linux-kernel - [PATCH v5 1/7] arm64: Add a helper for parking CPUs in a loop

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Message-Id: <1456223505-2955-2-git-send-email-suzuki.poulose@arm.com>
Date:	Tue, 23 Feb 2016 10:31:39 +0000
From:	Suzuki K Poulose <suzuki.poulose@....com>
To:	catalin.marinas@....com
Cc:	will.deacon@....com, mark.rutland@....com,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Suzuki K Poulose <suzuki.poulose@....com>
Subject: [PATCH v5 1/7] arm64: Add a helper for parking CPUs in a loop

Adds a routine which can be used to park CPUs (spinning in kernel)
when they can't be killed.

Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Mark Rutland <mark.rutland@....com>
Acked-by: Will Deacon <will.deacon@....com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
---
 arch/arm64/include/asm/smp.h   |    8 ++++++++
 arch/arm64/kernel/cpufeature.c |    5 +----
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/include/asm/smp.h b/arch/arm64/include/asm/smp.h
index d9c3d6a..53b53a9 100644
--- a/arch/arm64/include/asm/smp.h
+++ b/arch/arm64/include/asm/smp.h
@@ -69,4 +69,12 @@ extern int __cpu_disable(void);
 extern void __cpu_die(unsigned int cpu);
 extern void cpu_die(void);
 
+static inline void cpu_park_loop(void)
+{
+	for (;;) {
+		wfe();
+		wfi();
+	}
+}
+
 #endif /* ifndef __ASM_SMP_H */
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 5c90aa4..cc4a089 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -842,10 +842,7 @@ static void fail_incapable_cpu(char *cap_type,
 	/* Check if we can park ourselves */
 	if (cpu_ops[cpu] && cpu_ops[cpu]->cpu_die)
 		cpu_ops[cpu]->cpu_die(cpu);
-	asm(
-	"1:	wfe\n"
-	"	wfi\n"
-	"	b	1b");
+	cpu_park_loop();
 }
 
 /*
-- 
1.7.9.5