From: Steven Rostedt <rostedt@goodmis.org>
Date: Mon, 12 May 2008 19:20:58 +0000 (+0200)
Subject: ftrace: trace_pipe implement NONBLOCK
X-Git-Tag: v2.6.27-rc1~1102^2^2~1^2~54
X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=2dc8f09571a61d9cb3dc47bba6608689dfe15d16;p=linux-2.6-omap-h63xx.git

ftrace: trace_pipe implement NONBLOCK

This patch implements "NONBLOCK" for trace_pipe. If the trace_pipe is opened
with O_NONBLOCK, then the trace_pipe read will not block when buffer is empty.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 2af940433e9..3b4eaf36ed5 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2233,6 +2233,10 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
 	start = 0;
 
 	while (trace_empty(iter)) {
+
+		if ((filp->f_flags & O_NONBLOCK))
+			return -EAGAIN;
+
 		/*
 		 * This is a make-shift waitqueue. The reason we don't use
 		 * an actual wait queue is because: