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From: Nick Piggin <piggin@cyberone.com.au>
To: Jens Axboe <axboe@suse.de>
Cc: Linux Kernel <linux-kernel@vger.kernel.org>,
	Linus Torvalds <torvalds@osdl.org>
Subject: Re: AS spin lock bugs
Date: Thu, 13 Nov 2003 21:52:22 +1100	[thread overview]
Message-ID: <3FB36266.7050103@cyberone.com.au> (raw)
In-Reply-To: <20031113103823.GB4441@suse.de>



Jens Axboe wrote:

>Hi,
>
>Was looking at io tracking for cfq, and I think I found some spin lock
>bugs in current as (current BK). as_update_iohist() runs from
>add_request which is typically in process context. It could be run with
>interrupts disabled though, either driver private stuff or using the
>generic block layer tagging.
>
>Anyways, as_update_iohist() grabs aic->lock without disabling
>interrupts, while as_completed_request() typically runs at interrupt
>time and grabs the same lock. Deadlock.
>
>To be safe, both need to use the flags saving lock variants.
>

Hi Jens,
I was hoping everything ran under the queue lock which should always
have interrupts off on the local CPU. The lock in question is to prevent
a as_completed_request on one queue from racing with as_update_iohist
on another. Each would be on a different CPU.

Maybe I'm wrong, did you actually see misbehaviour?



  reply	other threads:[~2003-11-13 10:55 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2003-11-13 10:38 AS spin lock bugs Jens Axboe
2003-11-13 10:52 ` Nick Piggin [this message]
2003-11-13 10:59   ` Jens Axboe
2003-11-13 10:52 ` Jens Axboe
2003-11-13 10:59   ` Nick Piggin
2003-11-13 11:01     ` Jens Axboe
2003-11-13 11:10       ` Jens Axboe
2003-11-13 11:16         ` Nick Piggin

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