From owner-cvs-all  Sat Mar 15  1:12:54 2003
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Date: Sat, 15 Mar 2003 01:12:44 -0800
From: David Schultz <das@FreeBSD.ORG>
To: David Xu <davidxu@FreeBSD.ORG>
Cc: John Baldwin <jhb@FreeBSD.ORG>, cvs-all@FreeBSD.ORG,
	cvs-src@FreeBSD.ORG, src-committers@FreeBSD.ORG
Subject: Re: cvs commit: src/lib/libpthread/thread thr_rwlock.c
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Mail-Followup-To: David Xu <davidxu@FreeBSD.org>,
	John Baldwin <jhb@FreeBSD.org>, cvs-all@FreeBSD.org,
	cvs-src@FreeBSD.org, src-committers@FreeBSD.org
References: <200303150347.h2F3lLjK069888@freefall.freebsd.org>
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Thus spake David Xu <davidxu@FreeBSD.org>:
> This design prevents a thread to get a reader lock recursively when
> there is a writter blocked on a rwlock.

You're right in that the standard blesses the practice of a reader
recursing on a lock.  Glancing briefly at the code, it looks like
we presently deadlock if a writer is waiting.  However, the fix is
not so trivial.  Writers *must* be given priority over readers
within a bounded amount of time or they will be starved.  Consider
what happens when you have a neverending stream of readers.

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