Messages in this thread | | | Date | Mon, 25 Apr 2011 10:38:33 -0700 | From | Ben Greear <> | Subject | Re: Debugging hung tasks? |
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On 04/22/2011 08:55 PM, Randy Dunlap wrote: > On Fri, 22 Apr 2011 16:09:29 -0700 Ben Greear wrote: > >> I am testing lots of NFS traffic against an over-loaded and slow file server. >> >> I enabled the hung-task detection logic, and it's hitting after 180 >> seconds. >> >> First: Is there any valid reason to have funky NFS cause a hung task? >> >> Second: Why doesn't the hung-task panic logic print the stack trace of >> the hung task? >> Is this an option that can be enabled? > > hung_task.c::check_hung_task() always calls sched_show_task() and > optionally does the panic: > > if (sysctl_hung_task_panic) > panic("hung_task: blocked tasks"); > > sched.c::sched_show_task() calls show_stack(), which should be doing what > you are asking for AFAICT. What kernel version are you using?
Here's one of the panics, for instance (captured on serial console).
There is a lockdep splat in 2.6.36.4 early on, (known bug, but not fixed since that kernel is EOL), so that is probably why there is no locking info printed. But, I was expecting a more useful stack trace since it appears to be our user-space application (btserver) that is hung.
Apr 22 15:57:38 localhost kernel: nfs: server 192.168.100.19 not responding, still trying Apr 22 15:57:38 localhost kernel: nfs: server 192.168.100.19 OK Kernel panic - not syncing: hung_task: blocked tasks Pid: 58, comm: khungtaskd Not tainted 2.6.36.4+ #1 Apr 22 15:59:08 Call Trace: localhost kernel [<ffffffff8140174a>] panic+0x96/0x1ae : INFO: task bts [<ffffffff81093106>] watchdog+0x1b1/0x1f9 erver:15212 bloc [<ffffffff81092f55>] ? watchdog+0x0/0x1f9 ked for more tha [<ffffffff8105c774>] kthread+0x7d/0x85 n 180 seconds. [<ffffffff8100a8e4>] kernel_thread_helper+0x4/0x10 Apr 22 15:59:08 [<ffffffff81404a54>] ? restore_args+0x0/0x30 localhost kernel [<ffffffff8105c6f7>] ? kthread+0x0/0x85 : "echo 0 > /pro [<ffffffff8100a8e0>] ? kernel_thread_helper+0x0/0x10 c/sys/kernel/hunpanic occurred, switching back to text console Rebooting in 10 seconds..^C
We're testing 2.6.38.4 now..haven't seen this problem again, so maybe it's fixed anyway...
Thanks, Ben
-- Ben Greear <greearb@candelatech.com> Candela Technologies Inc http://www.candelatech.com
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