From: bsegall@google.com
To: Muchun Song <songmuchun@bytedance.com>
Cc: mingo@kernel.org, peterz@infradead.org, juri.lelli@redhat.com,
vincent.guittot@linaro.org, linux-kernel@vger.kernel.org,
dietmar.eggemann@arm.com, rostedt@goodmis.org,
bsegall@google.com, mgorman@suse.de
Subject: Re: [PATCH] sched/fair: Fix call walk_tg_tree_from() without hold rcu_lock
Date: Mon, 06 Apr 2020 11:17:19 -0700 [thread overview]
Message-ID: <xm26imico4wg.fsf@google.com> (raw)
In-Reply-To: <20200406121008.62903-1-songmuchun@bytedance.com> (Muchun Song's message of "Mon, 6 Apr 2020 20:10:08 +0800")
Muchun Song <songmuchun@bytedance.com> writes:
> The walk_tg_tree_from() caller must hold rcu_lock, but the caller
> do not call rcu_read_lock() in the unthrottle_cfs_rq(). The
> unthrottle_cfs_rq() is used in 3 places. There are
> distribute_cfs_runtime(), unthrottle_offline_cfs_rqs() and
> tg_set_cfs_bandwidth(). The former 2 already hold the rcu lock,
> but the last one does not. So fix it with calling rcu_read_lock()
> in the unthrottle_cfs_rq().
It might be a tiny bit better to put it in the tg_set_cfs_bandwidth
instead, but the other two sources were kinda by accident, so this is
reasonable too.
Reviewed-by: Ben Segall <bsegall@google.com>
>
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> ---
> kernel/sched/fair.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 6f05843c76d7d..870853c47b63c 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4782,7 +4782,9 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
> raw_spin_unlock(&cfs_b->lock);
>
> /* update hierarchical throttle state */
> + rcu_read_lock();
> walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
> + rcu_read_unlock();
>
> if (!cfs_rq->load.weight)
> return;
next prev parent reply other threads:[~2020-04-06 18:17 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-06 12:10 [PATCH] sched/fair: Fix call walk_tg_tree_from() without hold rcu_lock Muchun Song
2020-04-06 18:17 ` bsegall [this message]
2020-04-13 15:00 ` [External] " 宋牧春
2020-04-21 13:52 ` Peter Zijlstra
2020-04-21 15:43 ` Paul E. McKenney
2020-04-21 16:24 ` Peter Zijlstra
2020-04-21 17:39 ` Paul E. McKenney
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=xm26imico4wg.fsf@google.com \
--to=bsegall@google.com \
--cc=dietmar.eggemann@arm.com \
--cc=juri.lelli@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mgorman@suse.de \
--cc=mingo@kernel.org \
--cc=peterz@infradead.org \
--cc=rostedt@goodmis.org \
--cc=songmuchun@bytedance.com \
--cc=vincent.guittot@linaro.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).