From: javi.merino@arm•com (Javi Merino)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v2] ARM: pl330: Fix a race condition
Date: Sun, 11 Dec 2011 17:42:41 +0000 [thread overview]
Message-ID: <4EE4EB91.6020508@arm.com> (raw)
In-Reply-To: <CAJe_ZhcF7nMvnWxfpSROtq=8SYqG1o1TyfWty79eGM0oqntNsg@mail.gmail.com>
On 11/12/11 17:10, Jassi Brar wrote:
> On 11 December 2011 20:39, Javi Merino <javi.merino@arm•com> wrote:
>>>>
>>>> What about properly tracking what we have sent to the DMA? Something
>>>> like the following (warning *ugly* and untested code ahead, may eat your
>>>> kitten):
>>>>
>>> Yeah, this is like I said 'marker' method. Though we can clean it up a bit.
>>> 1) Pack req_running and lstenq together. Make lsteng return invalid value
>>> should there be no buff programmed, otherwise 0 or 1.
>>
>> This can lead to starvation. If lstenq is -1 when the DMA hasn't been
>> programmed yet, in _trigger() you don't know which buffer is the
>> "oldest", so you may end up always starting the new buffer and
>> forgetting about the other one. lstenq as it is right now prevents that.
>>
> Sorry I don't understand. If lstenq is -1 that means there's no req programmed
> so trigger need not do anything. I didn't say we don't need to do anything else.
Currently lstenq tracks the last request that pl330_submit_req() has
enqueued. I think we should add a req_running (or any other name) that
tracks what _trigger() has sent to the DMA. If we pack them together we
lose some information and I don't see a way of packing them safely.
> Though it's just an idea I haven't implemented and it may not work out.
I was trying to implement it and got stuck in _trigger() thinking "ok,
so which buffer am I supposed to trigger now..."
> Just please give it a try if you can. Thanks.
I have a patch that seems to be working. Let me test it a little bit
more and I'll send it to the list.
Cheers,
Javi
next prev parent reply other threads:[~2011-12-11 17:42 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-19 17:11 [PATCH] ARM: pl330: Fix a race condition Javi Merino
2011-09-19 18:07 ` Jassi Brar
2011-09-20 13:36 ` Javi Merino
2011-10-05 12:57 ` Javi Merino
2011-10-06 9:10 ` [PATCH v2] " Javi Merino
2011-11-05 19:05 ` Thomas Abraham
2011-11-07 10:48 ` Javi Merino
2011-11-07 11:03 ` Thomas Abraham
2011-11-28 8:23 ` Boojin Kim
2011-11-28 16:36 ` Javi Merino
2011-11-29 3:41 ` Boojin Kim
2011-11-29 9:53 ` Javi Merino
2011-11-29 10:37 ` Jassi Brar
2011-12-07 7:52 ` Kukjin Kim
2011-12-07 10:01 ` Javi Merino
2011-12-07 20:54 ` Javi Merino
2011-12-09 11:58 ` Javi Merino
2011-12-09 13:04 ` Jassi Brar
2011-12-09 13:41 ` Javi Merino
2011-12-09 14:15 ` Jassi Brar
2011-12-09 14:52 ` Javi Merino
2011-12-09 16:50 ` Jassi Brar
2011-12-09 19:50 ` Javi Merino
2011-12-11 10:51 ` Jassi Brar
2011-12-11 15:09 ` Javi Merino
2011-12-11 17:10 ` Jassi Brar
2011-12-11 17:42 ` Javi Merino [this message]
2011-12-11 19:27 ` [PATCH] ARM: PL330: Fix driver freeze Javi Merino
2011-12-15 17:48 ` Javi Merino
2011-12-16 9:01 ` Tushar Behera
2011-12-16 6:27 ` Jassi Brar
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