From: Andrea Parri <andrea.parri@amarulasolutions.com>
To: torvalds@linux-foundation.org, mingo@kernel.org,
gregkh@linuxfoundation.org, tglx@linutronix.de, hpa@zytor.com,
peterz@infradead.org, will.deacon@arm.com,
linux-kernel@vger.kernel.org
Cc: linux-tip-commits@vger.kernel.org
Subject: Re: [tip:locking/core] Documentation/atomic_t.txt: Clarify pure non-rmw usage
Date: Thu, 6 Jun 2019 10:44:21 +0200 [thread overview]
Message-ID: <20190606084421.GA5523@andrea> (raw)
In-Reply-To: <tip-fff9b6c7d26943a8eb32b58364b7ec6b9369746a@git.kernel.org>
On Mon, Jun 03, 2019 at 06:46:54AM -0700, tip-bot for Peter Zijlstra wrote:
> Commit-ID: fff9b6c7d26943a8eb32b58364b7ec6b9369746a
> Gitweb: https://git.kernel.org/tip/fff9b6c7d26943a8eb32b58364b7ec6b9369746a
> Author: Peter Zijlstra <peterz@infradead.org>
> AuthorDate: Fri, 24 May 2019 13:52:31 +0200
> Committer: Ingo Molnar <mingo@kernel.org>
> CommitDate: Mon, 3 Jun 2019 12:32:57 +0200
>
> Documentation/atomic_t.txt: Clarify pure non-rmw usage
>
> Clarify that pure non-RMW usage of atomic_t is pointless, there is
> nothing 'magical' about atomic_set() / atomic_read().
>
> This is something that seems to confuse people, because I happen upon it
> semi-regularly.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Acked-by: Will Deacon <will.deacon@arm.com>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Link: https://lkml.kernel.org/r/20190524115231.GN2623@hirez.programming.kicks-ass.net
> Signed-off-by: Ingo Molnar <mingo@kernel.org>
I'd appreciate if you could Cc: me in future changes to this doc.
(as currently suggested by get_maintainer.pl).
This is particularly annoying when you spend time to review such
changes:
https://lkml.kernel.org/r/20190528111558.GA9106@andrea
Thanks,
Andrea
> ---
> Documentation/atomic_t.txt | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/atomic_t.txt b/Documentation/atomic_t.txt
> index dca3fb0554db..89eae7f6b360 100644
> --- a/Documentation/atomic_t.txt
> +++ b/Documentation/atomic_t.txt
> @@ -81,9 +81,11 @@ Non-RMW ops:
>
> The non-RMW ops are (typically) regular LOADs and STOREs and are canonically
> implemented using READ_ONCE(), WRITE_ONCE(), smp_load_acquire() and
> -smp_store_release() respectively.
> +smp_store_release() respectively. Therefore, if you find yourself only using
> +the Non-RMW operations of atomic_t, you do not in fact need atomic_t at all
> +and are doing it wrong.
>
> -The one detail to this is that atomic_set{}() should be observable to the RMW
> +A subtle detail of atomic_set{}() is that it should be observable to the RMW
> ops. That is:
>
> C atomic-set
next prev parent reply other threads:[~2019-06-06 8:44 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-22 13:22 [PATCH 00/18] locking/atomic: atomic64 type cleanup Mark Rutland
2019-05-22 13:22 ` [PATCH 01/18] locking/atomic: crypto: nx: prepare for atomic64_read() conversion Mark Rutland
2019-06-03 13:34 ` [tip:locking/core] locking/atomic, crypto/nx: Prepare " tip-bot for Mark Rutland
2019-05-22 13:22 ` [PATCH 02/18] locking/atomic: s390/pci: prepare " Mark Rutland
2019-06-03 13:34 ` [tip:locking/core] locking/atomic, s390/pci: Prepare " tip-bot for Mark Rutland
2019-05-22 13:22 ` [PATCH 03/18] locking/atomic: generic: use s64 for atomic64 Mark Rutland
2019-05-22 21:16 ` Arnd Bergmann
2019-06-03 13:35 ` [tip:locking/core] locking/atomic: Use " tip-bot for Mark Rutland
2019-05-22 13:22 ` [PATCH 04/18] locking/atomic: alpha: use " Mark Rutland
