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charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 00C9A40014 X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: qecneyhshqczyepz76frsnpwbhrbmx58 X-HE-Tag: 1678287131-855351 X-HE-Meta: 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 +e91n1wu 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 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 Tue, Mar 7, 2023 at 1:53=E2=80=AFAM Michal Hocko wrote= : > > On Mon 06-03-23 23:41:37, Yue Zhao wrote: > > The knob for cgroup v1 memory controller: memory.oom_control > > is not protected by any locking so it can be modified while it is used. > > This is not an actual problem because races are unlikely. > > But it is better to use READ_ONCE/WRITE_ONCE to prevent compiler from > > doing anything funky. > > > > The access of memcg->oom_kill_disable is lockless, > > so it can be concurrently set at the same time as we are > > trying to read it. > > > > Signed-off-by: Yue Zhao > > --- > > mm/memcontrol.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > index dca895c66a9b..26605b2f51b1 100644 > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -4515,7 +4515,7 @@ static int mem_cgroup_oom_control_read(struct seq= _file *sf, void *v) > > { > > struct mem_cgroup *memcg =3D mem_cgroup_from_seq(sf); > > > > - seq_printf(sf, "oom_kill_disable %d\n", memcg->oom_kill_disable); > > + seq_printf(sf, "oom_kill_disable %d\n", READ_ONCE(memcg->oom_kill= _disable)); > > seq_printf(sf, "under_oom %d\n", (bool)memcg->under_oom); > > seq_printf(sf, "oom_kill %lu\n", > > atomic_long_read(&memcg->memory_events[MEMCG_OOM_KILL]= )); > > @@ -4531,7 +4531,7 @@ static int mem_cgroup_oom_control_write(struct cg= roup_subsys_state *css, > > if (mem_cgroup_is_root(memcg) || !((val =3D=3D 0) || (val =3D=3D = 1))) > > return -EINVAL; > > > > - memcg->oom_kill_disable =3D val; > > + WRITE_ONCE(memcg->oom_kill_disable, val); > > if (!val) > > memcg_oom_recover(memcg); > > Any specific reasons you haven't covered other accesses > (mem_cgroup_css_alloc, mem_cgroup_oom, mem_cgroup_oom_synchronize)? Thanks for point this out, you are right, we should add [READ|WRITE]_ONCE for all used places. Let me create PATCH v3 later. Also for the memcg->soft_limit, I will update as well. > > > > -- > > 2.17.1 > > -- > Michal Hocko > SUSE Labs