From: Michal Simek <monstr@monstr.eu>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: rostedt@goodmis.org, linux-kernel@vger.kernel.org,
tglx@linutronix.de, mingo@elte.hu, linux-arch@vger.kernel.org
Subject: Re: [PATCH] asm-generic: Use raw_local_irq_save/restore instead local_irq_save/restore
Date: Wed, 28 Jul 2010 07:20:43 +0200 [thread overview]
Message-ID: <4C4FBE2B.6030606@monstr.eu> (raw)
In-Reply-To: <20100727161819.cf6feab1.akpm@linux-foundation.org>
Andrew Morton wrote:
> On Mon, 26 Jul 2010 10:49:50 +0200
> Michal Simek <monstr@monstr.eu> wrote:
>
>> start/stop_critical_timing function for preemptirqsoff, preemptoff
>> and irqsoff tracers contains atomic_inc and atomic_dec operations.
>>
>> Atomic operations used local_irq_save/restore macros to ensure
>> atomic access but they are traced by the same function which is causing
>> recursion problem.
>>
>> The reason is when these tracers are turn ON then local_irq_save/restore
>> macros are changed in include/linux/irqflags.h to call trace_hardirqs_on/off
>> which call start/stop_critical_timing.
>>
>> Microblaze was affected because use generic atomic implementation.
>
> Seems that this will also affect blackfin, mn10300 and score. I guess
> they aren't supporting tracing yet?
If they uses asm-generic/atomic.h, then yes. It seems to me that
Blackfin uses own asm/atomic.h. nm10300 and score are the same case as
Microblaze.
In include/linux/irqflags.h is written this commentary.
/*
* The local_irq_*() APIs are equal to the raw_local_irq*()
* if !TRACE_IRQFLAGS.
*/
If architecture doesn't enable TRACE_IRQFLAGS then there is no
difference in behavior. If yes and use asm-generic/atomic.h code, then
IRQFLAG tracer freeze because it is traced part of irqsoff tracer
because of recursion as is describe in patch description.
>
>> Signed-off-by: Michal Simek <monstr@monstr.eu>
>> Acked-by: Steven Rostedt <rostedt@goodmis.org>
>> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
>
> hm, I wonder how my signoff got there. Doesn't matter.
http://lkml.org/lkml/2010/5/26/364
Michal
--
Michal Simek, Ing. (M.Eng)
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel 2.6 Microblaze Linux - http://www.monstr.eu/fdt/
Microblaze U-BOOT custodian
next prev parent reply other threads:[~2010-07-28 5:24 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1274863724-14906-1-git-send-email-monstr@monstr.eu>
[not found] ` <1274863724-14906-2-git-send-email-monstr@monstr.eu>
2010-05-26 14:42 ` [PATCH] asm-generic: Use raw_local_irq_save/restore instead local_irq_save/restore Steven Rostedt
2010-05-26 17:08 ` Andrew Morton
2010-05-26 17:11 ` Steven Rostedt
2010-05-27 7:14 ` Michal Simek
2010-05-27 9:11 ` Yong Zhang
2010-07-26 8:49 ` Michal Simek
2010-07-27 23:18 ` Andrew Morton
2010-07-27 23:54 ` Mike Frysinger
2010-07-28 5:23 ` Michal Simek
2010-07-28 5:20 ` Michal Simek [this message]
2010-07-28 5:35 ` Mike Frysinger
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