diff options
Diffstat (limited to 'include/linux/rcupdate.h')
| -rw-r--r-- | include/linux/rcupdate.h | 33 |
1 files changed, 18 insertions, 15 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 48e5c03df1dd..23bcf71ffb06 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -1025,12 +1025,6 @@ static inline notrace void rcu_read_unlock_sched_notrace(void) #define RCU_POINTER_INITIALIZER(p, v) \ .p = RCU_INITIALIZER(v) -/* - * Does the specified offset indicate that the corresponding rcu_head - * structure can be handled by kvfree_rcu()? - */ -#define __is_kvfree_rcu_offset(offset) ((offset) < 4096) - /** * kfree_rcu() - kfree an object after a grace period. * @ptr: pointer to kfree for double-argument invocations. @@ -1041,11 +1035,11 @@ static inline notrace void rcu_read_unlock_sched_notrace(void) * 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. + * The kfree_rcu() function handles this issue. In order to have a universal + * callback function handling different offsets of rcu_head, the callback needs + * to determine the starting address of the freed object, which can be a large + * kmalloc or vmalloc allocation. To allow simply aligning the pointer down to + * page boundary for those, only offsets up to 4095 bytes can be accommodated. * If the offset is larger than 4095 bytes, a compile-time error will * be generated in kvfree_rcu_arg_2(). If this error is triggered, you can * either fall back to use of call_rcu() or rearrange the structure to @@ -1082,14 +1076,23 @@ static inline notrace void rcu_read_unlock_sched_notrace(void) #define kfree_rcu_mightsleep(ptr) kvfree_rcu_arg_1(ptr) #define kvfree_rcu_mightsleep(ptr) kvfree_rcu_arg_1(ptr) +/* + * In mm/slab_common.c, no suitable header to include here. + */ +void kvfree_call_rcu(struct rcu_head *head, void *ptr); + +/* + * The BUILD_BUG_ON() makes sure the rcu_head offset can be handled. See the + * comment of kfree_rcu() for details. + */ #define kvfree_rcu_arg_2(ptr, rhf) \ do { \ typeof (ptr) ___p = (ptr); \ \ - if (___p) { \ - BUILD_BUG_ON(!__is_kvfree_rcu_offset(offsetof(typeof(*(ptr)), rhf))); \ - kvfree_call_rcu(&((___p)->rhf), (void *) (___p)); \ - } \ + if (___p) { \ + BUILD_BUG_ON(offsetof(typeof(*(ptr)), rhf) >= 4096); \ + kvfree_call_rcu(&((___p)->rhf), (void *) (___p)); \ + } \ } while (0) #define kvfree_rcu_arg_1(ptr) \ |