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From:   Valentin Schneider <vschneid@redhat.com>
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Subject: [RFC PATCH v2 7/8] smp: reword smp call IPI comment
Date:   Wed,  2 Nov 2022 18:33:35 +0000
Message-Id: <20221102183336.3120536-6-vschneid@redhat.com>
In-Reply-To: <20221102182949.3119584-1-vschneid@redhat.com>
References: <20221102182949.3119584-1-vschneid@redhat.com>
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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