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Message-ID: <39FF20F7.E9E15008@mvista.com>
Date: Tue, 31 Oct 2000 11:43:51 -0800
From: George Anzinger <george@mvista.com>
Organization: Monta Vista Software
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To: Alan Cox <alan@lxorguk.ukuu.org.uk>
CC: "linux-kernel@vger.redhat.com" <linux-kernel@vger.kernel.org>
Subject: Re: Locking question, is this cool?
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Alan Cox wrote:
> 
> > At line 1073 of ../drivers/char/i2lib.c (2.4.0-test9) we find:
> >
> > WRITE_LOCK_IRQSAVE(...
> >
> > this is followed by:
> >
> > COPY_FROM_USER(...
> >
> > It seems to me that this could result in a page fault with interrupts
> > off.  Is this ok?
> 
> It wont do what you want - it'll re-enable irqs and may then deadlock. It might
> need to copy the buffer to a temporary space then take the lock >
> -
I suspected as much.  I see the same error (bug?) at line 978 of
../drivers/char/riotty.c

Seems like a common problem.

george
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