Date: Sat, 14 Dec 2002 19:37:31 -0500 From: "Brian F. Feldman" <green@FreeBSD.org> To: John Baldwin <jhb@FreeBSD.org> Cc: Kris Kennaway <kris@obsecurity.org>, current@FreeBSD.org, alpha@FreeBSD.org Subject: Re: UMA panic under load Message-ID: <200212150037.gBF0bVSM014040@green.bikeshed.org> In-Reply-To: Your message of "Thu, 12 Dec 2002 11:34:00 EST." <XFMail.20021212113400.jhb@FreeBSD.org>
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John Baldwin <jhb@FreeBSD.org> wrote: > > On 12-Dec-2002 Kris Kennaway wrote: > > I got this on an alpha tonight. It was under heavy load at the time > > (18 simultaneous package builds had just been spawned on the machine). > > Any ideas? > > > > Slab at 0xfffffc00042d3fb8, freei 2 = 0. > > panic: Duplicate free of item 0xfffffc00042d22e0 from zone 0xfffffc0007d31800(VMSPACE) > > > > db_print_backtrace() at db_print_backtrace+0x18 > > panic() at panic+0x104 > > uma_dbg_free() at uma_dbg_free+0x170 > > uma_zfree_arg() at uma_zfree_arg+0x150 > > vmspace_free() at vmspace_free+0xe4 > > swapout_procs() at swapout_procs+0x428 > > vm_daemon() at vm_daemon+0x74 > > fork_exit() at fork_exit+0xe0 > > exception_return() at exception_return > > --- root of call graph --- > > panic > > Stopped at Debugger+0x34: zapnot v0,#0xf,v0 <v0=0x0> > > db> > > I have seen this on a couple of different arch's I think. A vmspace > shouldn't be free'd here, it's refcount should not be that low. > I wonder if something is free'ing the vmspace w/o dropping the refcount? The problem appears to be that swapout_procs() is swapping out a process that is in the process of exiting (in exit1()) and having already relinquished its vmspace, but has not set PRS_ZOMBIE yet (which would be preventing the swapout). It's clearly not correct for a process in exit1() to be swapped out, and the vmspace _needs_ to be decremented in the correct place or resources are NEVER freed when the race is lost. -- Brian Fundakowski Feldman \'[ FreeBSD ]''''''''''\ <> green@FreeBSD.org <> bfeldman@tislabs.com \ The Power to Serve! \ Opinions expressed are my own. \,,,,,,,,,,,,,,,,,,,,,,\ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-alpha" in the body of the message
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