From: Peter Zijlstra <peterz@infradead.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Eric Dumazet <edumazet@google.com>,
Waiman Long <longman@redhat.com>,
Shakeel Butt <shakeelb@google.com>,
Eric Dumazet <eric.dumazet@gmail.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@redhat.com>, Boqun Feng <boqun.feng@gmail.com>,
Will Deacon <will@kernel.org>, Roman Penyaev <rpenyaev@suse.de>
Subject: Re: [PATCH] locking/rwlocks: do not starve writers
Date: Mon, 20 Jun 2022 09:25:06 +0200 [thread overview]
Message-ID: <YrAg0p+snFXCkGz1@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <CAHk-=wiEZmzBUFkZkBrJv3JSJkQ+qxaMZU_Sx1WTpMHs2SOAiQ@mail.gmail.com>
On Fri, Jun 17, 2022 at 02:48:08PM -0500, Linus Torvalds wrote:
> I'd love to see the tasklist_lock be converted to RCU too. But that
> locks predates RCU (and probably 99% of all kernel code), and it's
> messy, so nobody sane has ever willingly tried to do that afaik.
Thomas actually tried a few years ago (for RT, which also hates on RW
type locks). At the time he converted most users to RCU (since the
tasklist itself is also RCU protected), but there's a bunch of users
(more than you'd like) that really need to be exclusive vs fork.
IIRC the most prominent problem is that RCU iteration can miss incoming
tasks and they'll miss getting updated. But like said, it's a few years
ago so I'm a bit hazy on the details.
next prev parent reply other threads:[~2022-06-20 7:25 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-17 9:10 [PATCH] locking/rwlocks: do not starve writers Eric Dumazet
2022-06-17 12:07 ` Peter Zijlstra
2022-06-17 14:43 ` Waiman Long
2022-06-17 14:57 ` Shakeel Butt
2022-06-17 15:00 ` Waiman Long
2022-06-17 15:24 ` Eric Dumazet
2022-06-17 15:56 ` Peter Zijlstra
2022-06-17 17:41 ` Waiman Long
2022-06-17 17:45 ` Eric Dumazet
2022-06-17 18:57 ` Waiman Long
2022-06-17 19:04 ` Peter Zijlstra
2022-06-17 19:10 ` Eric Dumazet
2022-06-17 19:19 ` Linus Torvalds
2022-06-17 19:25 ` Eric Dumazet
2022-06-17 19:34 ` Linus Torvalds
2022-06-17 19:39 ` Eric Dumazet
2022-06-17 19:48 ` Linus Torvalds
2022-06-20 7:25 ` Peter Zijlstra [this message]
2022-06-21 16:55 ` Eric W. Biederman
2022-06-17 21:58 ` David Laight
2022-06-17 19:34 ` Shakeel Butt
2022-06-17 19:08 ` Linus Torvalds
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