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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>
This commit is contained in:
Steven Rostedt 2008-05-12 21:20:58 +02:00 committed by Thomas Gleixner
parent 845279972f
commit 2dc8f09571
1 changed files with 4 additions and 0 deletions
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4
kernel/trace/trace.c
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@ -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: