Change rcu_sync_enter() to return "need_sync" to let the caller
know whether we did the FAST -> SLOW transition or not.
This is particularly useful in exclusive mode, for example
percpu_down_write() can avoid clear_fast_ctr() if rcu_sync_enter()
returns F.
Signed-off-by: Oleg Nesterov <o...@redhat.com>
---
include/linux/rcusync.h | 2 +-
kernel/rcusync.c | 4 +++-
2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/include/linux/rcusync.h b/include/linux/rcusync.h
index 5689f24..6f4c75b 100644
--- a/include/linux/rcusync.h
+++ b/include/linux/rcusync.h
@@ -37,7 +37,7 @@ enum rcu_sync_type { RCU_SYNC, RCU_SCHED_SYNC, RCU_BH_SYNC };
extern void rcu_sync_init(struct rcu_sync_struct *,
enum rcu_sync_type, bool excl);
-extern void rcu_sync_enter(struct rcu_sync_struct *);
+extern bool rcu_sync_enter(struct rcu_sync_struct *);
extern void rcu_sync_exit(struct rcu_sync_struct *);
extern void rcu_sync_dtor(struct rcu_sync_struct *);
diff --git a/kernel/rcusync.c b/kernel/rcusync.c
index 667eb7d..d03d8e5 100644
--- a/kernel/rcusync.c
+++ b/kernel/rcusync.c
@@ -42,7 +42,7 @@ void rcu_sync_init(struct rcu_sync_struct *rss,
rss->exclusive = excl;
}
-void rcu_sync_enter(struct rcu_sync_struct *rss)
+bool rcu_sync_enter(struct rcu_sync_struct *rss)
{
bool need_wait, need_sync;
@@ -73,6 +73,8 @@ void rcu_sync_enter(struct rcu_sync_struct *rss)
*/
BUG_ON(rss->gp_state != GP_PASSED);
}
+
+ return need_sync;
}
static void rcu_sync_func(struct rcu_head *rcu)
--
1.5.5.1
--
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