Messages in this thread | | | Date | Thu, 6 Apr 2017 14:06:14 +0100 | From | Mel Gorman <> | Subject | Re: Is it safe for kthreadd to drain_all_pages? |
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On Wed, Apr 05, 2017 at 01:59:49PM -0700, Hugh Dickins wrote: > Hi Mel, > > I suspect that it's not safe for kthreadd to drain_all_pages(); > but I haven't studied flush_work() etc, so don't really know what > I'm talking about: hoping that you will jump to a realization. >
You're right, it's not safe. If kthreadd is creating the workqueue thread to do the drain and it'll recurse into itself.
> 4.11-rc has been giving me hangs after hours of swapping load. At > first they looked like memory leaks ("fork: Cannot allocate memory"); > but for no good reason I happened to do "cat /proc/sys/vm/stat_refresh" > before looking at /proc/meminfo one time, and the stat_refresh stuck > in D state, waiting for completion of flush_work like many kworkers. > kthreadd waiting for completion of flush_work in drain_all_pages(). >
It's asking itself to do work in all likelihood.
> Patch below has been running well for 36 hours now: > a bit too early to be sure, but I think it's time to turn to you. >
I think the patch is valid but like Michal, would appreciate if you could run the patch he linked to see if it also side-steps the same problem.
Good spot!
-- Mel Gorman SUSE Labs
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