Message-ID: <431E497A.4080303@rtr.ca>
Date: Tue, 06 Sep 2005 21:59:22 -0400
From: Mark Lord <lkml@rtr.ca>
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To: Daniel Phillips <phillips@istop.com>
Cc: Giridhar Pemmasani <giri@lmc.cs.sunysb.edu>, linux-kernel@vger.kernel.org,
       Andi Kleen <ak@suse.de>
Subject: Re: RFC: i386: kill !4KSTACKS
References: <20050904145129.53730.qmail@web50202.mail.yahoo.com> <58d0dbf10509061005358dce91@mail.gmail.com> <dfkjav$lmd$1@sea.gmane.org> <200509061819.45567.phillips@istop.com>
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Daniel Phillips wrote:
> There are only two stacks involved, the normal kernel stack and your new ndis 
> stack.  You save ESP of the kernel stack at the base of the ndis stack.  When 
> the Windows code calls your api, you get the ndis ESP, load the kernel ESP 
> from the base of the ndis stack, push the ndis ESP so you can get back to the 
> ndis code later, and continue on your merry way.

With CONFIG_PREEMPT, this will still cause trouble due to lack
of "current" task info on the NDIS stack.

One option is to copy (duplicate) the bottom-of-stack info when
switching to the NDIS stack.

Another option is to stick a Mutex around any use of the NDIS stack
when calling into the foreign driver (might be done like this already??),
which will prevent PREEMPTion during the call.

Cheers
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