From: Prarit Bhargava prarit@redhat.com
[ 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.
[1] https://lkml.org/lkml/2020/1/10/250
Signed-off-by: Prarit Bhargava prarit@redhat.com Cc: Richard Henderson rth@twiddle.net Cc: Ivan Kokshaysky ink@jurassic.park.msu.ru Signed-off-by: Matt Turner mattst88@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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 smp_send_stop(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); #ifdef DEBUG_IPI_MSG if (hard_smp_processor_id() != boot_cpu_id)