From: Matthew Wilcox <willy@infradead.org>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: rcu@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel-team@meta.com, rostedt@goodmis.org,
Jonathan Corbet <corbet@lwn.net>,
Peter Zijlstra <peterz@infradead.org>,
Mark Rutland <mark.rutland@arm.com>,
Boqun Feng <boqun.feng@gmail.com>,
linux-doc@vger.kernel.org
Subject: Re: [PATCH rcu 2/7] docs: Improve discussion of this_cpu_ptr(), add raw_cpu_ptr()
Date: Thu, 16 Jan 2025 21:02:16 +0000 [thread overview]
Message-ID: <Z4lz2CC7SLgSp90y@casper.infradead.org> (raw)
In-Reply-To: <20250116200239.3782374-2-paulmck@kernel.org>
On Thu, Jan 16, 2025 at 12:02:34PM -0800, Paul E. McKenney wrote:
> +The special cases where it makes sense do obtain a per-CPU pointer in
s/do/to/
> +preemptible code are addressed by raw_cpu_ptr(), but please note that such
s/please note that //
> +use cases need to handle cases where two different CPUs are accessing
> +the same per cpu variable, which might well be that of a third CPU.
> +These use cases are typically performance optimizations. For example,
> +SRCU implements a pair of counters as a pair of per-CPU variables,
> +and rcu_read_lock_nmisafe() uses raw_cpu_ptr() to get a pointer to some
> +CPU's counter, and uses atomic_inc_long() to handle migration between
> +the raw_cpu_ptr() and the atomic_inc_long().
next prev parent reply other threads:[~2025-01-16 21:02 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-01-16 20:02 [PATCH rcu 0/7] Documentation upates Paul E. McKenney
2025-01-16 20:02 ` [PATCH rcu 1/7] doc: Add broken-timing possibility to stallwarn.rst Paul E. McKenney
2025-01-16 20:02 ` [PATCH rcu 2/7] docs: Improve discussion of this_cpu_ptr(), add raw_cpu_ptr() Paul E. McKenney
2025-01-16 21:02 ` Matthew Wilcox [this message]
2025-01-16 22:57 ` Paul E. McKenney
2025-01-16 20:02 ` [PATCH rcu 3/7] rcu: Document self-propagating callbacks Paul E. McKenney
2025-01-16 21:38 ` Jens Axboe
2025-01-16 20:02 ` [PATCH rcu 4/7] srcu: Point call_srcu() to call_rcu() for detailed memory ordering Paul E. McKenney
2025-01-16 20:02 ` [PATCH rcu 5/7] rcu: Add CONFIG_RCU_LAZY delays to call_rcu() kernel-doc header Paul E. McKenney
2025-01-16 20:02 ` [PATCH rcu 6/7] rcu: Clarify RCU_LAZY and RCU_LAZY_DEFAULT_OFF help text Paul E. McKenney
2025-01-16 20:02 ` [PATCH rcu 7/7] rcu: Remove references to old grace-period-wait primitives Paul E. McKenney
2025-01-30 18:47 ` [PATCH rcu 0/7] Documentation upates Paul E. McKenney
2025-01-30 18:49 ` [PATCH rcu v2 1/7] doc: Add broken-timing possibility to stallwarn.rst Paul E. McKenney
2025-01-30 18:49 ` [PATCH rcu v2 2/7] docs: Improve discussion of this_cpu_ptr(), add raw_cpu_ptr() Paul E. McKenney
2025-01-30 18:49 ` [PATCH rcu v2 3/7] rcu: Document self-propagating callbacks Paul E. McKenney
2025-01-30 18:49 ` [PATCH rcu v2 4/7] srcu: Point call_srcu() to call_rcu() for detailed memory ordering Paul E. McKenney
2025-01-30 18:49 ` [PATCH rcu v2 5/7] rcu: Add CONFIG_RCU_LAZY delays to call_rcu() kernel-doc header Paul E. McKenney
2025-01-30 18:49 ` [PATCH rcu v2 6/7] rcu: Clarify RCU_LAZY and RCU_LAZY_DEFAULT_OFF help text Paul E. McKenney
2025-01-30 18:49 ` [PATCH rcu v2 7/7] rcu: Remove references to old grace-period-wait primitives Paul E. McKenney
-- strict thread matches above, loose matches on Subject: below --
2025-02-18 5:45 [PATCH rcu 0/7] RCU documentation changes for v6.15 Boqun Feng
2025-02-18 5:45 ` [PATCH rcu 2/7] docs: Improve discussion of this_cpu_ptr(), add raw_cpu_ptr() Boqun Feng
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