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    SubjectRe: USB hangs
    Where is USB kmalloc'ing with GFP_KERNEL?  I thought we tracked all those
    down and eliminated them.

    Matt

    On Sun, Jan 11, 2004 at 12:07:17AM +0000, Alan Cox wrote:
    > With the various fixes people had been posting USB storage
    > writing was still hanging repeatedly when doing a 20Gb rsync
    > to usb-storage disks with a low memory system. Doing things
    > like while(true) sync() made it hang even more often.
    >
    > After a bit of digging the following seems to fix it
    >
    > Not sure if 2.6 needs this as well.
    >
    > The failure path seems to be
    >
    > ->scsi_done in the USB storage thread
    > issues a new command
    > causes USB to kmalloc GFP_KERNEL
    > causes a page out
    > queues a page out to the USB storage thread
    > Deadlock.
    >
    > Setting PF_MEMALLOC should stop the storage thread ever causing pageout
    > itself so deadlocking.
    >

    > --- drivers/usb/storage/usb.c~ 2004-01-09 02:06:35.000000000 +0000
    > +++ drivers/usb/storage/usb.c 2004-01-09 02:06:35.000000000 +0000
    > @@ -332,6 +332,8 @@
    >
    > /* set our name for identification purposes */
    > sprintf(current->comm, "usb-storage-%d", us->host_number);
    > +
    > + current->flags |= PF_MEMALLOC;
    >
    > unlock_kernel();
    >


    --
    Matthew Dharm Home: mdharm-usb@one-eyed-alien.net
    Maintainer, Linux USB Mass Storage Driver

    Your lips are twitching. You're playing Quake aren't you.
    -- Stef to Greg
    User Friendly, 8/11/1998
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