X-Git-Url: https://gerrit.opnfv.org/gerrit/gitweb?a=blobdiff_plain;f=kernel%2Farch%2Farm64%2Finclude%2Fasm%2Fspinlock.h;fp=kernel%2Farch%2Farm64%2Finclude%2Fasm%2Fspinlock.h;h=499e8de33a0004c42c170de2fc007d3224908ac3;hb=52f993b8e89487ec9ee15a7fb4979e0f09a45b27;hp=c85e96d174a5fbd4764adb748b9bc11c70479617;hpb=c189ccac5702322ed843fe17057035b7222a59b6;p=kvmfornfv.git

diff --git a/kernel/arch/arm64/include/asm/spinlock.h b/kernel/arch/arm64/include/asm/spinlock.h
index c85e96d17..499e8de33 100644
--- a/kernel/arch/arm64/include/asm/spinlock.h
+++ b/kernel/arch/arm64/include/asm/spinlock.h
@@ -312,4 +312,14 @@ static inline int arch_read_trylock(arch_rwlock_t *rw)
 #define arch_read_relax(lock)	cpu_relax()
 #define arch_write_relax(lock)	cpu_relax()
 
+/*
+ * Accesses appearing in program order before a spin_lock() operation
+ * can be reordered with accesses inside the critical section, by virtue
+ * of arch_spin_lock being constructed using acquire semantics.
+ *
+ * In cases where this is problematic (e.g. try_to_wake_up), an
+ * smp_mb__before_spinlock() can restore the required ordering.
+ */
+#define smp_mb__before_spinlock()	smp_mb()
+
 #endif /* __ASM_SPINLOCK_H */