From: Mark Rutland <mark.rutland@arm.com>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: rcu@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel-team@fb.com, rostedt@goodmis.org,
Neeraj Upadhyay <quic_neeraju@quicinc.com>,
Frederic Weisbecker <frederic@kernel.org>,
Boqun Feng <boqun.feng@gmail.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
John Ogness <john.ogness@linutronix.de>,
Petr Mladek <pmladek@suse.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH RFC v2 rcu 6/8] arch/arm64: Add ARCH_HAS_NMI_SAFE_THIS_CPU_OPS Kconfig option
Date: Wed, 5 Oct 2022 12:12:29 +0100 [thread overview]
Message-ID: <Yz1mneessxDSN8V7@FVFF77S0Q05N> (raw)
In-Reply-To: <20220929180731.2875722-6-paulmck@kernel.org>
Hi Paul,
On Thu, Sep 29, 2022 at 11:07:29AM -0700, Paul E. McKenney wrote:
> The arm64 architecture uses either an LL/SC loop (old systems) or an LSE
> stadd instruction (new systems) to implement this_cpu_add(), both of which
> are NMI safe.
IIUC "NMI safe" here just means atomic w.r.t. an NMI being taken and modfying
the same location the atomic was targetting (i.e. just like
ARCH_HAVE_NMI_SAFE_CMPXCHG, which arm64 selects today).
Assuming so:
Acked-by: Mark Rutland <mark.rutland@arm.com>
Only this patch went to LAKML, so maybe an earlier patch made that clear, but
I didn't spot it.
As one minor nit, it would be nice to align the naming with
ARCH_HAVE_NMI_SAFE_CMPXCHG and select them next to each other in the Kconfig
file is possible, but the Ack stands regardless.
Thanks,
Mark.
> This means that the old and more-efficient srcu_read_lock()
> may be used in NMI context, without the need for srcu_read_lock_nmisafe().
> Therefore, add the new Kconfig option ARCH_HAS_NMI_SAFE_THIS_CPU_OPS to
> arch/arm64/Kconfig, which will cause NEED_SRCU_NMI_SAFE to be deselected,
> thus preserving the current srcu_read_lock() behavior.
>
> Link: https://lore.kernel.org/all/20220910221947.171557773@linutronix.de/
>
> Suggested-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
> Suggested-by: Frederic Weisbecker <frederic@kernel.org>
> Suggested-by: Boqun Feng <boqun.feng@gmail.com>
> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: John Ogness <john.ogness@linutronix.de>
> Cc: Petr Mladek <pmladek@suse.com>
> Cc: <linux-arm-kernel@lists.infradead.org>
> ---
> arch/arm64/Kconfig | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 571cc234d0b3..664725a0b5dd 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -31,6 +31,7 @@ config ARM64
> select ARCH_HAS_KCOV
> select ARCH_HAS_KEEPINITRD
> select ARCH_HAS_MEMBARRIER_SYNC_CORE
> + select ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
> select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
> select ARCH_HAS_PTE_DEVMAP
> select ARCH_HAS_PTE_SPECIAL
> --
> 2.31.1.189.g2e36527f23
>
next prev parent reply other threads:[~2022-10-05 11:12 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-21 14:46 [PATCH rcu 0/4] NMI-safe SRCU reader API Paul E. McKenney
