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author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2016-01-08 18:43:50 +0300 |
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committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2016-02-24 06:59:55 +0300 |
commit | 9de630c4f264dec48e61edd871cb98b8e1b58250 (patch) | |
tree | e11bfe739aeb1e90d2a0fb31df4339bf39d2ced2 /include/linux/srcu.h | |
parent | 9fc9204ef9fdbe550fd81a554abce2b210e63e49 (diff) | |
download | linux-9de630c4f264dec48e61edd871cb98b8e1b58250.tar.xz |
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@canb.auug.org.au>
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Suggested-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'include/linux/srcu.h')
-rw-r--r-- | include/linux/srcu.h | 19 |
1 files changed, 17 insertions, 2 deletions
diff --git a/include/linux/srcu.h b/include/linux/srcu.h index f5f80c5643ac..dc8eb63c6568 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);\ |