[PATCH RT 4/8] mm: page_alloc: Use local_lock_on() instead of plain spinlock

[Steven Rostedt]

From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

The plain spinlock while sufficient does not update the local_lock
internals. Use a proper local_lock function instead to ease debugging.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: stable-rt@xxxxxxxxxxxxxxx
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
 include/linux/locallock.h |   11 +++++++++++
 mm/page_alloc.c           |    4 ++--
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/include/linux/locallock.h b/include/linux/locallock.h
index 0161fbb..f1804a3 100644
--- a/include/linux/locallock.h
+++ b/include/linux/locallock.h
@@ -137,6 +137,12 @@ static inline int __local_lock_irqsave(struct local_irq_lock *lv)
 		_flags = __get_cpu_var(lvar).flags;			\
 	} while (0)
 
+#define local_lock_irqsave_on(lvar, _flags, cpu)			\
+	do {								\
+		__local_lock_irqsave(&per_cpu(lvar, cpu));		\
+		_flags = per_cpu(lvar, cpu).flags;			\
+	} while (0)
+
 static inline int __local_unlock_irqrestore(struct local_irq_lock *lv,
 					    unsigned long flags)
 {
@@ -156,6 +162,11 @@ static inline int __local_unlock_irqrestore(struct local_irq_lock *lv,
 			put_local_var(lvar);				\
 	} while (0)
 
+#define local_unlock_irqrestore_on(lvar, flags, cpu)			\
+	do {								\
+		__local_unlock_irqrestore(&per_cpu(lvar, cpu), flags);	\
+	} while (0)
+
 #define local_spin_trylock_irq(lvar, lock)				\
 	({								\
 		int __locked;						\
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e097a56..9be717b 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -221,9 +221,9 @@ static DEFINE_LOCAL_IRQ_LOCK(pa_lock);
 
 #ifdef CONFIG_PREEMPT_RT_BASE
 # define cpu_lock_irqsave(cpu, flags)		\
-	spin_lock_irqsave(&per_cpu(pa_lock, cpu).lock, flags)
+	local_lock_irqsave_on(pa_lock, flags, cpu)
 # define cpu_unlock_irqrestore(cpu, flags)		\
-	spin_unlock_irqrestore(&per_cpu(pa_lock, cpu).lock, flags)
+	local_unlock_irqrestore_on(pa_lock, flags, cpu)
 #else
 # define cpu_lock_irqsave(cpu, flags)		local_irq_save(flags)
 # define cpu_unlock_irqrestore(cpu, flags)	local_irq_restore(flags)
-- 
1.7.10.4


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