2022-09-21 14:46 ` [PATCH RFC rcu 1/4] srcu: Convert ->srcu_lock_count and ->srcu_unlock_count to atomic Paul E. McKenney
2022-09-21 14:46 ` [PATCH RFC rcu 2/4] srcu: Create and srcu_read_lock_nmisafe() and srcu_read_unlock_nmisafe() Paul E. McKenney
2022-09-21 14:46 ` [PATCH RFC rcu 3/4] srcu: Check for consistent per-CPU per-srcu_struct NMI safety Paul E. McKenney
2022-09-21 14:46 ` [PATCH RFC rcu 4/4] srcu: Check for consistent global " Paul E. McKenney
2022-09-29 18:07 ` [PATCH v2 rcu 0/8] NMI-safe SRCU reader API Paul E. McKenney
2022-09-29 18:07 ` [PATCH RFC v2 rcu 1/8] srcu: Convert ->srcu_lock_count and ->srcu_unlock_count to atomic Paul E. McKenney
2022-09-30 15:02 ` John Ogness
2022-09-30 15:35 ` Paul E. McKenney
2022-09-30 20:37 ` John Ogness
2022-10-01 16:51 ` Paul E. McKenney
2022-09-29 18:07 ` [PATCH RFC v2 rcu 2/8] srcu: Create an srcu_read_lock_nmisafe() and srcu_read_unlock_nmisafe() Paul E. McKenney
2022-10-02 15:55 ` Frederic Weisbecker
2022-10-02 15:57 ` Frederic Weisbecker
2022-10-02 16:10 ` Paul E. McKenney
2022-10-02 16:09 ` Paul E. McKenney
2022-10-02 21:47 ` Frederic Weisbecker
2022-10-02 23:46 ` Paul E. McKenney
2022-10-03 9:55 ` Frederic Weisbecker
2022-10-03 11:52 ` Paul E. McKenney
2022-10-18 14:31 ` John Ogness
2022-10-18 15:18 ` Paul E. McKenney
2022-09-29 18:07 ` [PATCH RFC v2 rcu 3/8] srcu: Check for consistent per-CPU per-srcu_struct NMI safety Paul E. McKenney
2022-10-02 22:06 ` Frederic Weisbecker
2022-10-02 23:51 ` Paul E. McKenney
2022-10-03 10:13 ` Frederic Weisbecker
2022-10-03 11:57 ` Paul E. McKenney
2022-10-03 12:37 ` Frederic Weisbecker
2022-10-03 13:32 ` Paul E. McKenney
2022-10-03 13:36 ` Frederic Weisbecker
2022-09-29 18:07 ` [PATCH RFC v2 rcu 4/8] srcu: Check for consistent global " Paul E. McKenney
2022-09-29 18:07 ` [PATCH RFC v2 rcu 5/8] arch/x86: Add ARCH_HAS_NMI_SAFE_THIS_CPU_OPS Kconfig option Paul E. McKenney
2022-09-29 18:07 ` [PATCH RFC v2 rcu 6/8] arch/arm64: " Paul E. McKenney
2022-10-05 11:12 ` Mark Rutland [this message]
2022-09-29 18:07 ` [PATCH RFC v2 rcu 7/8] arch/loongarch: " Paul E. McKenney
2022-09-29 18:07 ` [PATCH RFC v2 rcu 8/8] arch/s390: " Paul E. McKenney
2022-10-03 14:11 ` [PATCH v2 rcu 0/8] NMI-safe SRCU reader API Frederic Weisbecker
2022-10-03 16:38 ` Paul E. McKenney
2022-10-14 22:47 ` Joel Fernandes
2022-10-14 22:52 ` Joel Fernandes
2022-10-18 10:33 ` John Ogness
2022-10-18 15:24 ` Paul E. McKenney
2022-10-18 18:44 ` John Ogness
2022-10-18 18:59 ` Paul E. McKenney
2022-10-18 21:57 ` Paul E. McKenney
2022-10-19 11:13 ` John Ogness
2022-10-19 19:14 ` Paul E. McKenney
2022-10-19 21:38 ` John Ogness
2022-10-19 22:05 ` Frederic Weisbecker
2022-10-20 22:27 ` Paul E. McKenney
2022-10-20 22:41 ` Paul E. McKenney
2022-10-21 12:27 ` John Ogness
2022-10-21 13:59 ` Paul E. McKenney
2022-10-21 18:41 ` Paul E. McKenney
2022-10-24 6:15 ` John Ogness
2022-10-24 13:47 ` Paul E. McKenney
2022-10-27 9:31 ` John Ogness
2022-10-27 14:10 ` Paul E. McKenney
2022-10-27 14:39 ` John Ogness
2022-10-27 16:01 ` Paul E. McKenney
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