Commit-ID: 9de630c4f264dec48e61edd871cb98b8e1b58250 Gitweb: http://git.kernel.org/tip/9de630c4f264dec48e61edd871cb98b8e1b58250 Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> AuthorDate: Fri, 8 Jan 2016 07:43:50 -0800 Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> CommitDate: Tue, 23 Feb 2016 19:59:55 -0800 rcu: Document unique-name limitation for DEFINE_STATIC_SRCU() SRCU uses per-CPU variables, and DEFINE_STATIC_SRCU() uses a static per-CPU variable. However, per-CPU variables have significant restrictions, for example, names of per-CPU variables must be globally unique, even if declared static. These restrictions carry over to DEFINE_STATIC_SRCU(), and this commit therefore documents these restrictions. Reported-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> Reported-by: kbuild test robot <fengguang.wu@xxxxxxxxx> Suggested-by: Boqun Feng <boqun.feng@xxxxxxxxx> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> Reviewed-by: Tejun Heo <tj@xxxxxxxxxx> --- include/linux/srcu.h | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) diff --git a/include/linux/srcu.h b/include/linux/srcu.h index f5f80c5..dc8eb63 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -99,8 +99,23 @@ void process_srcu(struct work_struct *work); } /* - * define and init a srcu struct at build time. - * dont't call init_srcu_struct() nor cleanup_srcu_struct() on it. + * Define and initialize a srcu struct at build time. + * Do -not- call init_srcu_struct() nor cleanup_srcu_struct() on it. + * + * Note that although DEFINE_STATIC_SRCU() hides the name from other + * files, the per-CPU variable rules nevertheless require that the + * chosen name be globally unique. These rules also prohibit use of + * DEFINE_STATIC_SRCU() within a function. If these rules are too + * restrictive, declare the srcu_struct manually. For example, in + * each file: + * + * static struct srcu_struct my_srcu; + * + * Then, before the first use of each my_srcu, manually initialize it: + * + * init_srcu_struct(&my_srcu); + * + * See include/linux/percpu-defs.h for the rules on per-CPU variables. */ #define __DEFINE_SRCU(name, is_static) \ static DEFINE_PER_CPU(struct srcu_struct_array, name##_srcu_array);\ -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
|