From: David Laight <David.Laight@ACULAB.COM>
To: 'Hector Martin' <marcan@marcan.st>, Will Deacon <will@kernel.org>,
"Peter Zijlstra" <peterz@infradead.org>,
Arnd Bergmann <arnd@arndb.de>, Ingo Molnar <mingo@kernel.org>
Cc: Alan Stern <stern@rowland.harvard.edu>,
Andrea Parri <parri.andrea@gmail.com>,
Boqun Feng <boqun.feng@gmail.com>,
Nicholas Piggin <npiggin@gmail.com>,
David Howells <dhowells@redhat.com>,
Jade Alglave <j.alglave@ucl.ac.uk>,
Luc Maranget <luc.maranget@inria.fr>,
"Paul E. McKenney" <paulmck@kernel.org>,
Akira Yokosawa <akiyks@gmail.com>,
"Daniel Lustig" <dlustig@nvidia.com>,
Joel Fernandes <joel@joelfernandes.org>,
"Mark Rutland" <mark.rutland@arm.com>,
Jonathan Corbet <corbet@lwn.net>, Tejun Heo <tj@kernel.org>,
"jirislaby@kernel.org" <jirislaby@kernel.org>,
Marc Zyngier <maz@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Oliver Neukum <oneukum@suse.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
Asahi Linux <asahi@lists.linux.dev>,
"stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: RE: [PATCH] locking/atomic: Make test_and_*_bit() ordered on failure
Date: Wed, 17 Aug 2022 08:20:08 +0000 [thread overview]
Message-ID: <1135281ad4e84cc5ac0147772aa83787@AcuMS.aculab.com> (raw)
In-Reply-To: <20220816070311.89186-1-marcan@marcan.st>
...
> p += BIT_WORD(nr);
> - if (READ_ONCE(*p) & mask)
> - return 1;
> -
> old = arch_atomic_long_fetch_or(mask, (atomic_long_t *)p);
> return !!(old & mask);
> }
This looks like the same pattern (attempting to avoid a
locked bus cycle) that caused the qdisc code to sit on
transmit packets (even on x86).
That had some barriers in it (possibly nops on x86) that
didn't help - although the comments suggested otherwise.
I wonder if the pattern has been used anywhere else?
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
prev parent reply other threads:[~2022-08-17 8:20 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-16 7:03 [PATCH] locking/atomic: Make test_and_*_bit() ordered on failure Hector Martin
2022-08-16 8:16 ` Arnd Bergmann
2022-08-16 12:29 ` Jon Nettleton
2022-08-16 13:00 ` Will Deacon
2022-08-16 13:05 ` Jon Nettleton
2022-08-16 13:23 ` Marc Zyngier
2022-08-16 14:06 ` Will Deacon
2022-08-16 18:14 ` Matthew Wilcox
2022-08-16 14:04 ` Will Deacon
2022-08-16 14:30 ` Hector Martin
2022-08-16 17:36 ` Will Deacon
2022-08-16 17:49 ` Jon Nettleton
2022-08-16 18:02 ` Linus Torvalds
2022-08-17 5:40 ` Jon Nettleton
2022-08-17 8:20 ` David Laight [this message]
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