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

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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
This commit is contained in:
Uros Bizjak
2023-11-23 21:34:22 +01:00
committed by Ingo Molnar
parent 4604c052b8
commit 9d1c8f2153
1 changed files with 6 additions and 3 deletions
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9
arch/x86/kernel/smp.c
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@@ -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)