Re: Processes hang in an unkillable state

From: Linus Torvalds
Date: Tue Apr 12 2011 - 16:23:37 EST

On Tue, Apr 12, 2011 at 1:03 PM, Robert ÅwiÄcki <robert@xxxxxxxxxxx> wrote:
>> Ok, applied Linus' patch and got the following (kdb dump in the attachment):
>> It contains references to sys_mlock, but in another process/user that
>> oopsed (there are iknowthis and iknowthis2 processes running under
>> test and test2 users). I think I'll simply disable sys_madvise in the
>> fuzzer; and treat this oops as a separate issue.

This does seem to be something else.

It looks like some kind of live-lock situation between two processes
both doing madvise() and causing vmtruncate_range() calls.

Miklos wrote this patch for something bad in this area to serialize
concurrent unmap_mapping_range() calls in order to not restart forever
on vm_truncate_count. That got merged into 2.6.38, so it's there, but
I wonder if there is some case it misses.

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