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SubjectRe: audio cd writing causes massive swap and crash
On Thu, Jul 22 2004, Ed Sweetman wrote:
> Martin Schlemmer wrote:
> >On Thu, 2004-07-22 at 14:54, Jens Axboe wrote:
> >
> >
> >>On Thu, Jul 22 2004, Ed Sweetman wrote:
> >>
> >>
> >>>I've had other people test writing. It appears that scsi-emu is not
> >>>effected by this memory leak when writing audio cds. So it would appear
> >>>that ide-cd along with any of the dependent ide source files is the
> >>>culprit. But I cannot find anywhere in ide-cd that is apparent to being
> >>>a mem leak. There are various conditions in ide_do_drive_cmd that state
> >>>that the cdrom driver has to be very careful about handling but without
> >>>intimate knowledge of the driver, I can't be sure that it's sufficiently
> >>>handling those situations.
> >>>
> >>>Surprisingly, it's very hard to find anyone who's used the native atapi
> >>>mode to write an audio cd in 2.6. Which is partly why this problem
> >>>hasn't generated more mail traffic here I would guess.
> >>>
> >>>
> >>That's not true, lots of people use it. But, oddly, the leak isn't
> >>reproducable on any machine I've tested.
> >>
> >>
> >
> >I seem to remember he noted a patch about dma during audio writing,
> >and his 'testing' if it might be the cause was to just disable dma
> >on the drive ...
> >
> >
> The patch is now part of vanilla 2.6. It was an audio dma api that was
> a workaround for the broken dma api that only allows ide commands
> 512bytes long. Schilling mentioned something about this in an earlier
> lkml posting around january.
> I've asked some other people in an irc channel to test out the problem.
> Basically You need to be using the native atapi method for recording
> audio. Also, it appears that the mem leak is just what happens to some
> people, other people like some of those who tested in the irc channel
> experienced random program sigsevs and no mem leak at all. It would
> appear from this that what may be happening is the cdrom ide module is
> mangling a pointer and either can't free it due to it possibly randomly
> pointing to null or cause crashes due to it randomly pointing to other
> anonymous/shared memory regions as kfree is called. That's obviously
> just a guess. But some sort of memory mangling is apparently
> happening. This is not just happening on my computer.
> My drive is using udma33 and not mdma so maybe that makes the problem
> occur more quickly. I disabled dma to test it writing the old way but
> it appears to be occuring in ide-cd or somewhere between cdrom.o and the
> block device layer. ide-scsi people dont have the problem at all
> apparently.

Does turning on all the debug options (memory related, mostly) reveal
anything interesting?

Jens Axboe

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