Messages in this thread | | | Date | Fri, 19 Aug 2016 15:00:26 +0100 | From | Mel Gorman <> | Subject | Re: [PATCH] mm: Add WARN_ON for possibility of infinite loop if empty lists in free_pcppages_bulk' |
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On Fri, Aug 19, 2016 at 09:07:21AM -0400, Pankaj Gupta wrote: > > > > > On Fri, Aug 19, 2016 at 05:45:18PM +0530, Pankaj Gupta wrote: > > > While debugging issue in realtime kernel i found a scenario > > > which resulted in infinite loop resulting because of empty pcp->lists > > > and valid 'to_free' value. This patch is to add 'WARN_ON' in function > > > 'free_pcppages_bulk' if there is possibility of infinite loop because > > > of any bug in code. > > > > > > > What was the bug that allowed this situation to occur? It would imply > > the pcp count was somehow out of sync. > > Yes pcp count was out of sync. It was a bug in the downstream code.
If the bug is not in the mainline code, I think it would be inappropriate to add unnecessary code to a relatively hot path. At most, it should be a VM_BUG_ON but the soft lockup should be clear enough.
-- Mel Gorman SUSE Labs
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