From: Michal Schmidt <xschmi00@stud.feec.vutbr.cz>
To: "Nikita V. Youshchenko" <yoush@cs.msu.su>
Cc: linux-kernel@vger.kernel.org
Subject: Re: CONFIG_PREEMPT x86 assembly question
Date: Mon, 22 Nov 2004 23:10:39 +0100 [thread overview]
Message-ID: <41A263DF.2040907@stud.feec.vutbr.cz> (raw)
In-Reply-To: <200411201746.44804@sercond.localdomain>
Nikita V. Youshchenko wrote:
> In arch/i386/kernel/entry.S
>
> ...
> ENTRY(resume_kernel)
> cmpl $0,TI_preempt_count(%ebp) # non-zero preempt_count ?
> jnz restore_all
> need_resched:
> movl TI_flags(%ebp), %ecx # need_resched set ?
> testb $_TIF_NEED_RESCHED, %cl
> jz restore_all
> testl $IF_MASK,EFLAGS(%esp) # interrupts off (exception path) ?
> jz restore_all
> movl $PREEMPT_ACTIVE,TI_preempt_count(%ebp)
> sti
> call schedule
> movl $0,TI_preempt_count(%ebp)
> cli
> jmp need_resched
> #endif
> ...
>
> Why, after return from schedule(), first 0 is written to
> TI_preempt_count(%ebp), and only then interrupts are disabled?
> Wht not the reverse order?
>
It's already reversed in linux-2.6.10-rc2:
...
call schedule
cli
movl $0,TI_preempt_count(%ebp)
jmp need_resched
Michal
prev parent reply other threads:[~2004-11-22 22:15 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-11-20 14:43 CONFIG_PREEMPT x86 assembly question Nikita V. Youshchenko
2004-11-22 22:10 ` Michal Schmidt [this message]
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