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Date:   Tue, 10 Aug 2021 19:30:56 +0200
From:   Greg Kroah-Hartman <>
Cc:     Greg Kroah-Hartman <>,, Prarit Bhargava <>,
        Richard Henderson <>,
        Ivan Kokshaysky <>,
        Matt Turner <>,
        Sasha Levin <>
Subject: [PATCH 5.4 83/85] alpha: Send stop IPI to send to online CPUs

From: Prarit Bhargava <>

[ Upstream commit caace6ca4e06f09413fb8f8a63319594cfb7d47d ]

This issue was noticed while debugging a shutdown issue where some
secondary CPUs are not being shutdown correctly.  A fix for that [1] requires
that secondary cpus be offlined using the cpu_online_mask so that the
stop operation is a no-op if CPU HOTPLUG is disabled.  I, like the author in
[1] looked at the architectures and found that alpha is one of two
architectures that executes smp_send_stop() on all possible CPUs.

On alpha, smp_send_stop() sends an IPI to all possible CPUs but only needs
to send them to online CPUs.

Send the stop IPI to only the online CPUs.


Signed-off-by: Prarit Bhargava <>
Cc: Richard Henderson <>
Cc: Ivan Kokshaysky <>
Signed-off-by: Matt Turner <>
Signed-off-by: Sasha Levin <>
 arch/alpha/kernel/smp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/alpha/kernel/smp.c b/arch/alpha/kernel/smp.c
index 5f90df30be20..06fd42417aa9 100644
--- a/arch/alpha/kernel/smp.c
+++ b/arch/alpha/kernel/smp.c
@@ -585,7 +585,7 @@ void
 	cpumask_t to_whom;
-	cpumask_copy(&to_whom, cpu_possible_mask);
+	cpumask_copy(&to_whom, cpu_online_mask);
 	cpumask_clear_cpu(smp_processor_id(), &to_whom);
 	if (hard_smp_processor_id() != boot_cpu_id)

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