!tracing_is_on() && iter->pos) break; + + mutex_unlock(&iter->mutex); + + iter->trace->wait_pipe(iter); + + mutex_lock(&iter->mutex); + + if (signal_pending(current)) + return -EINTR; } return 1; -- 2.39.2