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Message-Id: <1522647064-27167-2-git-send-email-rao.shoaib@oracle.com> Date: Sun, 1 Apr 2018 22:31:03 -0700 From: rao.shoaib@...cle.com To: linux-kernel@...r.kernel.org Cc: paulmck@...ux.vnet.ibm.com, joe@...ches.com, willy@...radead.org, brouer@...hat.com, linux-mm@...ck.org, Rao Shoaib <rao.shoaib@...cle.com> Subject: [PATCH 1/2] Move kfree_call_rcu() to slab_common.c From: Rao Shoaib <rao.shoaib@...cle.com> kfree_call_rcu does not belong in linux/rcupdate.h and should be moved to slab_common.c Signed-off-by: Rao Shoaib <rao.shoaib@...cle.com> --- include/linux/rcupdate.h | 43 +++---------------------------------------- include/linux/rcutree.h | 2 -- include/linux/slab.h | 42 ++++++++++++++++++++++++++++++++++++++++++ kernel/rcu/tree.c | 24 ++++++++++-------------- mm/slab_common.c | 10 ++++++++++ 5 files changed, 65 insertions(+), 56 deletions(-) diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 043d047..6338fb6 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -55,6 +55,9 @@ void call_rcu(struct rcu_head *head, rcu_callback_t func); #define call_rcu call_rcu_sched #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ +/* only for use by kfree_call_rcu() */ +void call_rcu_lazy(struct rcu_head *head, rcu_callback_t func); + void call_rcu_bh(struct rcu_head *head, rcu_callback_t func); void call_rcu_sched(struct rcu_head *head, rcu_callback_t func); void synchronize_sched(void); @@ -837,45 +840,6 @@ static inline notrace void rcu_read_unlock_sched_notrace(void) #define __is_kfree_rcu_offset(offset) ((offset) < 4096) /* - * Helper macro for kfree_rcu() to prevent argument-expansion eyestrain. - */ -#define __kfree_rcu(head, offset) \ - do { \ - BUILD_BUG_ON(!__is_kfree_rcu_offset(offset)); \ - kfree_call_rcu(head, (rcu_callback_t)(unsigned long)(offset)); \ - } while (0) - -/** - * kfree_rcu() - kfree an object after a grace period. - * @ptr: pointer to kfree - * @rcu_head: the name of the struct rcu_head within the type of @ptr. - * - * Many rcu callbacks functions just call kfree() on the base structure. - * These functions are trivial, but their size adds up, and furthermore - * when they are used in a kernel module, that module must invoke the - * high-latency rcu_barrier() function at module-unload time. - * - * The kfree_rcu() function handles this issue. Rather than encoding a - * function address in the embedded rcu_head structure, kfree_rcu() instead - * encodes the offset of the rcu_head structure within the base structure. - * Because the functions are not allowed in the low-order 4096 bytes of - * kernel virtual memory, offsets up to 4095 bytes can be accommodated. - * If the offset is larger than 4095 bytes, a compile-time error will - * be generated in __kfree_rcu(). If this error is triggered, you can - * either fall back to use of call_rcu() or rearrange the structure to - * position the rcu_head structure into the first 4096 bytes. - * - * Note that the allowable offset might decrease in the future, for example, - * to allow something like kmem_cache_free_rcu(). - * - * The BUILD_BUG_ON check must not involve any function calls, hence the - * checks are done in macros here. - */ -#define kfree_rcu(ptr, rcu_head) \ - __kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head)) - - -/* * Place this after a lock-acquisition primitive to guarantee that * an UNLOCK+LOCK pair acts as a full barrier. This guarantee applies * if the UNLOCK and LOCK are executed by the same CPU or if the @@ -887,5 +851,4 @@ static inline notrace void rcu_read_unlock_sched_notrace(void) #define smp_mb__after_unlock_lock() do { } while (0) #endif /* #else #ifdef CONFIG_ARCH_WEAK_RELEASE_ACQUIRE */ - #endif /* __LINUX_RCUPDATE_H */ diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index fd996cd..567ef58 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -48,8 +48,6 @@ void synchronize_rcu_bh(void); void synchronize_sched_expedited(void); void synchronize_rcu_expedited(void); -void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func); - /** * synchronize_rcu_bh_expedited - Brute-force RCU-bh grace period * diff --git a/include/linux/slab.h b/include/linux/slab.h index 231abc8..116e870 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -355,6 +355,48 @@ void *__kmalloc(size_t size, gfp_t flags) __assume_kmalloc_alignment __malloc; void *kmem_cache_alloc(struct kmem_cache *, gfp_t flags) __assume_slab_alignment __malloc; void kmem_cache_free(struct kmem_cache *, void *); +void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func); + +/* Helper macro for kfree_rcu() to prevent argument-expansion eyestrain. */ +#define __kfree_rcu(head, offset) \ + do { \ + unsigned long __of = (unsigned long)offset; \ + BUILD_BUG_ON(!