Below is the output of running crash (with the patch) against one of these dumps. -Lucas crash 5.0.5 Copyright (C) 2002-2010 Red Hat, Inc. Copyright (C) 2004, 2005, 2006 IBM Corporation Copyright (C) 1999-2006 Hewlett-Packard Co Copyright (C) 2005, 2006 Fujitsu Limited Copyright (C) 2006, 2007 VA Linux Systems Japan K.K. Copyright (C) 2005 NEC Corporation Copyright (C) 1999, 2002, 2007 Silicon Graphics, Inc. Copyright (C) 1999, 2000, 2001, 2002 Mission Critical Linux, Inc. This program is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Enter "help copying" to see the conditions. This program has absolutely no warranty. Enter "help warranty" for details. GNU gdb (GDB) 7.0 Copyright (C) 2009 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Type "show copying" and "show warranty" for details. This GDB was configured as "x86_64-unknown-linux-gnu"... please wait... (determining panic task) WARNING: Loop detected in the NMI Exception Stack! bt: cannot transition from exception stack to current process stack: exception stack pointer: ffffffff8046dc50 process stack pointer: ffffffff8046ddd8 current stack base: ffffffff80422000 SYSTEM MAP: /boot/System.map-2.6.16.53-0.8.PTF.434477.9.TDC.0-smp DEBUG KERNEL: /boot/vmlinux-2.6.16.53-0.8.PTF.434477.9.TDC.0-smp (2.6.16.53-0.8.PTF.434477.9.TDC.0-smp) DUMPFILE: /var/crash/lucas.save/vmcore [PARTIAL DUMP] CPUS: 4 DATE: Tue May 18 12:46:07 2010 UPTIME: 07:24:54 LOAD AVERAGE: 85.74, 82.85, 82.29 TASKS: 2449 NODENAME: POLO5_1-9 RELEASE: 2.6.16.53-0.8.PTF.434477.9.TDC.0-smp VERSION: #1 SMP Fri Aug 31 06:07:27 PDT 2007 MACHINE: x86_64 (2660 Mhz) MEMORY: 7.9 GB PANIC: "Kernel panic - not syncing: dumpsw: Dump switch pushed; reason: 0x20 args=0xffffffff8046df08" PID: 0 COMMAND: "swapper" TASK: ffffffff8038c340 (1 of 4) [THREAD_INFO: ffffffff80422000] CPU: 0 STATE: TASK_RUNNING (PANIC) crash> bt PID: 0 TASK: ffffffff8038c340 CPU: 0 COMMAND: "swapper" #0 [ffffffff8046dc50] machine_kexec at ffffffff8011a95b #1 [ffffffff8046dd20] crash_kexec at ffffffff80154351 #2 [ffffffff8046dde0] panic at ffffffff801327fa #3 [ffffffff8046ded0] dumpsw_notify at ffffffff8831c0c3 #4 [ffffffff8046dee0] notifier_call_chain at ffffffff8032481f #5 [ffffffff8046df00] default_do_nmi at ffffffff80322fab #6 [ffffffff8046df40] do_nmi at ffffffff80323365 #7 [ffffffff8046df50] nmi at ffffffff8032268f [exception RIP: smp_send_stop+84] RIP: ffffffff80116e44 RSP: ffffffff8046ddd8 RFLAGS: 00000246 RAX: 00000000000000ff RBX: ffffffff8831c1f8 RCX: 000041049c7256e8 RDX: 0000000000000005 RSI: 000000005238a938 RDI: 00000000002896a0 RBP: ffffffff8046df08 R8: 00000000000040fb R9: 000000005238a7e8 R10: 0000000000000002 R11: 0000ffff0000ffff R12: 000000000000000c R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018 --- <NMI exception stack> --- #8 [ffffffff8046ddd8] smp_send_stop at ffffffff80116e44 bt: WARNING: Loop detected in the NMI Exception Stack! bt: cannot transition from exception stack to current process stack: exception stack pointer: ffffffff8046dc50 process stack pointer: ffffffff8046ddd8 current stack base: ffffffff80422000 crash> -----Original Message----- From: crash-utility-bounces@xxxxxxxxxx [mailto:crash-utility-bounces@xxxxxxxxxx] On Behalf Of Dave Anderson Sent: Friday, June 25, 2010 12:32 PM To: Discussion list for crash utility usage,maintenance and development Subject: Re: infinite loop in crash due to double-NMI on x86_64 system ----- "Lucas Silacci" <Lucas.Silacci@xxxxxxxxxxxx> wrote: > Hi, > > I've run into an issue where crash will enter an infinite loop while > decoding exception stacks if those stacks get corrupted. > > We've seen this on four different systems where the hardware generated > multiple NMIs and the second and subsequent NMIs caused the NMI > exception stack to be overwritten. When this condition is hit, the > bottom rsp on the NMI exception stack (which would normally point you > back to the kernel thread stack or possibly a different exception stack) > points you back into the middle of the same NMI exception stack. This > causes crash to infinitely loop when it tries to decode that exception > stack. > > Now clearly the root cause of the issue is faulty hardware that > generated multiple NMIs. However a very small change in crash can detect > this issue and stop the infinite loop from happening thereby allowing > you to get to a point in crash where you can actually tell that it was > an NMI that caused the system to dump. > > The patch is attached to this email. For x86_64 it will detect the > condition of any exception stack that points back at itself. > > Please feel free to ask me any questions on this. Wow, that's pretty interesting -- I've certainly never seen that before. Can you show me what the backtrace looks like with your patch applied? Thanks, Dave -- Crash-utility mailing list Crash-utility@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/crash-utility -- Crash-utility mailing list Crash-utility@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/crash-utility
