From: David Laight <david.laight.linux@gmail•com>
To: Petr Mladek <pmladek@suse•com>
Cc: chensong_2000@189•cn, rafael@kernel•org, lenb@kernel•org,
mturquette@baylibre•com, sboyd@kernel•org,
viresh.kumar@linaro•org, agk@redhat•com, snitzer@kernel•org,
mpatocka@redhat•com, bmarzins@redhat•com, song@kernel•org,
yukuai@fnnas•com, linan122@huawei•com,
jason.wessel@windriver•com, danielt@kernel•org,
dianders@chromium•org, horms@kernel•org, davem@davemloft•net,
edumazet@google•com, kuba@kernel•org, pabeni@redhat•com,
paulmck@kernel•org, frederic@kernel•org, mcgrof@kernel•org,
petr.pavlu@suse•com, da.gomez@kernel•org,
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Subject: Re: [RFC PATCH 1/2] kernel/notifier: replace single-linked list with double-linked list for reverse traversal
Date: Thu, 16 Apr 2026 20:15:39 +0100 [thread overview]
Message-ID: <20260416201539.2cee3b99@pumpkin> (raw)
In-Reply-To: <aeD4H8P1DiPQoM8V@pathway.suse.cz>
On Thu, 16 Apr 2026 16:54:23 +0200
Petr Mladek <pmladek@suse•com> wrote:
> On Thu 2026-04-16 13:30:04, David Laight wrote:
> > On Wed, 15 Apr 2026 15:01:37 +0800
> > chensong_2000@189•cn wrote:
> >
> > > From: Song Chen <chensong_2000@189•cn>
> > >
> > > The current notifier chain implementation uses a single-linked list
> > > (struct notifier_block *next), which only supports forward traversal
> > > in priority order. This makes it difficult to handle cleanup/teardown
> > > scenarios that require notifiers to be called in reverse priority order.
> >
> > If it is only cleanup/teardown then the list can be order-reversed
> > as part of that process at the same time as the list is deleted.
>
> Interesting idea. But it won't work in all situations.
It is useful for things like locklessy queuing a request to be processed later.
Items can be added with a cmpxchg and the list grabbed by xchg of NULL.
The only downside is that reversing a list isn't cache friendly.
Thinks... although that may not be any worse than accessing the current 'tail'
to add to the end of a doubly linked (or singly linked with a tail ptr) list.
David
>
> Note that the motivation for this update are the module loader
> notifiers which are called several times for each loaded/removed module.
>
> Best Regards,
> Petr
>
next prev parent reply other threads:[~2026-04-16 19:15 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-15 7:01 [RFC PATCH 1/2] kernel/notifier: replace single-linked list with double-linked list for reverse traversal chensong_2000
2026-04-15 7:40 ` Christoph Hellwig
2026-04-16 10:33 ` Petr Mladek
2026-04-19 0:07 ` Song Chen
2026-04-16 12:30 ` David Laight
2026-04-16 14:54 ` Petr Mladek
2026-04-16 19:15 ` David Laight [this message]
2026-04-19 0:21 ` Song Chen
2026-04-20 5:44 ` Masami Hiramatsu
2026-04-21 9:05 ` Petr Mladek
2026-04-26 13:56 ` Song Chen
2026-04-26 14:14 ` Song Chen
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