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Message-ID: <3D4FA924.3030601@evision.ag>
Date: Tue, 06 Aug 2002 12:47:00 +0200
From: Marcin Dalecki <dalecki@evision.ag>
Reply-To: martin@dalecki.de
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To: Jens Axboe <axboe@suse.de>
CC: Petr Vandrovec <VANDROVE@vc.cvut.cz>, linux-kernel@vger.kernel.org,
       torvalds@transmeta.com
Subject: Re: [PATCH] 2.5.30 IDE 113
References: <13AC5F92253@vcnet.vc.cvut.cz> <20020806104414.GC1132@suse.de>
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Uz.ytkownik Jens Axboe napisa?:
> On Tue, Aug 06 2002, Petr Vandrovec wrote:
> 
>>>After all ide_raw_taskfile only gets used for REQ_SPECIAL request
>>>types. This does *not* contain normal data request from block IO.
>>>As of master slave issues - well we have the data pre allocated per
>>>device not per channel! If q->request_fn would properly return the
>>>error count instead of void, we could even get rid ot the
>>>checking for rq->errors after finishment... But well that's
>>>entierly different story.
>>
>>For example do_cmd_ioctl() invokes ide_raw_taskfile, without any locking.
>>Two programs, both issuing HDIO_DRIVE_CMD at same time, will compete
>>over one drive->srequest struct: you'll get same drive->srequest structure
>>submitted twice to blk_insert_request (hm, Jens, will this trigger
>>BUG, or will this just damage request list?).
> 
> 
> Just silently damage request list. We _could_ easily add code to detect
> this, but it's not been a problem in the past so not worth looking for.
> 
> AFAICS, Petr is completely right wrt this race.

For the ioctl case yes. But:

1. We already look for blk_queue_empty there.
2. We have just to deal properly with the queue plugging there
to close it up.
3. I will just add spin locking on ide_lock to maintain that no two
ioctl can overlapp at all.

OK?


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