Date: Sun, 28 Mar 2010 23:52:23 +0100 (BST) From: Robert Watson <rwatson@FreeBSD.org> To: Jilles Tjoelker <jilles@stack.nl> Cc: svn-src-stable@freebsd.org, svn-src-all@freebsd.org, Doug Barton <dougb@FreeBSD.org>, src-committers@freebsd.org, svn-src-stable-8@freebsd.org Subject: Re: svn commit: r205806 - stable/8/etc Message-ID: <alpine.BSF.2.00.1003282351320.522@fledge.watson.org> In-Reply-To: <20100328210630.GA2086@stack.nl> References: <201003282019.o2SKJfPg033857@svn.freebsd.org> <4BAFBBFA.7020701@FreeBSD.org> <20100328210630.GA2086@stack.nl>
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On Sun, 28 Mar 2010, Jilles Tjoelker wrote: > On Sun, Mar 28, 2010 at 01:28:42PM -0700, Doug Barton wrote: >> Probably my fault for not saying something sooner, but there is a problem >> with the code in head that sometimes causes it to loop repeatedly even >> though pwait exits successfully. I am trying to track it down, but since it >> only happens about once every 10 shutdowns it's been difficult. > > There is a difference between the two methods in what is waited for exactly. > pwait(1) will wait for the process to terminate; if it is applied to a > zombie it will return immediately (printing the exit status if -v was > given). On the other hand, kill(1) will continue to return success until the > process has been waited for by its parent. > > An obvious fix is to trust pwait if it returns successfully, e.g. like if > pwait $_list 2>/dev/null; then break; else sleep 2; fi I noticed last year that Apple has implemented a separate PROC_REAP event in kqueue -- it would be easy for us to implement that as well, and add a flag to pwait to allow the user to decide to use that semantic instead (if desired). Robert N M Watson Computer Laboratory University of Cambridge
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