On 28.12.2012 03:45, Zhouping Liu wrote:

quoted

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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