Messages in this thread | | | Date | Fri, 28 Dec 2012 13:57:31 +0100 | From | Zlatko Calusic <> | Subject | Re: BUG: unable to handle kernel NULL pointer dereference at 0000000000000500 |
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On 28.12.2012 03:45, Zhouping Liu wrote: >> >> Thank you for the report Zhouping! >> >> Would you be so kind to test the following patch and report results? >> Apply the patch to the latest mainline. > > Hello Zlatko, > > I have tested the below patch(applied it on mainline directly), > but IMO, I'd like to say it maybe don't fix the issue completely. > > run the reproducer[1] on two machine, one machine has 2 numa nodes(8Gb RAM), > another one has 4 numa nodes(8Gb RAM), then the system hung all the time, such as the dmesg log: > > [ 713.066937] Killed process 6085 (oom01) total-vm:18880768kB, anon-rss:7915612kB, file-rss:4kB > [ 959.555269] INFO: task kworker/13:2:147 blocked for more than 120 seconds. > [ 959.562144] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > [ 1079.382018] INFO: task kworker/13:2:147 blocked for more than 120 seconds. > [ 1079.388872] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > [ 1199.209709] INFO: task kworker/13:2:147 blocked for more than 120 seconds. > [ 1199.216562] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > [ 1319.036939] INFO: task kworker/13:2:147 blocked for more than 120 seconds. > [ 1319.043794] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > [ 1438.864797] INFO: task kworker/13:2:147 blocked for more than 120 seconds. > [ 1438.871649] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > [ 1558.691611] INFO: task kworker/13:2:147 blocked for more than 120 seconds. > [ 1558.698466] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > ...... > > I'm not sure whether it's your patch triggering the hung task or not, but reverted cda73a10eb3, > the reproducer(oom01) can PASS without both 'NULL pointer dereference at 0000000000000500' and hung task issues. > > but some time, it's possible that the reproducer(oom01) cause hung task on a box with large RAM(100Gb+), so I can't judge it... >
Thanks for the test.
Yes, close to OOM things get quite unstable and it's hard to get reliable test results. Maybe you could run it a few times, and see if you can get any meaningful statistics out of a few runs. I need to check oom.c myself and see what it's doing. Thanks for the link.
Regards, -- Zlatko
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