From febdbfe8a91ce0d11939d4940b592eb0dba8d663 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 6 Feb 2014 18:16:07 +0100 Subject: [PATCH] arch: Prepare for smp_mb__{before,after}_atomic() Since the smp_mb__{before,after}*() ops are fundamentally dependent on how an arch can implement atomics it doesn't make sense to have 3 variants of them. They must all be the same. Furthermore, the 3 variants suggest they're only valid for those 3 atomic ops, while we have many more where they could be applied. So move away from smp_mb__{before,after}_{atomic,clear}_{dec,inc,bit}() and reduce the interface to just the two: smp_mb__{before,after}_atomic(). This patch prepares the way by introducing default implementations in asm-generic/barrier.h that default to a full barrier and providing __deprecated inlines for the previous 6 barriers if they're not provided by the arch. This should allow for a mostly painless transition (lots of deprecated warns in the interim). Signed-off-by: Peter Zijlstra Acked-by: Paul E. McKenney Link: http://lkml.kernel.org/n/tip-wr59327qdyi9mbzn6x937s4e@git.kernel.org Cc: Arnd Bergmann Cc: "Chen, Gong" Cc: John Sullivan Cc: Linus Torvalds Cc: Mauro Carvalho Chehab Cc: Srinivas Pandruvada Cc: "Theodore Ts'o" Cc: linux-arch@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar --- include/asm-generic/atomic.h | 7 +------ include/asm-generic/barrier.h | 8 ++++++++ include/asm-generic/bitops.h | 9 +-------- include/linux/atomic.h | 36 +++++++++++++++++++++++++++++++++++ include/linux/bitops.h | 20 +++++++++++++++++++ kernel/sched/core.c | 16 ++++++++++++++++ 6 files changed, 82 insertions(+), 14 deletions(-) diff --git a/include/asm-generic/atomic.h b/include/asm-generic/atomic.h index 33bd2de3bc1e..9c79e7603459 100644 --- a/include/asm-generic/atomic.h +++ b/include/asm-generic/atomic.h @@ -16,6 +16,7 @@ #define __ASM_GENERIC_ATOMIC_H #include +#include #ifdef CONFIG_SMP /* Force people to define core atomics */ @@ -182,11 +183,5 @@ static inline void atomic_set_mask(unsigned int mask, atomic_t *v) } #endif -/* Assume that atomic operations are already serializing */ -#define smp_mb__before_atomic_dec() barrier() -#define smp_mb__after_atomic_dec() barrier() -#define smp_mb__before_atomic_inc() barrier() -#define smp_mb__after_atomic_inc() barrier() - #endif /* __KERNEL__ */ #endif /* __ASM_GENERIC_ATOMIC_H */ diff --git a/include/asm-generic/barrier.h b/include/asm-generic/barrier.h index 6f692f8ac664..1402fa855388 100644 --- a/include/asm-generic/barrier.h +++ b/include/asm-generic/barrier.h @@ -62,6 +62,14 @@ #define set_mb(var, value) do { (var) = (value); mb(); } while (0) #endif +#ifndef smp_mb__before_atomic +#define smp_mb__before_atomic() smp_mb() +#endif + +#ifndef smp_mb__after_atomic +#define smp_mb__after_atomic() smp_mb() +#endif + #define smp_store_release(p, v) \ do { \ compiletime_assert_atomic_type(*p); \ diff --git a/include/asm-generic/bitops.h b/include/asm-generic/bitops.h index 280ca7a96f75..dcdcacf2fd2b 100644 --- a/include/asm-generic/bitops.h +++ b/include/asm-generic/bitops.h @@ -11,14 +11,7 @@ #include #include - -/* - * clear_bit may not imply a memory barrier - */ -#ifndef smp_mb__before_clear_bit -#define smp_mb__before_clear_bit() smp_mb() -#define smp_mb__after_clear_bit() smp_mb() -#endif +#include #include #include diff --git a/include/linux/atomic.h b/include/linux/atomic.h index 5b08a8540ecf..fef3a809e7cf 100644 --- a/include/linux/atomic.h +++ b/include/linux/atomic.h @@ -3,6 +3,42 @@ #define _LINUX_ATOMIC_H #include +/* + * Provide __deprecated wrappers for the new interface, avoid flag day changes. + * We need the ugly external functions to break header recursion hell. + */ +#ifndef smp_mb__before_atomic_inc +static inline void __deprecated smp_mb__before_atomic_inc(void) +{ + extern void __smp_mb__before_atomic(void); + __smp_mb__before_atomic(); +} +#endif + +#ifndef smp_mb__after_atomic_inc +static inline void __deprecated smp_mb__after_atomic_inc(void) +{ + extern void __smp_mb__after_atomic(void); + __smp_mb__after_atomic(); +} +#endif + +#ifndef smp_mb__before_atomic_dec +static inline void __deprecated smp_mb__before_atomic_dec(void) +{ + extern void __smp_mb__before_atomic(void); + __smp_mb__before_atomic(); +} +#endif + +#ifndef smp_mb__after_atomic_dec +static inline void __deprecated smp_mb__after_atomic_dec(void) +{ + extern void __smp_mb__after_atomic(void); + __smp_mb__after_atomic(); +} +#endif + /** * atomic_add_unless - add unless the number is already a given value * @v: pointer of type atomic_t diff --git a/include/linux/bitops.h b/include/linux/bitops.h index be5fd38bd5a0..cbc5833fb221 100644 --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -32,6 +32,26 @@ extern unsigned long __sw_hweight64(__u64 w); */ #include +/* + * Provide __deprecated wrappers for the new interface, avoid flag day changes. + * We need the ugly external functions to break header recursion hell. + */ +#ifndef smp_mb__before_clear_bit +static inline void __deprecated smp_mb__before_clear_bit(void) +{ + extern void __smp_mb__before_atomic(void); + __smp_mb__before_atomic(); +} +#endif + +#ifndef smp_mb__after_clear_bit +static inline void __deprecated smp_mb__after_clear_bit(void) +{ + extern void __smp_mb__after_atomic(void); + __smp_mb__after_atomic(); +} +#endif + #define for_each_set_bit(bit, addr, size) \ for ((bit) = find_first_bit((addr), (size)); \ (bit) < (size); \ diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 268a45ea238c..8a70ec091760 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -90,6 +90,22 @@ #define CREATE_TRACE_POINTS #include +#ifdef smp_mb__before_atomic +void __smp_mb__before_atomic(void) +{ + smp_mb__before_atomic(); +} +EXPORT_SYMBOL(__smp_mb__before_atomic); +#endif + +#ifdef smp_mb__after_atomic +void __smp_mb__after_atomic(void) +{ + smp_mb__after_atomic(); +} +EXPORT_SYMBOL(__smp_mb__after_atomic); +#endif + void start_bandwidth_timer(struct hrtimer *period_timer, ktime_t period) { unsigned long delta; -- 2.30.2