Date: Tue, 24 May 2005 16:01:31 -0700 From: John-Mark Gurney <gurney_j@resnet.uoregon.edu> To: Ed Maste <emaste@phaedrus.sandvine.ca> Cc: freebsd-stable@freebsd.org Subject: Re: libc_r kqueue fd leak Message-ID: <20050524230131.GN959@funkthat.com> In-Reply-To: <20050524215153.GA35718@sandvine.com> References: <20050524165907.GA20674@sandvine.com> <20050524173648.GA29183@sandvine.com> <20050524215153.GA35718@sandvine.com>
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Ed Maste wrote this message on Tue, May 24, 2005 at 17:51 -0400:
> On Tue, May 24, 2005 at 01:36:48PM -0400, Ed Maste wrote:
>
> > On Tue, May 24, 2005 at 12:59:07PM -0400, Ed Maste wrote:
> >
> > > We discovered a kqueue leak when running one of our 4.x applications on
> > > FreeBSD 5.3 using the compat libc_r. It turns out it's caused by libc_r's
> > > close() failing.
> >
> > I've attached a patch which stops libc_r close() from bailing if fstat()
> > returns an error. This fixes the kqueue leak. This logic would also have
> > to make its way into the compat library via 4.x to fully resolve the issue.
>
> After a little more research it seems the kernel fix is already documented
> in threads/75795. Version 1.77 of kern_event.c changed kqueue_stat to just
> return ENXIO.
>
> We discovered the problem because each call in our app to getipnodebyname
> (and in turn the resolver) leaked one kqueue, which eventually used up all
> kernel memory and then caused a panic.
>
> I noticed that jmg originally did the kqueue locking work which removed
> kqueue_stat, hence the CC:.
yes, the reason I made _stat return ENXIO is that _read and _write are
not supported by kqueue, and so _stat provided useless information.
When I added locking, it would only be reading a value that would
immediately be able to be changed, making it informational at best..
You'd better spend your syscall calling kevent and getting a few
events off the queue than trying to figure out how much work you
have to do... (In one of my programs, I have code that dynamicly
increases the number of kevent structs I pull off if I get the max..)
After being pestered by ps, I have created a patch.. after a quick test
that it compiles and runs, I'll commit it... Though libc_r depending
upon _stat seems broken to me... Who knows what else doesn't implement
_stat and can't be closed..
--
John-Mark Gurney Voice: +1 415 225 5579
"All that I will do, has been done, All that I have, has not."
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