diff options
author | André Fabian Silva Delgado <emulatorman@parabola.nu> | 2016-01-20 14:01:31 -0300 |
---|---|---|
committer | André Fabian Silva Delgado <emulatorman@parabola.nu> | 2016-01-20 14:01:31 -0300 |
commit | b4b7ff4b08e691656c9d77c758fc355833128ac0 (patch) | |
tree | 82fcb00e6b918026dc9f2d1f05ed8eee83874cc0 /include/linux/types.h | |
parent | 35acfa0fc609f2a2cd95cef4a6a9c3a5c38f1778 (diff) |
Linux-libre 4.4-gnupck-4.4-gnu
Diffstat (limited to 'include/linux/types.h')
-rw-r--r-- | include/linux/types.h | 18 |
1 files changed, 16 insertions, 2 deletions
diff --git a/include/linux/types.h b/include/linux/types.h index c314989d9..70dd3dfde 100644 --- a/include/linux/types.h +++ b/include/linux/types.h @@ -35,7 +35,7 @@ typedef __kernel_gid16_t gid16_t; typedef unsigned long uintptr_t; -#ifdef CONFIG_UID16 +#ifdef CONFIG_HAVE_UID16 /* This is defined by include/asm-{arch}/posix_types.h */ typedef __kernel_old_uid_t old_uid_t; typedef __kernel_old_gid_t old_gid_t; @@ -205,11 +205,25 @@ struct ustat { * struct callback_head - callback structure for use with RCU and task_work * @next: next update requests in a list * @func: actual update function to call after the grace period. + * + * The struct is aligned to size of pointer. On most architectures it happens + * naturally due ABI requirements, but some architectures (like CRIS) have + * weird ABI and we need to ask it explicitly. + * + * The alignment is required to guarantee that bits 0 and 1 of @next will be + * clear under normal conditions -- as long as we use call_rcu(), + * call_rcu_bh(), call_rcu_sched(), or call_srcu() to queue callback. + * + * This guarantee is important for few reasons: + * - future call_rcu_lazy() will make use of lower bits in the pointer; + * - the structure shares storage spacer in struct page with @compound_head, + * which encode PageTail() in bit 0. The guarantee is needed to avoid + * false-positive PageTail(). */ struct callback_head { struct callback_head *next; void (*func)(struct callback_head *head); -}; +} __attribute__((aligned(sizeof(void *)))); #define rcu_head callback_head typedef void (*rcu_callback_t)(struct rcu_head *head); |