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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loongarch@lists.linux.dev, linux-mips@vger.kernel.org,
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linux-s390@vger.kernel.org, linux-sh@vger.kernel.org,
sparclinux@vger.kernel.org, linux-xtensa@linux-xtensa.org,
x86@kernel.org
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: [PATCH v5 6/7] smp: reword smp call IPI comment
Date: Tue, 7 Mar 2023 14:35:57 +0000 [thread overview]
Message-ID: <20230307143558.294354-7-vschneid@redhat.com> (raw)
In-Reply-To: <20230307143558.294354-1-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 93b4386cd3096..821b5986721ac 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -495,9 +495,10 @@ 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
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next prev parent reply other threads:[~2023-03-07 15:12 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-07 14:35 [PATCH v5 0/7] Generic IPI sending tracepoint Valentin Schneider
2023-03-07 14:35 ` [PATCH v5 1/7] trace: Add trace_ipi_send_cpumask() Valentin Schneider
2023-03-22 9:39 ` Peter Zijlstra
2023-03-22 10:30 ` Peter Zijlstra
2023-03-22 11:24 ` Valentin Schneider
2023-03-07 14:35 ` [PATCH v5 2/7] sched, smp: Trace IPIs sent via send_call_function_single_ipi() Valentin Schneider
2023-03-07 14:35 ` [PATCH v5 3/7] smp: Trace IPIs sent via arch_send_call_function_ipi_mask() Valentin Schneider
2023-03-07 14:35 ` [PATCH v5 4/7] irq_work: Trace self-IPIs sent via arch_irq_work_raise() Valentin Schneider
2023-03-07 14:35 ` [PATCH v5 5/7] treewide: Trace IPIs sent via smp_send_reschedule() Valentin Schneider
2023-03-07 14:35 ` Valentin Schneider [this message]
2023-03-07 14:35 ` [PATCH v5 7/7] sched, smp: Trace smp callback causing an IPI Valentin Schneider
2023-03-22 9:53 ` Peter Zijlstra
2023-03-22 12:20 ` Valentin Schneider
2023-03-22 14:04 ` Peter Zijlstra
2023-03-22 17:01 ` Valentin Schneider
2023-03-22 17:22 ` Peter Zijlstra
2023-03-22 18:22 ` Valentin Schneider
2023-03-22 23:14 ` Peter Zijlstra
2023-03-23 16:25 ` Valentin Schneider
2023-03-23 17:41 ` Peter Zijlstra
2023-03-23 18:31 ` Valentin Schneider
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