Date: Tue, 15 May 2012 01:23:58 +0400 From: Andrey Zonov <andrey@zonov.org> To: Mateusz Guzik <mjguzik@gmail.com> Cc: trasz@freebsd.org, freebsd-stable <freebsd-stable@freebsd.org> Subject: Re: panic with overcommit and RACCT Message-ID: <4FB177EE.7030808@zonov.org> In-Reply-To: <20120513202920.GA18238@dft-labs.eu> References: <4FAFEEEF.3040706@zonov.org> <20120513202920.GA18238@dft-labs.eu>
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On 5/14/12 12:29 AM, Mateusz Guzik wrote: > On Sun, May 13, 2012 at 09:27:11PM +0400, Andrey Zonov wrote: >> Hi, >> >> I've got a repeatable panic on latest 9.0-STABLE and HEAD with >> turned on overcommit (vm.overcommit=1) and RACCT. >> >> kgdb trace on today's HEAD: >> >> #10 0xffffffff80bc3513 in calltrap () >> at /usr/src/sys/amd64/amd64/exception.S:228 >> #11 0xffffffff808aab71 in racct_set_locked (p=0xfffffe0005d684a0, >> resource=0, >> amount=2680) at /usr/src/sys/kern/kern_racct.c:372 >> #12 0xffffffff808ab645 in racct_proc_exit (p=0xfffffe0005d684a0) >> at /usr/src/sys/kern/kern_racct.c:615 >> #13 0xffffffff80880d69 in fork1 (td=0xfffffe0005b2c460, flags=20, pages=4, >> procp=0xffffff811a36bb00, procdescp=Variable "procdescp" is not >> available. >> ) at /usr/src/sys/kern/kern_fork.c:943 >> #14 0xffffffff80882362 in sys_fork (td=0xfffffe0005b2c460, >> uap=Variable "uap" is not available. >> ) >> at /usr/src/sys/kern/kern_fork.c:110 >> #15 0xffffffff80bd7a89 in amd64_syscall (td=0xfffffe0005b2c460, traced=0) >> at subr_syscall.c:135 >> #16 0xffffffff80bc37f7 in Xfast_syscall () >> at /usr/src/sys/amd64/amd64/exception.S:387 >> #17 0x00000008024729fc in ?? () >> Previous frame inner to this frame (corrupt stack?) >> (kgdb) >> >> Unread portion of the kernel message buffer: >> Kernel page fault with the following non-sleepable locks held: >> exclusive sleep mutex racct lock (racct lock) r = 0 >> (0xffffffff8128a7c0) locked @ /usr/src/sys/kern/kern_racct.c:614 >> exclusive sleep mutex process lock (process lock) r = 0 >> (0xfffffe0005d68598) locked @ /usr/src/sys/kern/kern_racct.c:603 >> > > It looks like racct_proc_exit can be called for processes without > properly initialized racct structure, which in turn results in this > panic. > > Can you please test this patch: > http://student.agh.edu.pl/~mjguzik/patches/racct-fork.patch > > ? > > I was unable to reproduce panic you describe, so it was tested only by > manually injecting error. Nevertheless I think you should try it. :) > Thanks, your patch fixes the panic. How to repeat: 1. add options RACCT and options RCTL to kernel config, rebuild and install kernel, reboot 2. set sysctl vm.overcommit=1 3. run as none root something that eats memory (I just run malloc() until it returns NULL) 4. swapoff -a 5. panic after sometime With patch applied instead of panic I got: "fork: Cannot allocate memory". Looks like a bug in overcommit code. -- Andrey Zonov
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