Message-ID: <47C43F18.6060207@pobox.com>
Date: Tue, 26 Feb 2008 11:32:24 -0500
From: Jeff Garzik <jgarzik@pobox.com>
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To: Ingo Molnar <mingo@elte.hu>
CC: Thomas Gleixner <tglx@linutronix.de>,
       Andrew Morton <akpm@linux-foundation.org>,
       =?ISO-8859-1?Q?Bj=F6rn_Steinbrink?= <B.Steinbrink@gmx.de>,
       LKML <linux-kernel@vger.kernel.org>
Subject: Re: 2.6.24-git: kmap_atomic() WARN_ON()
References: <alpine.LFD.1.00.0802070054220.9204@apollo.tec.linutronix.de> <20080225195924.GA23176@atjola.homenet> <47C32043.6090809@pobox.com> <20080225124054.9b69e9f0.akpm@linux-foundation.org> <alpine.LFD.1.00.0802252242290.7583@apollo.tec.linutronix.de> <47C34CEA.7060307@pobox.com> <20080226083904.GC9857@elte.hu>
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Ingo Molnar wrote:
> * Jeff Garzik <jgarzik@pobox.com> wrote:
> 
>> +	unsigned long flags;
>> +
>> +	local_irq_save(flags);
> 
> hm, couldnt we attach the irq disabling to some spinlock, in a natural 
> way? Explicit flags fiddling is a PITA once we do things like threaded 
> irq handlers, -rt, etc.

Attaching the irq disabling to some spinlock is what would be 
artificial...  See the ahci.c patch earlier in this thread.  It is taken 
without spin_lock_irqsave() in the interrupt handler, and there is no 
reason to disable interrupts for the entirety of the interrupt handler 
run -- only the part where we call kmap.

This is only being done to satisfy kmap_atomic's requirements, not libata's.

I could add a "kmap lock" but that just seems silly.

	Jeff


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