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Biederman" Cc: Michal Hocko , Suren Baghdasaryan , christian.brauner@ubuntu.com, mingo@kernel.org, peterz@infradead.org, tglx@linutronix.de, esyr@redhat.com, christian@kellner.me, areber@redhat.com, shakeelb@google.com, cyphar@cyphar.com, adobriyan@gmail.com, akpm@linux-foundation.org, gladkov.alexey@gmail.com, walken@google.com, daniel.m.jordan@oracle.com, avagin@gmail.com, bernd.edlinger@hotmail.de, john.johansen@canonical.com, laoar.shao@gmail.com, timmurray@google.com, minchan@kernel.org, kernel-team@android.com, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 1/1] mm, oom_adj: don't loop through tasks in __set_oom_adj when not necessary Message-ID: <20200820140451.GC4546@redhat.com> References: <20200820002053.1424000-1-surenb@google.com> <87zh6pxzq6.fsf@x220.int.ebiederm.org> <20200820124241.GJ5033@dhcp22.suse.cz> <87lfi9xz7y.fsf@x220.int.ebiederm.org> <87d03lxysr.fsf@x220.int.ebiederm.org> <20200820132631.GK5033@dhcp22.suse.cz> <874koxxwn5.fsf@x220.int.ebiederm.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <874koxxwn5.fsf@x220.int.ebiederm.org> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Rspamd-Queue-Id: 55C891804A31D X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam01 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 08/20, Eric W. Biederman wrote: > > --- a/fs/exec.c > +++ b/fs/exec.c > @@ -1139,6 +1139,10 @@ static int exec_mmap(struct mm_struct *mm) > vmacache_flush(tsk); > task_unlock(tsk); > if (old_mm) { > + mm->oom_score_adj = old_mm->oom_score_adj; > + mm->oom_score_adj_min = old_mm->oom_score_adj_min; > + if (tsk->vfork_done) > + mm->oom_score_adj = tsk->vfork_oom_score_adj; too late, ->vfork_done is NULL after mm_release(). And this can race with __set_oom_adj(). Yes, the current code is racy too, but this change adds another race, __set_oom_adj() could already observe ->mm != NULL and update mm->oom_score_adj. Oleg.