From: Valentin Schneider <vschneid@redhat.com>
To: linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-snps-arc@lists.infradead.org,
linux-arm-kernel@lists.infradead.org, linux-csky@vger.kernel.org,
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Cc: "Paul E. McKenney" <paulmck@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Juri Lelli <juri.lelli@redhat.com>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
Frederic Weisbecker <frederic@kernel.org>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>, Marc Zyngier <maz@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Russell King <linux@armlinux.org.uk>,
Nicholas Piggin <npiggin@gmail.com>, Guo Ren <guoren@kernel.org>,
"David S. Miller" <davem@davemloft.net>
Subject: [RFC PATCH v2 7/8] smp: reword smp call IPI comment
Date: Wed, 2 Nov 2022 18:33:35 +0000 [thread overview]
Message-ID: <20221102183336.3120536-6-vschneid@redhat.com> (raw)
In-Reply-To: <20221102182949.3119584-1-vschneid@redhat.com>
Accessing the call_single_queue hasn't involved a spinlock since 2014:
6897fc22ea01 ("kernel: use lockless list for smp_call_function_single")
The llist operations (namely cmpxchg() and xchg()) provide similar ordering
guarantees, update the comment to lessen confusion.
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
---
kernel/smp.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/kernel/smp.c b/kernel/smp.c
index 44fa4b9b1f46b..b96579fe08f09 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -503,9 +503,10 @@ void __smp_call_single_queue(int cpu, struct llist_node *node)
#endif
/*
- * The list addition should be visible before sending the IPI
- * handler locks the list to pull the entry off it because of
- * normal cache coherency rules implied by spinlocks.
+ * The list addition should be visible to the target CPU when it pops
+ * the head of the list to pull the entry off it in the IPI handler
+ * because of normal cache coherency rules implied by the underlying
+ * llist ops.
*
* If IPIs can go out of order to the cache coherency protocol
* in an architecture, sufficient synchronisation should be added
--
2.31.1
next prev parent reply other threads:[~2022-11-02 18:37 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-02 18:29 [RFC PATCH v2 0/8] Generic IPI sending tracepoint Valentin Schneider
2022-11-02 18:29 ` [RFC PATCH v2 1/8] DO-NOT-MERGE: tracing: Add __cpumask to denote a trace event field that is a cpumask_t Valentin Schneider
2022-11-02 18:33 ` [RFC PATCH v2 2/8] trace: Add trace_ipi_send_cpumask() Valentin Schneider
2022-11-02 18:33 ` [RFC PATCH v2 3/8] sched, smp: Trace IPIs sent via send_call_function_single_ipi() Valentin Schneider
2022-11-02 18:33 ` [RFC PATCH v2 4/8] smp: Trace IPIs sent via arch_send_call_function_ipi_mask() Valentin Schneider
2022-11-17 9:08 ` Peter Zijlstra
2022-11-17 14:23 ` Valentin Schneider
2022-11-02 18:33 ` [RFC PATCH v2 5/8] irq_work: Trace self-IPIs sent via arch_irq_work_raise() Valentin Schneider
2022-11-17 9:10 ` Peter Zijlstra
2022-11-02 18:33 ` [RFC PATCH v2 6/8] treewide: Trace IPIs sent via smp_send_reschedule() Valentin Schneider
2022-11-17 9:12 ` Peter Zijlstra
2022-11-17 14:24 ` Valentin Schneider
2022-11-02 18:33 ` Valentin Schneider [this message]
2022-11-02 18:33 ` [RFC PATCH v2 8/8] sched, smp: Trace smp callback causing an IPI Valentin Schneider
2022-11-17 14:12 ` Peter Zijlstra
2022-11-17 14:45 ` Valentin Schneider
2022-11-18 9:12 ` Peter Zijlstra
2022-11-18 16:42 ` Daniel Bristot de Oliveira
2022-11-14 17:27 ` [RFC PATCH v2 0/8] Generic IPI sending tracepoint Steven Rostedt
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