linux-kernel - csky: smp_mb__after

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Date:   Wed, 5 Aug 2020 12:41:46 +0200
From:   peterz@...radead.org
To:     ren_guo@...ky.com
Cc:     linux-kernel@...r.kernel.org, linux-csky@...r.kernel.org,
        mathieu.desnoyers@...icios.com, Will Deacon <will@...nel.org>
Subject: csky: smp_mb__after_spinlock

Hi,

While doing an audit of smp_mb__after_spinlock, I found that csky
defines it, why?

CSKY only has smp_mb(), it doesn't override __atomic_acquire_fence or
otherwise special cases it's atomic*_acquire() primitives. It has an
explicit smp_mb() in its arch_spin_lock().

---
diff --git a/arch/csky/include/asm/spinlock.h b/arch/csky/include/asm/spinlock.h
index 7cf3f2b34cea..22a05caf2d18 100644
--- a/arch/csky/include/asm/spinlock.h
+++ b/arch/csky/include/asm/spinlock.h
@@ -88,9 +88,6 @@ static inline int arch_spin_is_contended(arch_spinlock_t *lock)
 
 #include <asm/qrwlock.h>
 
-/* See include/linux/spinlock.h */
-#define smp_mb__after_spinlock()	smp_mb()
-
 #else /* CONFIG_QUEUED_RWLOCKS */
 
 /*