From: Ingo Molnar <mingo@elte.hu>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>,
linux-kernel@vger.kernel.org,
Martin Schwidefsky <schwidefsky@de.ibm.com>
Subject: Re: ftrace: preemptoff selftest not working
Date: Tue, 18 Nov 2008 14:52:21 +0100 [thread overview]
Message-ID: <20081118135221.GE31146@elte.hu> (raw)
In-Reply-To: <alpine.DEB.1.10.0811180826510.15003@gandalf.stny.rr.com>
* Steven Rostedt <rostedt@goodmis.org> wrote:
> > Hence the trace buffer will be empty. The patch below makes the
> > selftests working for me, since then they run in preemptible
> > context. But it is ugly and I'm not proposing it for upstream ;)
> >
> > Just wanted to make you aware that there is a bug.
>
> Yep, this might be a better answer than what I put into linux-tip
> (and my git repo).
>
> See:
>
> ftrace: force pass of preemptoff selftest
>
> The cause of the bug was the conversion of the BKL back to a
> spinlock, and making it non preempt. The initcall code is called
> with the BKL applied which now means it can not preempt. This breaks
> the preempt tracer selftest.
>
> My solution was to just force a pass if this is detected. Perhaps
> moving the test might be better.
it would be better to just drop the BKL in that selftest. (or in all
selftests - an elevated preempt count will skew a number of things)
Ingo
next prev parent reply other threads:[~2008-11-18 13:52 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-11-18 12:54 ftrace: preemptoff selftest not working Heiko Carstens
2008-11-18 13:48 ` Ingo Molnar
2008-11-18 13:49 ` Steven Rostedt
2008-11-18 13:52 ` Ingo Molnar [this message]
2008-11-18 14:32 ` Steven Rostedt
2008-11-18 14:47 ` Ingo Molnar
2008-11-18 17:06 ` Heiko Carstens
2008-11-18 17:21 ` Steven Rostedt
2008-11-18 20:55 ` Ingo Molnar
2008-11-19 9:02 ` Ingo Molnar
2008-11-19 9:23 ` Heiko Carstens
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