From 1f03e8d2919270bd6ef64f39a45ce8df8a9f012a Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Mon, 4 Apr 2016 10:57:12 +0200
Subject: locking/barriers: Replace smp_cond_acquire() with
 smp_cond_load_acquire()

This new form allows using hardware assisted waiting.

Some hardware (ARM64 and x86) allow monitoring an address for changes,
so by providing a pointer we can use this to replace the cpu_relax()
with hardware optimized methods in the future.

Requested-by: Will Deacon <will.deacon@arm.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/smp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'kernel/smp.c')

diff --git a/kernel/smp.c b/kernel/smp.c
index 74165443c240..36552beed397 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -107,7 +107,7 @@ void __init call_function_init(void)
  */
 static __always_inline void csd_lock_wait(struct call_single_data *csd)
 {
-	smp_cond_acquire(!(csd->flags & CSD_FLAG_LOCK));
+	smp_cond_load_acquire(&csd->flags, !(VAL & CSD_FLAG_LOCK));
 }
 
 static __always_inline void csd_lock(struct call_single_data *csd)
-- 
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