Michal Hocko wrote:

On Wed 01-06-16 00:53:03, Oleg Nesterov wrote:

quoted

On 05/31, Michal Hocko wrote:

quoted

Oleg has pointed out that can simplify both oom_adj_write and
oom_score_adj_write even further and drop the sighand lock. The only
purpose of the lock was to protect p->signal from going away but this
will not happen since ea6d290ca34c ("signals: make task_struct->signal
immutable/refcountable").

Sorry for confusion, I meant oom_adj_read() and oom_score_adj_read().

As for oom_adj_write/oom_score_adj_write we can remove it too, but then
we need to ensure (say, using cmpxchg) that unpriviliged user can not
not decrease signal->oom_score_adj_min if its oom_score_adj_write()
races with someone else (say, admin) which tries to increase the same
oom_score_adj_min.

I am introducing oom_adj_mutex in a later patch so I will move it here.

Can't we reuse oom_lock like

	if (mutex_lock_killable(&oom_lock))
		return -EINTR;

? I think that updating oom_score_adj unlikely races with OOM killer
invocation, and updating oom_score_adj should be a killable operation.

quoted

If you think this is not a problem - I am fine with this change. But
please also update oom_adj_read/oom_score_adj_read ;)

will do. It stayed in the blind spot... Thanks for pointing that out

Thanks!
-- 
Michal Hocko
SUSE Labs

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