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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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