linux-kernel - Re: [PATCH -rt] rt-slab: fix cpu inconsistency case

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Message-ID: <47E818E4.2050602@ct.jp.nec.com>
Date:	Mon, 24 Mar 2008 14:11:00 -0700
From:	Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org
Subject: Re: [PATCH -rt] rt-slab: fix cpu inconsistency case

Steven Rostedt wrote:
> On Mon, 24 Mar 2008, Steven Rostedt wrote:
> 
>> On Fri, 21 Mar 2008, Hiroshi Shimamoto wrote:
>>>> Is this a bug in mainline? The !PREEMPT_RT case should be as close to
>>>> mainline as possible, with no actual changes in object code. If this is
>>>> not the case, then we need to fix that.
>>> No, this issue is in -rt only.
>>>
>> Hi Hiroshi,
>>
>> Thanks again for reporting this. I took a deeper look into this today and
>> came to the conclusion that we need to get rid of both
>> slab_irq_disable_nort and slab_irq_disable_rt, and simply use
>> slab_irq_disable ;-)
>>
>> This is what you patch indirectly does. I'll write up another patch to fix
>> this.
>>
> 
> Actually, I'm going to take your patch.
> 
> Seems that the reason Ingo did the two separate, is that the functions
> called also call the slab_irq_save, which will retake the locks in
> PREEMPT_RT. If we don't release the lock, then we can deadlock.
> 

OK, actually, I had a interest in your rework :-)

thanks,
Hiroshi Shimamoto
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