[PATCH 3/4] smp: get this_cpu once in smp_call_function

[Shrikanth Hegde]

Calling smp_processor_id() on:
- In CONFIG_DEBUG_PREEMPT=y, if preemption/irq is disabled, then it does
not print any warning.
- In CONFIG_DEBUG_PREEMPT=n, it doesn't do anything apart from getting
__smp_processor_id

So with both CONFIG_DEBUG_PREEMPT=y/n, in preemption disabled section
it is better to cache the value. It could save a few cycles. Though
tiny, repeated in loop could add up to a small value.

smp_call_function_single/smp_call_function_many_cond is called with
preemption disabled.
So cache the values once.

Signed-off-by: Shrikanth Hegde <sshegde@xxxxxxxxxxxxx>
---
 kernel/smp.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/smp.c b/kernel/smp.c
index f349960f79ca..4c57104d1cd3 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -677,7 +677,7 @@ int smp_call_function_single(int cpu, smp_call_func_t func, void *info,
 	csd->func = func;
 	csd->info = info;
 #ifdef CONFIG_CSD_LOCK_WAIT_DEBUG
-	csd->node.src = smp_processor_id();
+	csd->node.src = this_cpu;
 	csd->node.dst = cpu;
 #endif
 
@@ -832,7 +832,7 @@ static void smp_call_function_many_cond(const struct cpumask *mask,
 			csd->func = func;
 			csd->info = info;
 #ifdef CONFIG_CSD_LOCK_WAIT_DEBUG
-			csd->node.src = smp_processor_id();
+			csd->node.src = this_cpu;
 			csd->node.dst = cpu;
 #endif
 			trace_csd_queue_cpu(cpu, _RET_IP_, func, csd);
-- 
2.47.3