From owner-freebsd-hackers  Sun Jun 23 13:33: 4 2002
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Date: Sun, 23 Jun 2002 13:32:31 -0700 (PDT)
From: Matthew Dillon <dillon@apollo.backplane.com>
Message-Id: <200206232032.g5NKWVZW063483@apollo.backplane.com>
To: Alfred Perlstein <bright@mu.org>
Cc: freebsd-hackers@FreeBSD.ORG,
	Julian Elischer <julian@elischer.org>, Alan Cox <alc@cs.rice.edu>,
	Tor.Egge@cvsup.no.freebsd.org
Subject: Re: Bug in wakeup() (stable and current) ?
References: <200206232014.g5NKE5x3058562@apollo.backplane.com> <20020623201933.GM53232@elvis.mu.org>
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:I'm pretty sure you only need to 'goto restart' if you call into
:maybe_resched() as someone else may have manipulated the queues.
:
:The 'restart' label is only in there for restarting in case one of
:the functions called may change the lists, if we restart _every_
:time we'll traverse the same procs where p->p_wchan != ident over
:and over needlessly.
:
:-Alfred

    Look at the code carefully.  It's *removing* the element from the list,
    the conditionally restarting rather then removing the element from the
    list and unconditionally restarting.  The only reason it works at all
    is because sys/queue.h does not clear out the pointers in the node 
    that was just removed.  The code is just plain wrong, though, because
    the queue mechanisms make no such (documented) guarentee.

					-Matt
					Matthew Dillon 
					<dillon@backplane.com>

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