2019-06-03 13:36 ` [tip:locking/core] locking/atomic, alpha: Use " tip-bot for Mark Rutland
2019-05-22 13:22 ` [PATCH 05/18] locking/atomic: arc: use " Mark Rutland
2019-05-23 23:10 ` Vineet Gupta
2019-06-03 13:36 ` [tip:locking/core] locking/atomic, arc: Use " tip-bot for Mark Rutland
2019-05-22 13:22 ` [PATCH 06/18] locking/atomic: arm: use " Mark Rutland
2019-06-03 13:37 ` [tip:locking/core] locking/atomic, arm: Use " tip-bot for Mark Rutland
2019-05-22 13:22 ` [PATCH 07/18] locking/atomic: arm64: use " Mark Rutland
2019-06-03 13:38 ` [tip:locking/core] locking/atomic, arm64: Use " tip-bot for Mark Rutland
2019-05-22 13:22 ` [PATCH 08/18] locking/atomic: ia64: use " Mark Rutland
2019-06-03 13:39 ` [tip:locking/core] locking/atomic, ia64: Use " tip-bot for Mark Rutland
2019-05-22 13:22 ` [PATCH 09/18] locking/atomic: mips: use " Mark Rutland
2019-06-03 13:39 ` [tip:locking/core] locking/atomic, mips: Use " tip-bot for Mark Rutland
2019-05-22 13:22 ` [PATCH 10/18] locking/atomic: powerpc: use " Mark Rutland
2019-05-23 13:27 ` Michael Ellerman
2019-06-03 13:40 ` [tip:locking/core] locking/atomic, powerpc: Use " tip-bot for Mark Rutland
2019-05-22 13:22 ` [PATCH 11/18] locking/atomic: riscv: fix atomic64_sub_if_positive() offset argument Mark Rutland
2019-05-22 19:06 ` Palmer Dabbelt
2019-06-03 13:41 ` [tip:locking/core] locking/atomic, riscv: Fix " tip-bot for Mark Rutland
2019-05-22 13:22 ` [PATCH 12/18] locking/atomic: riscv: use s64 for atomic64 Mark Rutland
2019-05-22 19:06 ` Palmer Dabbelt
2019-05-23 10:23 ` Mark Rutland
2019-06-03 13:41 ` [tip:locking/core] locking/atomic, riscv: Use " tip-bot for Mark Rutland
2019-05-22 13:22 ` [PATCH 13/18] locking/atomic: s390: use " Mark Rutland
2019-06-03 13:42 ` [tip:locking/core] locking/atomic, s390: Use " tip-bot for Mark Rutland
2019-05-22 13:22 ` [PATCH 14/18] locking/atomic: sparc: use " Mark Rutland
2019-06-03 13:43 ` [tip:locking/core] locking/atomic, sparc: Use " tip-bot for Mark Rutland
2019-05-22 13:22 ` [PATCH 15/18] locking/atomic: x86: use " Mark Rutland
2019-06-03 13:44 ` [tip:locking/core] locking/atomic, x86: Use " tip-bot for Mark Rutland
2019-05-22 13:22 ` [PATCH 16/18] locking/atomic: use s64 for atomic64_t on 64-bit Mark Rutland
2019-06-03 13:44 ` [tip:locking/core] locking/atomic: Use " tip-bot for Mark Rutland
2019-05-22 13:22 ` [PATCH 17/18] locking/atomic: crypto: nx: remove redundant casts Mark Rutland
2019-06-03 13:45 ` [tip:locking/core] locking/atomic, crypto/nx: Remove " tip-bot for Mark Rutland
2019-05-22 13:22 ` [PATCH 18/18] locking/atomic: s390/pci: remove " Mark Rutland
2019-06-03 13:46 ` [tip:locking/core] locking/atomic, s390/pci: Remove " tip-bot for Mark Rutland
2019-05-22 21:18 ` [PATCH 00/18] locking/atomic: atomic64 type cleanup Arnd Bergmann
2019-05-23 10:28 ` Mark Rutland
2019-05-23 8:30 ` Andrea Parri
2019-05-23 10:19 ` Mark Rutland
2019-05-23 11:20 ` Andrea Parri
2019-05-24 10:37 ` Peter Zijlstra
2019-05-24 11:18 ` Peter Zijlstra
2019-05-24 11:38 ` Greg KH
2019-05-24 11:42 ` Will Deacon
2019-05-24 11:52 ` Peter Zijlstra
2019-05-24 22:43 ` Andrea Parri
2019-05-28 10:47 ` Peter Zijlstra
2019-05-28 11:15 ` Andrea Parri
2019-06-03 13:46 ` [tip:locking/core] Documentation/atomic_t.txt: Clarify pure non-rmw usage tip-bot for Peter Zijlstra
2019-06-06 8:44 ` Andrea Parri [this message]
2019-06-06 9:04 ` Peter Zijlstra
2019-06-06 9:11 ` Andrea Parri
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