linux-kernel - [PATCH v2] s390/cpum_cf: Remove superfluous SMP function call

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Message-Id: <1462179572-54920-1-git-send-email-anna-maria@linutronix.de>
Date:	Mon,  2 May 2016 10:59:32 +0200
From:	Anna-Maria Gleixner <anna-maria@...utronix.de>
To:	linux-kernel@...r.kernel.org
Cc:	rt@...utronix.de, Anna-Maria Gleixner <anna-maria@...utronix.de>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	linux-s390@...r.kernel.org
Subject: [PATCH v2] s390/cpum_cf: Remove superfluous SMP function call

Since commit 3b9d6da67e11 ("cpu/hotplug: Fix rollback during error-out
in __cpu_disable()") it is ensured that callbacks of CPU_ONLINE and
CPU_DOWN_PREPARE are processed on the hotplugged CPU. Due to this SMP
function calls are no longer required.

Replace smp_call_function_single() with a direct call of
setup_pmc_cpu(). To keep the calling convention, interrupts are
explicitly disabled around the call.

Cc: Martin Schwidefsky <schwidefsky@...ibm.com>
Cc: Heiko Carstens <heiko.carstens@...ibm.com>
Cc: linux-s390@...r.kernel.org
Signed-off-by: Anna-Maria Gleixner <anna-maria@...utronix.de>
---
Changes in v2:
	- Adapt referenced commit in commit message

 arch/s390/kernel/perf_cpum_cf.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- a/arch/s390/kernel/perf_cpum_cf.c
+++ b/arch/s390/kernel/perf_cpum_cf.c
@@ -665,18 +665,21 @@ static struct pmu cpumf_pmu = {
 static int cpumf_pmu_notifier(struct notifier_block *self, unsigned long action,
 			      void *hcpu)
 {
-	unsigned int cpu = (long) hcpu;
 	int flags;
 
 	switch (action & ~CPU_TASKS_FROZEN) {
 	case CPU_ONLINE:
 	case CPU_DOWN_FAILED:
 		flags = PMC_INIT;
-		smp_call_function_single(cpu, setup_pmc_cpu, &flags, 1);
+		local_irq_disable();
+		setup_pmc_cpu(&flags);
+		local_irq_enable();
 		break;
 	case CPU_DOWN_PREPARE:
 		flags = PMC_RELEASE;
-		smp_call_function_single(cpu, setup_pmc_cpu, &flags, 1);
+		local_irq_disable();
+		setup_pmc_cpu(&flags);
+		local_irq_enable();
 		break;
 	default:
 		break;