Commit 54988727 authored by Will Deacon's avatar Will Deacon
Browse files

locking/barriers: Use '__unqual_scalar_typeof' for load-acquire macros 



Passing volatile-qualified pointers to the asm-generic implementations of
the load-acquire macros results in a re-load from the stack due to the
temporary result variable inheriting the volatile semantics thanks to the
use of 'typeof()'.

Define these temporary variables using 'unqual_scalar_typeof' to drop
the volatile qualifier in the case that they are scalar types.

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent dee081bf

include/asm-generic/barrier.h

+8 −8
Original line number Diff line number Diff line
@@ -128,10 +128,10 @@ do { \ 
#ifndef __smp_load_acquire

#define __smp_load_acquire(p)						\

({									\

	typeof(*p) ___p1 = READ_ONCE(*p);				\

	__unqual_scalar_typeof(*p) ___p1 = READ_ONCE(*p);		\

	compiletime_assert_atomic_type(*p);				\

	__smp_mb();							\

	___p1;								\

	(typeof(*p))___p1;						\

})

#endif
@@ -183,10 +183,10 @@ do { \ 
#ifndef smp_load_acquire

#define smp_load_acquire(p)						\

({									\

	typeof(*p) ___p1 = READ_ONCE(*p);				\

	__unqual_scalar_typeof(*p) ___p1 = READ_ONCE(*p);		\

	compiletime_assert_atomic_type(*p);				\

	barrier();							\

	___p1;								\

	(typeof(*p))___p1;						\

})

#endif
@@ -229,14 +229,14 @@ do { \ 
#ifndef smp_cond_load_relaxed

#define smp_cond_load_relaxed(ptr, cond_expr) ({		\

	typeof(ptr) __PTR = (ptr);				\

	typeof(*ptr) VAL;					\

	__unqual_scalar_typeof(*ptr) VAL;			\

	for (;;) {						\

		VAL = READ_ONCE(*__PTR);			\

		if (cond_expr)					\

			break;					\

		cpu_relax();					\

	}							\

	VAL;							\

	(typeof(*ptr))VAL;					\

})

#endif
@@ -250,10 +250,10 @@ do { \ 
 */

#ifndef smp_cond_load_acquire

#define smp_cond_load_acquire(ptr, cond_expr) ({		\

	typeof(*ptr) _val;					\

	__unqual_scalar_typeof(*ptr) _val;			\

	_val = smp_cond_load_relaxed(ptr, cond_expr);		\

	smp_acquire__after_ctrl_dep();				\

	_val;							\

	(typeof(*ptr))_val;					\

})

#endif

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