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Message-ID: <c62985530810280835k66d3ab87qd1783a0135228174@mail.gmail.com>
Date: Tue, 28 Oct 2008 16:35:11 +0100
From: "=?ISO-8859-1?Q?Fr=E9d=E9ric_Weisbecker?=" <fweisbec@gmail.com>
To: "Steven Rostedt" <rostedt@goodmis.org>
Subject: Re: [PATCH] ftrace: fix current_tracer error return
Cc: "Linux Kernel" <linux-kernel@vger.kernel.org>,
       "Ingo Molnar" <mingo@elte.hu>,
       "Andrew Morton" <akpm@linux-foundation.org>,
       "Linus Torvalds" <torvalds@linux-foundation.org>
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2008/10/28 Steven Rostedt <rostedt@goodmis.org>:
>
> The commit (in linux-tip) c2931e05ec5965597cbfb79ad332d4a29aeceb23
>  ( ftrace: return an error when setting a nonexistent tracer )
> added useful code that would error when a bad tracer was written into
> the current_tracer file.
>
> But this had a bug if the amount written was more than the amount read by
> that code. The first iteration would set the tracer correctly, but since
> it did not consume the rest of what was written (usually whitespace), the
> userspace utility would continue to write what was not consumed. This
> second iteration would fail to find a tracer and return -EINVAL. Funny
> thing is that the tracer would have already been set.
>
> This patch just consumes all the data that is written to the file.
>
>
> Signed-off-by: Steven Rostedt <srostedt@redhat.com>



An that corrects the bug when I failed to assign the sched_switch tracer.
Thanks Steven!

Tested-by: Frederic Weisbecker <fweisbec@gmail.com>