4.19-stable review patch. If anyone has any objections, please let me know.
------------------ From: Michal Hocko <[email protected]> commit b2b469939e93458753cfbf8282ad52636495965e upstream. 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] Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Michal Hocko <[email protected]> Reported-by: Tetsuo Handa <[email protected]> Acked-by: Johannes Weiner <[email protected]> Cc: David Rientjes <[email protected]> Cc: Yong-Taek Lee <[email protected]> Cc: <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- fs/proc/base.c | 4 ---- 1 file changed, 4 deletions(-) --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -1084,10 +1084,6 @@ static int __set_oom_adj(struct file *fi task_lock(p); if (!p->vfork_done && process_shares_mm(p, mm)) { - pr_info("updating oom_score_adj for %d (%s) from %d to %d because it shares mm with %d (%s). Report if this is unexpected.\n", - task_pid_nr(p), p->comm, - p->signal->oom_score_adj, oom_adj, - task_pid_nr(task), task->comm); p->signal->oom_score_adj = oom_adj; if (!legacy && has_capability_noaudit(current, CAP_SYS_RESOURCE)) p->signal->oom_score_adj_min = (short)oom_adj;
