[PATCH 18/19] timer: Add timer_curr_running()

[Frederic Weisbecker]

RCU needs to check if the current code is running a specific timer
callback, in the middle of other conditions to check the sanity of
RCU-nocb. Provide a helper for that.

Signed-off-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxx>
Cc: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: Lai Jiangshan <jiangshanlai@xxxxxxxxx>
Cc: Joel Fernandes <joel@xxxxxxxxxxxxxxxxx>
Cc: Neeraj Upadhyay <neeraju@xxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Boqun Feng <boqun.feng@xxxxxxxxx>
---
 include/linux/timer.h |  2 ++
 kernel/time/timer.c   | 13 +++++++++++++
 2 files changed, 15 insertions(+)

diff --git a/include/linux/timer.h b/include/linux/timer.h
index d10bc7e73b41..c75dbf7d118f 100644
--- a/include/linux/timer.h
+++ b/include/linux/timer.h
@@ -192,6 +192,8 @@ extern int try_to_del_timer_sync(struct timer_list *timer);
 
 #define del_singleshot_timer_sync(t) del_timer_sync(t)
 
+extern bool timer_curr_running(struct timer_list *timer);
+
 extern void init_timers(void);
 extern void run_local_timers(void);
 struct hrtimer;
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index de37e33a868d..9d41e4c4cfd4 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -1242,6 +1242,19 @@ int try_to_del_timer_sync(struct timer_list *timer)
 }
 EXPORT_SYMBOL(try_to_del_timer_sync);
 
+bool timer_curr_running(struct timer_list *timer)
+{
+	int i;
+
+	for (i = 0; i < NR_BASES; i++) {
+		struct timer_base *base = this_cpu_ptr(&timer_bases[i]);
+		if (base->running_timer == timer)
+			return true;
+	}
+
+	return false;
+}
+
 #ifdef CONFIG_PREEMPT_RT
 static __init void timer_base_init_expiry_lock(struct timer_base *base)
 {
-- 
2.25.1