linux-kernel - [PATCH v3 4/4] kernel/smp: fix flush_smp_call_function

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Date:   Tue,  2 Mar 2021 07:28:38 +0100
From:   Juergen Gross <jgross@...e.com>
To:     linux-kernel@...r.kernel.org
Cc:     paulmck@...nel.org, mhocko@...e.com, peterz@...radead.org,
        Juergen Gross <jgross@...e.com>
Subject: [PATCH v3 4/4] kernel/smp: fix flush_smp_call_function_queue() cpu offline detection

The warnings for flushing a logically offline cpu's call_single_queue
are gated by a wrong if statement. It should trigger when there have
been new requests before dequeueing them, not afterwards.

Signed-off-by: Juergen Gross <jgross@...e.com>
---
V3:
- new patch
---
 kernel/smp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/smp.c b/kernel/smp.c
index 1a96691dbf7f..b3077c327b0a 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -581,7 +581,7 @@ static void flush_smp_call_function_queue(bool warn_cpu_offline)
 
 	/* There shouldn't be any pending callbacks on an offline CPU. */
 	if (unlikely(warn_cpu_offline && !cpu_online(smp_processor_id()) &&
-		     !warned && !llist_empty(head))) {
+		     !warned && entry)) {
 		warned = true;
 		WARN(1, "IPI on offline CPU %d\n", smp_processor_id());
 
-- 
2.26.2