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From: Keith Owens <kaos@ocs.com.au>
To: Zwane Mwaikambo <zwane@linuxpower.ca>
Cc: linux-kernel@vger.kernel.org
Subject: Re: 2.6.7-rc2 mismatched preempt count in arch/i386/kernel/irq.c 
In-reply-to: Your message of "Mon, 31 May 2004 03:50:19 -0400."
             <Pine.LNX.4.58.0405310347140.1794@montezuma.fsmlabs.com> 
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Date: Mon, 31 May 2004 17:56:51 +1000
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On Mon, 31 May 2004 03:50:19 -0400 (EDT), 
Zwane Mwaikambo <zwane@linuxpower.ca> wrote:
>On Mon, 31 May 2004, Keith Owens wrote:
>
>> 2.6.7-rc2 (and earlier) arch/i386/kernel/irq.c::do_IRQ() calls
>> irq_exit() which expands into preempt_enable_no_resched(), amongst
>> others.  With CONFIG_PREEMPT=y, preempt_enable_no_resched() does
>> dec_preempt_count().  Where is the corresponding inc_preempt_count?
>> AFAICT the use of preempt_enable_no_resched() is unbalanced.
>
>I believe IRQ_EXIT_OFFSET takes care of that;
>
>#define IRQ_EXIT_OFFSET (HARDIRQ_OFFSET-1)
>
>#define irq_exit()							\
>do {									\
>		preempt_count() -= IRQ_EXIT_OFFSET;			\
>		if (!in_interrupt() && softirq_pending(smp_processor_id())) \
>			do_softirq();					\
>		preempt_enable_no_resched();				\
>} while (0)

How ugly ....