linux-kernel - Re: [PATCH 4/6] USB-BKL: Remove BKL use in uhci-debug

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Date:	Wed, 2 Jun 2010 09:47:46 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Arnd Bergmann <arnd@...db.de>
cc:	Greg KH <gregkh@...e.de>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	USB list <linux-usb@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	John Kacur <jkacur@...hat.com>,
	Andi Kleen <andi@...stfloor.org>,
	Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 4/6] USB-BKL: Remove BKL use in uhci-debug

On Tue, 1 Jun 2010, Arnd Bergmann wrote:

> From: Andi Kleen <ak@...ux.intel.com>
> 
> BKL was not really needed, just came from earlier push downs.

Yes.

> The only part that's a bit dodgy is the lseek function. Would
> need another lock or atomic access to fpos on 32bit?
> Better to have a libfs lseek

It doesn't matter.  Anyone who tries to do lseeks on this file 
from two different threads, simultaneously, deserves what they get.

> @@ -539,11 +534,11 @@ static loff_t uhci_debug_lseek(struct file *file, loff_t off, int whence)
>  		new = file->f_pos + off;
>  		break;
>  	}
> +
> +	/* XXX: Can size shrink? */
>  	if (new < 0 || new > up->size) {
> -		unlock_kernel();
>  		return -EINVAL;
>  	}
> -	unlock_kernel();
>  	return (file->f_pos = new);
>  }

This comment isn't needed; the size cannot change after the file has 
been opened.

Alan Stern

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