linux-kernel - Re: [PATCH] asm-generic: Use raw_local_irq_save/restore instead local_irq

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Message-ID: <4C4FBEDC.4000008@monstr.eu>
Date:	Wed, 28 Jul 2010 07:23:40 +0200
From:	Michal Simek <monstr@...str.eu>
To:	Mike Frysinger <vapier.adi@...il.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>, rostedt@...dmis.org,
	linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...e.hu,
	linux-arch@...r.kernel.org
Subject: Re: [PATCH] asm-generic: Use raw_local_irq_save/restore instead local_irq_save/restore

Mike Frysinger wrote:
> On Tue, Jul 27, 2010 at 19:18, Andrew Morton wrote:
>> On Mon, 26 Jul 2010 10:49:50 +0200 Michal Simek 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?
> 
> do you mean TRACE_IRQFLAGS_SUPPORT ?  Blackfin should ... my
> understanding was that arches just needed to implement asm/irqflags.h
> for it.

Blackin uses own include/asm/atomic.h implementation where shouldn't be 
a problem with irqflags tracer. Look at my second post.

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
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