Messages in this thread | | | Date | Tue, 6 Aug 2002 13:03:54 +0200 | From | Jens Axboe <> | Subject | Re: [PATCH] 2.5.30 IDE 113 |
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On Tue, Aug 06 2002, Marcin Dalecki wrote: > 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.
I don't know what you mean here. Clearly this is an ide problem. If you have a statically allocated request, you _must_ serialize that yourself.
> 3. I will just add spin locking on ide_lock to maintain that no two > ioctl can overlapp at all.
Agrh god no. So you'll spin waiting for the ioctl to complete?
From ide_raw_taskfile(), the right way to do it is:
struct request *rq = blk_get_request(...);
This gets _everything_ right.
BTW, _glad to see you got rid of the horrible insert-and-execute stuff in ide_raw_taskfile(). That was a layering violation.
> OK?
Not likely :-)
-- Jens Axboe
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