Commit 62e8a325 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

atomic, arch: Audit atomic_{read,set}() 



This patch makes sure that atomic_{read,set}() are at least
{READ,WRITE}_ONCE().

We already had the 'requirement' that atomic_read() should use
ACCESS_ONCE(), and most archs had this, but a few were lacking.
All are now converted to use READ_ONCE().

And, by a symmetry and general paranoia argument, upgrade atomic_set()
to use WRITE_ONCE().

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: james.hogan@imgtec.com
Cc: linux-kernel@vger.kernel.org
Cc: oleg@redhat.com
Cc: will.deacon@arm.com
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 90fe6514

arch/alpha/include/asm/atomic.h

+4 −4
Original line number Diff line number Diff line
@@ -17,11 +17,11 @@ 
#define ATOMIC_INIT(i)		{ (i) }

#define ATOMIC64_INIT(i)	{ (i) }



#define atomic_read(v)		ACCESS_ONCE((v)->counter)

#define atomic64_read(v)	ACCESS_ONCE((v)->counter)

#define atomic_read(v)		READ_ONCE((v)->counter)

#define atomic64_read(v)	READ_ONCE((v)->counter)



#define atomic_set(v,i)		((v)->counter = (i))

#define atomic64_set(v,i)	((v)->counter = (i))

#define atomic_set(v,i)		WRITE_ONCE((v)->counter, (i))

#define atomic64_set(v,i)	WRITE_ONCE((v)->counter, (i))



/*

 * To get proper branch prediction for the main line, we must branch

arch/arc/include/asm/atomic.h

+4 −4
Original line number Diff line number Diff line
@@ -17,11 +17,11 @@ 
#include <asm/barrier.h>

#include <asm/smp.h>



#define atomic_read(v)  ((v)->counter)

#define atomic_read(v)  READ_ONCE((v)->counter)



#ifdef CONFIG_ARC_HAS_LLSC



#define atomic_set(v, i) (((v)->counter) = (i))

#define atomic_set(v, i) WRITE_ONCE(((v)->counter), (i))



#ifdef CONFIG_ARC_STAR_9000923308
@@ -107,7 +107,7 @@ static inline int atomic_##op##_return(int i, atomic_t *v) \ 
#ifndef CONFIG_SMP



 /* violating atomic_xxx API locking protocol in UP for optimization sake */

#define atomic_set(v, i) (((v)->counter) = (i))

#define atomic_set(v, i) WRITE_ONCE(((v)->counter), (i))



#else
@@ -125,7 +125,7 @@ static inline void atomic_set(atomic_t *v, int i) 
	unsigned long flags;



	atomic_ops_lock(flags);

	v->counter = i;

	WRITE_ONCE(v->counter, i);

	atomic_ops_unlock(flags);

}

arch/arm/include/asm/atomic.h

+2 −2
Original line number Diff line number Diff line
@@ -27,8 +27,8 @@ 
 * strex/ldrex monitor on some implementations. The reason we can use it for

 * atomic_set() is the clrex or dummy strex done on every exception return.

 */

#define atomic_read(v)	ACCESS_ONCE((v)->counter)

#define atomic_set(v,i)	(((v)->counter) = (i))

#define atomic_read(v)	READ_ONCE((v)->counter)

#define atomic_set(v,i)	WRITE_ONCE(((v)->counter), (i))



#if __LINUX_ARM_ARCH__ >= 6

arch/arm64/include/asm/atomic.h

+1 −1
Original line number Diff line number Diff line
@@ -54,7 +54,7 @@ 
#define ATOMIC_INIT(i)	{ (i) }



#define atomic_read(v)			READ_ONCE((v)->counter)

#define atomic_set(v, i)		(((v)->counter) = (i))

#define atomic_set(v, i)		WRITE_ONCE(((v)->counter), (i))

#define atomic_xchg(v, new)		xchg(&((v)->counter), (new))

#define atomic_cmpxchg(v, old, new)	cmpxchg(&((v)->counter), (old), (new))

arch/avr32/include/asm/atomic.h

+2 −2
Original line number Diff line number Diff line
@@ -19,8 +19,8 @@ 


#define ATOMIC_INIT(i)  { (i) }



#define atomic_read(v)		ACCESS_ONCE((v)->counter)

#define atomic_set(v, i)	(((v)->counter) = i)

#define atomic_read(v)		READ_ONCE((v)->counter)

#define atomic_set(v, i)	WRITE_ONCE(((v)->counter), (i))



#define ATOMIC_OP_RETURN(op, asm_op, asm_con)				\

static inline int __atomic_##op##_return(int i, atomic_t *v)		\

CRA Git | Maintained and supported by SUSTech CRA and CCSE