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From: "Keith Arner" <vornum@gmail.com>
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To: "Attilio Rao" <attilio@freebsd.org>
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Cc: freebsd-smp@freebsd.org
Subject: Re: INP_INFO_WLOCK(&tcbinfo) bottleneck
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On 3/1/07, Attilio Rao <attilio@freebsd.org> wrote:
>
>
> Currently, the main problem for this is that somewhere (TM) there
> mutex gets recursed and recursion is not handled alredy for rwlocks,
> so kernel starts panicing.
>
> Patch for recursion in rwlock is not trivial, but there are ongoing
> discussions on it.
>

Well, even if the INP_INFO_[RW]LOCK macros were changed to use
shared/exclusive locks rather than a mutex, and the sx locks were fixed
to be taken recursively, I'm not sure that would really do the trick for
parallelism.  In tcp_input(), the code is using INP_INFO_WLOCK(), to
take an exclusive lock, so only one thread would be able to be in the
TCP input code path anyway.

Keith