Re: PR/42455

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

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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