This commit creates a DEFINE_SRCU_FAST() that is similar to DEFINE_SRCU(),
but which creates an srcu_struct that is usable only by readers initiated
by srcu_read_lock_fast() and friends. Note that DEFINE_SRCU_FAST() is
usable only by built-in code, not from loadable modules.
Signed-off-by: Paul E. McKenney <paul...@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoy...@efficios.com>
Cc: Steven Rostedt <rost...@goodmis.org>
Cc: Sebastian Andrzej Siewior <bige...@linutronix.de>
Cc: <b...@vger.kernel.org>
---
include/linux/srcutiny.h | 1 +
include/linux/srcutree.h | 20 +++++++++++++++-----
2 files changed, 16 insertions(+), 5 deletions(-)
diff --git a/include/linux/srcutiny.h b/include/linux/srcutiny.h
index 51ce25f07930ee..00e5f05288d5e7 100644
--- a/include/linux/srcutiny.h
+++ b/include/linux/srcutiny.h
@@ -45,6 +45,7 @@ void srcu_drive_gp(struct work_struct *wp);
*/
#define DEFINE_SRCU(name) \
struct srcu_struct name = __SRCU_STRUCT_INIT(name, name, name)
+#define DEFINE_SRCU_FAST(name) DEFINE_SRCU(name)
#define DEFINE_STATIC_SRCU(name) \
static struct srcu_struct name = __SRCU_STRUCT_INIT(name, name, name)
diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
index 42098e0fa0b7dd..1adc58d2ab6425 100644
--- a/include/linux/srcutree.h
+++ b/include/linux/srcutree.h
@@ -189,23 +189,33 @@ struct srcu_struct {
* init_srcu_struct(&my_srcu);
*
* See include/linux/percpu-defs.h for the rules on per-CPU variables.
+ *
+ * DEFINE_SRCU_FAST() creates an srcu_struct and associated structures
+ * whose readers must be of the SRCU-fast variety. DEFINE_SRCU_FAST()
+ * cannot be used within modules due to there being no place to
+ * put the desired ->srcu_reader_flavor value. If in-module use of
+ * DEFINE_SRCU_FAST() becomes necessary, the srcu_struct structure will
+ * need to grow in order to store this value.
*/
#ifdef MODULE
-# define __DEFINE_SRCU(name, is_static)
\
+# define __DEFINE_SRCU(name, fast, is_static)
\
static struct srcu_usage name##_srcu_usage =
__SRCU_USAGE_INIT(name##_srcu_usage); \
is_static struct srcu_struct name = __SRCU_STRUCT_INIT_MODULE(name,
name##_srcu_usage); \
extern struct srcu_struct * const __srcu_struct_##name;
\
struct srcu_struct * const __srcu_struct_##name
\
__section("___srcu_struct_ptrs") = &name
#else
-# define __DEFINE_SRCU(name, is_static)
\
- static DEFINE_PER_CPU(struct srcu_data, name##_srcu_data);
\
+# define __DEFINE_SRCU(name, fast, is_static)
\
+ static DEFINE_PER_CPU(struct srcu_data, name##_srcu_data) = {
\
+ .srcu_reader_flavor = fast,
\
+ };
\
static struct srcu_usage name##_srcu_usage =
__SRCU_USAGE_INIT(name##_srcu_usage); \
is_static struct srcu_struct name =
\
__SRCU_STRUCT_INIT(name, name##_srcu_usage, name##_srcu_data)
+#define DEFINE_SRCU_FAST(name) __DEFINE_SRCU(name,
SRCU_READ_FLAVOR_FAST, /* not static */)
#endif
-#define DEFINE_SRCU(name) __DEFINE_SRCU(name, /* not static */)
-#define DEFINE_STATIC_SRCU(name) __DEFINE_SRCU(name, static)
+#define DEFINE_SRCU(name) __DEFINE_SRCU(name, 0, /* not static */)
+#define DEFINE_STATIC_SRCU(name) __DEFINE_SRCU(name, 0, static)
int __srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp);
void synchronize_srcu_expedited(struct srcu_struct *ssp);
--
2.40.1
