linux-kernel - [PATCH] arm64/debug: Remove superfluous SMP function call

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Date:	Mon,  4 Apr 2016 12:42:29 +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>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	linux-arm-kernel@...ts.infradead.or
Subject: [PATCH] arm64/debug: Remove superfluous SMP function call

Since commit 1cf4f629d9d2 "cpu/hotplug: Move online calls to
hotplugged cpu" 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 to
clear_os_lock(). The function writes the OSLAR register to clear OS
locking. This does not require to be called with interrupts disabled,
therefore the smp_call_function_single() calling convention is not
preserved.

Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will.deacon@....com>
Cc: linux-arm-kernel@...ts.infradead.or
Signed-off-by: Anna-Maria Gleixner <anna-maria@...utronix.de>
---
 arch/arm64/kernel/debug-monitors.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/arch/arm64/kernel/debug-monitors.c
+++ b/arch/arm64/kernel/debug-monitors.c
@@ -135,9 +135,8 @@ static void clear_os_lock(void *unused)
 static int os_lock_notify(struct notifier_block *self,
 				    unsigned long action, void *data)
 {
-	int cpu = (unsigned long)data;
 	if ((action & ~CPU_TASKS_FROZEN) == CPU_ONLINE)
-		smp_call_function_single(cpu, clear_os_lock, NULL, 1);
+		clear_os_lock(NULL);
 	return NOTIFY_OK;
 }