From: Vlastimil Babka <vbabka@suse.cz>
To: Thomas Gleixner <tglx@linutronix.de>,
Waiman Long <longman@redhat.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@kernel.org>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Roman Gushchin <guro@fb.com>
Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
linux-mm@kvack.org, Shakeel Butt <shakeelb@google.com>,
Muchun Song <songmuchun@bytedance.com>,
Luis Goncalves <lgoncalv@redhat.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH] mm/memcg: Disable task obj_stock for PREEMPT_RT
Date: Wed, 4 Aug 2021 09:39:23 +0200 [thread overview]
Message-ID: <93dfe0d4-c687-93f8-da75-c5d3c9bd0ac7@suse.cz> (raw)
In-Reply-To: <87h7g62jxm.ffs@tglx>
On 8/4/21 1:21 AM, Thomas Gleixner wrote:
> /*
> * The only protection from memory hotplug vs. drain_stock races is
> * that we always operate on local CPU stock here with IRQ disabled
> */
> - local_irq_save(flags);
> + local_lock_irqsave(memcg_stock_lock, flags);
> ...
> if (use_task_obj_stock())
> drain_obj_stock(&stock->task_obj);
>
> which is incomprehensible garbage.
>
> The comment above the existing local_irq_save() is garbage w/o any local
> lock conversion already today (and even before the commit which
> introduced stock::task_obj) simply because that comment does not explain
> the why.
Michal, this seems to be your comment from commit 72f0184c8a00 ("mm, memcg:
remove hotplug locking from try_charge"). Was "memory hotplug" a mistake,
because the rest of the commit is about cpu hotplug, and I don't really see a
memory hotplug connection there?
WARNING: multiple messages have this Message-ID (diff)
From: Vlastimil Babka <vbabka-AlSwsSmVLrQ@public.gmane.org>
To: Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>,
Waiman Long <longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>,
Michal Hocko <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
Vladimir Davydov
<vdavydov.dev-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
Andrew Morton
<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
Roman Gushchin <guro-b10kYP2dOMg@public.gmane.org>
Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
Shakeel Butt <shakeelb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
Muchun Song <songmuchun-EC8Uxl6Npydl57MIdRCFDg@public.gmane.org>,
Luis Goncalves <lgoncalv-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Sebastian Andrzej Siewior
<bigeasy-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>,
Daniel Bristot de Oliveira
<bristot-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Linus Torvalds
<torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
Subject: Re: [PATCH] mm/memcg: Disable task obj_stock for PREEMPT_RT
Date: Wed, 4 Aug 2021 09:39:23 +0200 [thread overview]
Message-ID: <93dfe0d4-c687-93f8-da75-c5d3c9bd0ac7@suse.cz> (raw)
In-Reply-To: <87h7g62jxm.ffs@tglx>
On 8/4/21 1:21 AM, Thomas Gleixner wrote:
> /*
> * The only protection from memory hotplug vs. drain_stock races is
> * that we always operate on local CPU stock here with IRQ disabled
> */
> - local_irq_save(flags);
> + local_lock_irqsave(memcg_stock_lock, flags);
> ...
> if (use_task_obj_stock())
> drain_obj_stock(&stock->task_obj);
>
> which is incomprehensible garbage.
>
> The comment above the existing local_irq_save() is garbage w/o any local
> lock conversion already today (and even before the commit which
> introduced stock::task_obj) simply because that comment does not explain
> the why.
Michal, this seems to be your comment from commit 72f0184c8a00 ("mm, memcg:
remove hotplug locking from try_charge"). Was "memory hotplug" a mistake,
because the rest of the commit is about cpu hotplug, and I don't really see a
memory hotplug connection there?
next prev parent reply other threads:[~2021-08-04 7:39 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-03 17:55 [PATCH] mm/memcg: Disable task obj_stock for PREEMPT_RT Waiman Long
2021-08-03 17:55 ` Waiman Long
2021-08-03 23:21 ` Thomas Gleixner
2021-08-03 23:21 ` Thomas Gleixner
2021-08-03 23:21 ` Thomas Gleixner
2021-08-04 1:40 ` Waiman Long
2021-08-04 1:40 ` Waiman Long
2021-08-04 8:52 ` Michal Hocko
2021-08-04 8:52 ` Michal Hocko
2021-08-04 16:00 ` Waiman Long
2021-08-04 16:00 ` Waiman Long
2021-08-04 7:39 ` Vlastimil Babka [this message]
2021-08-04 7:39 ` Vlastimil Babka
2021-08-04 8:33 ` Michal Hocko
2021-08-09 9:07 ` Michal Hocko
2021-08-09 9:07 ` Michal Hocko
2021-08-09 9:28 ` Vlastimil Babka
2021-08-09 9:28 ` Vlastimil Babka
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