Re: duplicate read/write locks in net/pfil.c and netinet/ip_fw2.c

From: Luigi Rizzo (rizzo_at_icir.org)
Date: 08/18/05

  • Next message: John Baldwin: "Re: Special schedulers, one CPU only kernel, one only userland" 
    Date: Thu, 18 Aug 2005 07:31:24 -0700
To: Stephan Uphoff <ups@tree.com>

    On Thu, Aug 18, 2005 at 10:18:33AM -0400, Stephan Uphoff wrote:
    > On Thu, 2005-08-18 at 03:57, Luigi Rizzo wrote:
    ...
    > > In fact i don't understand why you consider spinning and sleeping
    > > on a mutex two different things.
    >
    > The major difference between sleeping (cv_wait,msleep,..) and blocking
    > on a mutex is priority inheritance.
    > If you need to be able to use (non-spin) mutexes while holding a
    > [R|W]LOCK and use a [R|W]LOCK while holding a (non-spin) mutex then you
    > need to implement priority inheritance for [R|W]LOCKs.

    is that required (in FreeBSD, i mean) for algorithmic
    correctness or just for performance ?

            cheers
            luigi
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