Re: USB hangs

[Matthew Dharm <mdharm-kernel@one-eyed-alien.net>]

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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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