x86/smp: Move the call to smp_processor_id() after the early exit in native_stop_othe...

Improve code generation in native_stop_other_cpus() a tiny bit:
smp_processor_id() accesses a per-CPU variable, so the compiler
is not able to move the call after the early exit on its own.

Also rename the "cpu" variable to a more descriptive "this_cpu", and
use 'cpu' as a separate iterator variable later in the function.

No functional change intended.

Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20231123203605.3474745-1-ubizjak@gmail.com

diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c
index 6eb06d001bcc648bc3cdbb71f6e5a9c896d6d1c8..65dd44e3fc1cfaf5cc8728624af6b3fbed47f8a1 100644 (file)
--- a/arch/x86/kernel/smp.c
+++ b/arch/x86/kernel/smp.c
@@ -148,14 +148,15 @@ static int register_stop_handler(void)
 
 static void native_stop_other_cpus(int wait)
 {
-       unsigned int cpu = smp_processor_id();
+       unsigned int this_cpu;
        unsigned long flags, timeout;
 
        if (reboot_force)
                return;
 
        /* Only proceed if this is the first CPU to reach this code */
-       if (atomic_cmpxchg(&stopping_cpu, -1, cpu) != -1)
+       this_cpu = smp_processor_id();
+       if (atomic_cmpxchg(&stopping_cpu, -1, this_cpu) != -1)
                return;
 
        /* For kexec, ensure that offline CPUs are out of MWAIT and in HLT */
@@ -190,7 +191,7 @@ static void native_stop_other_cpus(int wait)
         * NMIs.
         */
        cpumask_copy(&cpus_stop_mask, cpu_online_mask);
-       cpumask_clear_cpu(cpu, &cpus_stop_mask);
+       cpumask_clear_cpu(this_cpu, &cpus_stop_mask);
 
        if (!cpumask_empty(&cpus_stop_mask)) {
                apic_send_IPI_allbutself(REBOOT_VECTOR);
@@ -234,6 +235,8 @@ static void native_stop_other_cpus(int wait)
                 * CPUs to stop.
                 */
                if (!smp_no_nmi_ipi && !register_stop_handler()) {
+                       unsigned int cpu;
+
                        pr_emerg("Shutting down cpus with NMI\n");
 
                        for_each_cpu(cpu, &cpus_stop_mask)