Messages in this thread |  | | Date | Tue, 12 Nov 2013 21:01:56 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH v4] mm, oom: Fix race when selecting process to kill |
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On 11/11, Sameer Nanda wrote: > > The selection of the process to be killed happens in two spots: > first in select_bad_process and then a further refinement by > looking for child processes in oom_kill_process. Since this is > a two step process, it is possible that the process selected by > select_bad_process may get a SIGKILL just before oom_kill_process > executes. If this were to happen, __unhash_process deletes this > process from the thread_group list. This results in oom_kill_process > getting stuck in an infinite loop when traversing the thread_group > list of the selected process. > > Fix this race by adding a pid_alive check for the selected process > with tasklist_lock held in oom_kill_process.
OK, looks correct to me. Thanks.
Yes, this is a step backwards, hopefully we will revert this patch soon. I am starting to think something like while_each_thread_lame_but_safe() makes sense before we really fix this nasty (and afaics not simple) problem with with while_each_thread() (which should die).
Oleg.
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