Re: [PATCH 1/3] [PATCH i386] during VM oom condition, kill all threads in process group

From: Eric W. Biederman
Date: Fri Jun 08 2007 - 18:50:48 EST

Will Schmidt <will_schmidt@xxxxxxxxxxxx> writes:

> On Fri, 2007-06-08 at 12:32 -0700, Andrew Morton wrote:
>> On Fri, 08 Jun 2007 14:19:18 -0500
>> Will Schmidt <will_schmidt@xxxxxxxxxxxx> wrote:
>> > > > > zap_other_threads() requires tasklist_lock.
>> >
>> In fact, it's probably the case that rcu_read_lock() is now sufficient
>> locking coverage for zap_other_threads() (cc's people).
>> It had better be, because do_group_exit() forgot to take tasklist_lock. It
>> is perhaps relying upon spin_lock()'s hidden rcu_read_lock() properties
>> without so much as a code comment, which would be somewhat nasty of it.
>> You could perhaps just call do_group_exit() from within the fault
>> handler,
>> btw.
> Yup, so looks like I can actually replace the existing do_exit() call
> with do_group_exit(). I'll sit on this for a bit to give other folks a
> chance to comment on which lock call is sufficient, read_lock() or
> rcu_read_lock(), etc; and do_group_exit()'s issue with taking
> tasklist_lock.

No. The rcu_read_lock is not sufficient.
Yes. sighand->siglock is enough, and we explicitly take it in
do_group_exit before calling zap_other_threads.

Unless I have completely miss-understood this thread.

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