__is_kfree_rcu_offset(__of)); \ + kfree_call_rcu(head, (rcu_callback_t)(__of)); \ + } while (0) + +/** + * kfree_rcu() - kfree an object after a grace period. + * @ptr: pointer to kfree + * @rcu_name: the name of the struct rcu_head within the type of @ptr. + * + * Many rcu callbacks functions just call kfree() on the base structure. + * These functions are trivial, but their size adds up, and furthermore + * when they are used in a kernel module, that module must invoke the + * high-latency rcu_barrier() function at module-unload time. + * + * The kfree_rcu() function handles this issue. Rather than encoding a + * function address in the embedded rcu_head structure, kfree_rcu() instead + * encodes the offset of the rcu_head structure within the base structure. + * Because the functions are not allowed in the low-order 4096 bytes of + * kernel virtual memory, offsets up to 4095 bytes can be accommodated. + * If the offset is larger than 4095 bytes, a compile-time error will + * be generated in __kfree_rcu(). If this error is triggered, you can + * either fall back to use of call_rcu() or rearrange the structure to + * position the rcu_head structure into the first 4096 bytes. + * + * Note that the allowable offset might decrease in the future, for example, + * to allow something like kmem_cache_free_rcu(). + * + * The BUILD_BUG_ON check must not involve any function calls, hence the + * checks are done in macros here. + */ +#define kfree_rcu(ptr, rcu_name) \ + do { \ + unsigned long __off = offsetof(typeof(*(ptr)), rcu_name); \ + struct rcu_head *__rptr = (void *)ptr + __off; \ + __kfree_rcu(__rptr, __off); \ + } while (0) /* * Bulk allocation and freeing operations. These are accelerated in an * allocator specific way to avoid taking locks repeatedly or building diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 491bdf3..e40f014 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3101,6 +3101,16 @@ void call_rcu_sched(struct rcu_head *head, rcu_callback_t func) } EXPORT_SYMBOL_GPL(call_rcu_sched); +/* Queue an RCU callback for lazy invocation after a grace period. + * Currently there is no way of tagging the lazy RCU callbacks in the + * list of pending callbacks. Until then, this function may only be + * called from kfree_call_rcu(). + */ +void call_rcu_lazy(struct rcu_head *head, rcu_callback_t func) +{ + __call_rcu(head, func, rcu_state_p, -1, 1); +} + /** * call_rcu_bh() - Queue an RCU for invocation after a quicker grace period. * @head: structure to be used for queueing the RCU updates. @@ -3130,20 +3140,6 @@ void call_rcu_bh(struct rcu_head *head, rcu_callback_t func) EXPORT_SYMBOL_GPL(call_rcu_bh); /* - * Queue an RCU callback for lazy invocation after a grace period. - * This will likely be later named something like "call_rcu_lazy()", - * but this change will require some way of tagging the lazy RCU - * callbacks in the list of pending callbacks. Until then, this - * function may only be called from __kfree_rcu(). - */ -void kfree_call_rcu(struct rcu_head *head, - rcu_callback_t func) -{ - __call_rcu(head, func, rcu_state_p, -1, 1); -} -EXPORT_SYMBOL_GPL(kfree_call_rcu); - -/* * Because a context switch is a grace period for RCU-sched and RCU-bh, * any blocking grace-period wait automatically implies a grace period * if there is only one CPU online at any point time during execution diff --git a/mm/slab_common.c b/mm/slab_common.c index 10f127b..2ea9866 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -1525,6 +1525,16 @@ void kzfree(const void *p) } EXPORT_SYMBOL(kzfree); +/* + * Queue Memory to be freed by RCU after a grace period. + */ +void kfree_call_rcu(struct rcu_head *head, + rcu_callback_t func) +{ + call_rcu_lazy(head, func); +} +EXPORT_SYMBOL_GPL(kfree_call_rcu); + /* Tracepoints definitions. */ EXPORT_TRACEPOINT_SYMBOL(kmalloc); EXPORT_TRACEPOINT_SYMBOL(kmem_cache_alloc); -- 2.7.4
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