percpu_ref: remove unnecessary RCU grace period for staggered atomic switching confir...

[cascardo/linux.git] / lib / percpu-refcount.c

diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c
index 27fe749..8ade009 100644 (file)
--- a/lib/percpu-refcount.c
+++ b/lib/percpu-refcount.c
@@ -177,17 +177,11 @@ static void __percpu_ref_switch_to_atomic(struct percpu_ref *ref,
                call_rcu_sched(&ref->rcu, percpu_ref_switch_to_atomic_rcu);
        } else if (confirm_switch) {
                /*
-                * Somebody already set ATOMIC.  Switching may still be in
-                * progress.  @confirm_switch must be invoked after the
-                * switching is complete and a full sched RCU grace period
-                * has passed.  Wait synchronously for the previous
-                * switching and schedule @confirm_switch invocation.
+                * Somebody else already set ATOMIC.  Wait for its
+                * completion and invoke @confirm_switch() directly.
                 */
                wait_event(percpu_ref_switch_waitq, !ref->confirm_switch);
-               ref->confirm_switch = confirm_switch;
-
-               percpu_ref_get(ref);    /* put after confirmation */
-               call_rcu_sched(&ref->rcu, percpu_ref_call_confirm_rcu);
+               confirm_switch(ref);
        }
 }
 
@@ -211,10 +205,6 @@ static void __percpu_ref_switch_to_atomic(struct percpu_ref *ref,
  * but it may block if @confirm_kill is specified and @ref is already in
  * the process of switching to atomic mode.  In such cases, @confirm_switch
  * will be invoked after the switching is complete.
- *
- * Due to the way percpu_ref is implemented, @confirm_switch will be called
- * after at least one full sched RCU grace period has passed but this is an
- * implementation detail and must not be depended upon.
  */
 void percpu_ref_switch_to_atomic(struct percpu_ref *ref,
                                 percpu_ref_func_t *confirm_switch)
@@ -290,11 +280,7 @@ void percpu_ref_switch_to_percpu(struct percpu_ref *ref)
  *
  * This function normally doesn't block and can be called from any context
  * but it may block if @confirm_kill is specified and @ref is in the
- * process of switching to atomic mode by percpu_ref_switch_atomic().
- *
- * Due to the way percpu_ref is implemented, @confirm_switch will be called
- * after at least one full sched RCU grace period has passed but this is an
- * implementation detail and must not be depended upon.
+ * process of switching to atomic mode by percpu_ref_switch_to_atomic().
  */
 void percpu_ref_kill_and_confirm(struct percpu_ref *ref,
                                 percpu_ref_func_t *confirm_kill)