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Date: Thu, 11 Dec 2003 16:36:49 -0700
From: Scott Long <scottl@freebsd.org>
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To: Fabien THOMAS <fabien.thomas@netasq.com>
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cc: freebsd-scsi@freebsd.org
Subject: Re: asr driver with INVARIANT
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Fabien THOMAS wrote:
> When compiled with INVARIANT the driver failed in debugger because the
> memory flags is M_WAITOK.
> 
> Is it really necessary to use M_WAITOK here ?
> 
> fabien
> 
> 

Allocating any memory from within the strategy() path is generally a 
really bad idea no matter what.  However, changing this to M_NOWAIT
means that a memory shortage will cause the I/O to fail.  What happens
if the failed I/O request originated from the vm system trying to push
pages to the swap partition in order to create more free memory?

The better solution is to pre-allocate all resources needed in this
path.  Unfortunately, the asr driver is maintainerless.  I and many
others on this list would be happy to review any patches that you
come up with to solve this problem.

Scott