[PATCH 6.3 06/29] x86/smp: Remove pointless wmb()s from native_stop_other_cpus()

Greg Kroah-Hartman
2023-06-29T18:47:07Z

From: Thomas Gleixner <tglx@linutronix.de>

commit 2affa6d6db28855e6340b060b809c23477aa546e upstream.

The wmb()s before sending the IPIs are not synchronizing anything.

If at all then the apic IPI functions have to provide or act as appropriate
barriers.

Remove these cargo cult barriers which have no explanation of what they are
synchronizing.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20230615193330.378358382@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/kernel/smp.c | 6 ------
1 file changed, 6 deletions(-)

--- a/arch/x86/kernel/smp.c
+++ b/arch/x86/kernel/smp.c
@@ -184,9 +184,6 @@ static void native_stop_other_cpus(int w
cpumask_clear_cpu(cpu, &cpus_stop_mask);

if (!cpumask_empty(&cpus_stop_mask)) {
- /* sync above data before sending IRQ */
- wmb();
-
apic_send_IPI_allbutself(REBOOT_VECTOR);

/*
@@ -208,9 +205,6 @@ static void native_stop_other_cpus(int w
* CPUs to stop.
*/
if (!smp_no_nmi_ipi && !register_stop_handler()) {
- /* Sync above data before sending IRQ */
- wmb();
-
pr_emerg("Shutting down cpus with NMI\n");

for_each_cpu(cpu, &cpus_stop_mask)