On 2019/02/13 5:56, Andrew Morton wrote: > On Tue, 12 Feb 2019 11:21:29 +0100 Michal Hocko <[email protected]> wrote: > >> Tetsuo has reported that creating a thousands of processes sharing MM >> without SIGHAND (aka alien threads) and setting >> /proc/<pid>/oom_score_adj will swamp the kernel log and takes ages [1] >> to finish. This is especially worrisome that all that printing is done >> under RCU lock and this can potentially trigger RCU stall or softlockup >> detector. >> >> The primary reason for the printk was to catch potential users who might >> depend on the behavior prior to 44a70adec910 ("mm, oom_adj: make sure >> processes sharing mm have same view of oom_score_adj") but after more >> than 2 years without a single report I guess it is safe to simply remove >> the printk altogether. >> >> The next step should be moving oom_score_adj over to the mm struct and >> remove all the tasks crawling as suggested by [2] >> >> [1] >> http://lkml.kernel.org/r/[email protected] >> [2] http://lkml.kernel.org/r/[email protected] > > I think I'll put a cc:stable on this. Deleting a might-trigger debug > printk is safe and welcome. >
Putting cc:stable is fine. But I doubt the usefulness of this patch. If nobody really depends on the behavior prior to 44a70adec910, we should remove the pointless (otherwise racy) iteration itself.
