From: Boqun Feng <boqun.feng@gmail.com>
To: Tejun Heo <tj@kernel.org>
Cc: torvalds@linux-foundation.org, mpatocka@redhat.com,
linux-kernel@vger.kernel.org, dm-devel@lists.linux.dev,
msnitzer@redhat.com, ignat@cloudflare.com, damien.lemoal@wdc.com,
bob.liu@oracle.com, houtao1@huawei.com, peterz@infradead.org,
mingo@kernel.org, netdev@vger.kernel.org, allen.lkml@gmail.com,
kernel-team@meta.com, Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH for-6.9] workqueue: Drain BH work items on hot-unplugged CPUs
Date: Thu, 29 Feb 2024 13:07:21 -0800 [thread overview]
Message-ID: <ZeDyCSxtshb6MFLA@boqun-archlinux> (raw)
In-Reply-To: <ZeDrCMLlzVZpvbrG@slm.duckdns.org>
On Thu, Feb 29, 2024 at 10:37:28AM -1000, Tejun Heo wrote:
> On Mon, Feb 26, 2024 at 03:38:55PM -1000, Tejun Heo wrote:
> > Boqun pointed out that workqueues aren't handling BH work items on offlined
> > CPUs. Unlike tasklet which transfers out the pending tasks from
> > CPUHP_SOFTIRQ_DEAD, BH workqueue would just leave them pending which is
> > problematic. Note that this behavior is specific to BH workqueues as the
> > non-BH per-CPU workers just become unbound when the CPU goes offline.
> >
> > This patch fixes the issue by draining the pending BH work items from an
> > offlined CPU from CPUHP_SOFTIRQ_DEAD. Because work items carry more context,
> > it's not as easy to transfer the pending work items from one pool to
> > another. Instead, run BH work items which execute the offlined pools on an
> > online CPU.
> >
> > Note that this assumes that no further BH work items will be queued on the
> > offlined CPUs. This assumption is shared with tasklet and should be fine for
> > conversions. However, this issue also exists for per-CPU workqueues which
> > will just keep executing work items queued after CPU offline on unbound
> > workers and workqueue should reject per-CPU and BH work items queued on
> > offline CPUs. This will be addressed separately later.
> >
> > Signed-off-by: Tejun Heo <tj@kernel.org>
> > Reported-by: Boqun Feng <boqun.feng@gmail.com>
> > Link: http://lkml.kernel.org/r/Zdvw0HdSXcU3JZ4g@boqun-archlinux
>
> Applying this to wq/for-6.9.
>
FWIW,
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
(I took a look yesterday, but hasn't gotten the time to reply..)
Regards,
Boqun
> Thanks.
>
> --
> tejun
next prev parent reply other threads:[~2024-02-29 21:08 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-30 9:11 [PATCHSET wq/for-6.9] workqueue: Implement BH workqueue and convert several tasklet users Tejun Heo
2024-01-30 9:11 ` [PATCH 1/8] workqueue: Update lock debugging code Tejun Heo
2024-01-30 9:11 ` [PATCH 2/8] workqueue: Factor out init_cpu_worker_pool() Tejun Heo
2024-01-30 9:11 ` [PATCH 3/8] workqueue: Implement BH workqueues to eventually replace tasklets Tejun Heo
2024-01-30 17:25 ` Linus Torvalds
2024-02-01 11:02 ` Lai Jiangshan
2024-02-01 21:47 ` Tejun Heo
2024-02-02 1:15 ` [PATCH v2 " Tejun Heo
2024-02-04 2:20 ` Lai Jiangshan
2024-02-04 21:29 ` [PATCH v3 " Tejun Heo
2024-02-05 4:48 ` Hillf Danton
2024-02-05 17:47 ` Tejun Heo
2024-02-26 2:00 ` Boqun Feng
2024-02-26 18:47 ` Tejun Heo
2024-02-27 1:38 ` [PATCH for-6.9] workqueue: Drain BH work items on hot-unplugged CPUs Tejun Heo
2024-02-29 20:37 ` Tejun Heo
2024-02-29 21:07 ` Boqun Feng [this message]
2024-01-30 9:11 ` [PATCH 4/8] backtracetest: Convert from tasklet to BH workqueue Tejun Heo
2024-01-30 9:11 ` [PATCH 5/8] usb: core: hcd: " Tejun Heo
2024-01-30 16:38 ` Greg Kroah-Hartman
2024-02-20 17:25 ` Davidlohr Bueso
2024-02-20 17:55 ` Linus Torvalds
2024-02-20 18:19 ` Tejun Heo
2024-02-20 19:36 ` Davidlohr Bueso
2024-01-30 9:11 ` [PATCH 6/8] net: tcp: tsq: " Tejun Heo
2024-02-16 5:31 ` Tejun Heo
2024-02-16 8:23 ` Eric Dumazet
2024-02-16 15:52 ` David Wei
2024-02-16 16:24 ` Tejun Heo
2024-01-30 9:11 ` [PATCH 7/8] dm-crypt: " Tejun Heo
2024-01-30 10:46 ` Sebastian Andrzej Siewior
2024-01-30 15:53 ` Tejun Heo
2024-01-31 21:23 ` Mikulas Patocka
2024-01-30 9:11 ` [PATCH 8/8] dm-verity: " Tejun Heo
2024-01-31 21:19 ` Mikulas Patocka
2024-01-31 21:32 ` Tejun Heo
2024-01-31 22:02 ` Mikulas Patocka
2024-01-31 23:19 ` Linus Torvalds
2024-02-01 0:04 ` Tejun Heo
2024-02-01 0:19 ` Mike Snitzer
2024-02-20 19:44 ` Mike Snitzer
2024-02-20 20:05 ` Tejun Heo
2024-02-22 21:24 ` Mike Snitzer
2024-02-23 17:22 ` Tejun Heo
2024-02-01 0:07 ` Mike Snitzer
2024-01-30 9:22 ` [PATCHSET wq/for-6.9] workqueue: Implement BH workqueue and convert several tasklet users Tejun Heo
2024-01-30 10:20 ` Sebastian Andrzej Siewior
2024-01-30 15:50 ` Tejun Heo
2024-01-30 23:37 ` Allen
2024-02-04 21:33 ` Tejun Heo
2024-02-05 20:50 ` Allen
2024-02-05 21:12 ` Tejun Heo
2024-02-05 21:31 ` Allen
2024-02-07 19:02 ` Allen
2024-02-08 16:56 ` Tejun Heo
2024-02-08 19:07 ` Allen
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