Re: PR/42455

[Christoph Egger <Christoph_Egger%gmx.de@localhost>]

The following reply was made to PR kern/42455; it has been noted by GNATS.

From: Christoph Egger <Christoph_Egger%gmx.de@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: kern-bug-people%netbsd.org@localhost, gnats-admin%netbsd.org@localhost, 
 netbsd-bugs%netbsd.org@localhost
Subject: Re: PR/42455
Date: Thu, 10 Mar 2011 11:10:24 +0100

 I want to mention this OpenBSD commit log as it gives an idea where
 to start to search in the driver: Handling of empty rings.
 
 Christoph
 
 
 http://article.gmane.org/gmane.os.openbsd.cvs/102392
 
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 CVSROOT:       /cvs
 Module name:   src
 Changes by:    claudio <at> cvs.openbsd.org    2010/12/21 07:00:43
 
 Modified files:
        sys/kern       : uipc_mbuf.c
 
 Log message:
 Ugly workaround in nmbclust_update(). Additionally to setting the limit
 also modify the hiwat mark. This was done in pool_sethardlimit() until
 rev. 1.99. Without this the mbuf cluster pool may return free pages too
 quickly with the result that m_clget() may fail while populating DMA
 rings. Seems to fix some hangs seen on MCLGETI() interfaces on i386
 e.g. PR 6524. A proper fix is to make all drivers handle empty rings
 but that will take a while to implement.  With and OK mikeb@
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