From: Mike Snitzer <snitzer@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Tejun Heo <tj@kernel.org>, Mikulas Patocka <mpatocka@redhat.com>,
linux-kernel@vger.kernel.org, dm-devel@lists.linux.dev,
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, Alasdair Kergon <agk@redhat.com>
Subject: Re: [PATCH 8/8] dm-verity: Convert from tasklet to BH workqueue
Date: Wed, 31 Jan 2024 19:07:57 -0500 [thread overview]
Message-ID: <Zbrg3aRFkgS7XCFE@redhat.com> (raw)
In-Reply-To: <CAHk-=wjMz_1mb+WJsPhfp5VBNrM=o8f-x2=6UW2eK5n4DHff9g@mail.gmail.com>
On Wed, Jan 31 2024 at 6:19P -0500,
Linus Torvalds <torvalds@linux-foundation.org> wrote:
> On Wed, 31 Jan 2024 at 13:32, Tejun Heo <tj@kernel.org> wrote:
> >
> > I don't know, so just did the dumb thing. If the caller always guarantees
> > that the work items are never queued at the same time, reusing is fine.
>
> So the reason I thought it would be a good cleanup to introduce that
> "atomic" workqueue thing (now "bh") was that this case literally has a
> switch between "use tasklets' or "use workqueues".
>
> So it's not even about "reusing" the workqueue, it's literally a
> matter of making it always just use workqueues, and the switch then
> becomes just *which* workqueue to use - system or bh.
DM generally always use dedicated workqueues instead of the system.
The dm-crypt tasklet's completion path did punt to the workqueue
otherwise there was use-after-free of the per-bio-data that included
the tasklet. And for verity there was fallback to workqueue if
tasklet-based verification failed. Didn't inspire confidence.
> In fact, I suspect there is very little reason ever to *not* just use
> the bh one, and even the switch could be removed.
>
> Because I think the only reason the "workqueue of tasklet" choice
> existed in the first place was that workqueues were the "proper" data
> structure, and the tasklet case was added later as a latency hack, and
> everybody knew that tasklets were deprecated.
Correct, abusing tasklets was a very contrived latency optimization.
Happy to see it all go away! (hindsight: it never should have gone in).
Mike
next prev parent reply other threads:[~2024-02-01 0:08 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
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 [this message]
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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