tick/broadcast: Allow late registered device to enter oneshot mode

The broadcast device is switched to oneshot mode when the system switches
to oneshot mode. If a broadcast clock event device is registered after the
system switched to oneshot mode, it will stay in periodic mode forever.

Ensure that a late registered device which is selected as broadcast device
is initialized in oneshot mode when the system already uses oneshot mode.

[ tglx: Massage changelog ]

Signed-off-by: Jindong Yue <jindong.yue@nxp.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210331083318.21794-1-jindong.yue@nxp.com

diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index 6ec7855..a440552 100644 (file)
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -107,6 +107,19 @@ void tick_install_broadcast_device(struct clock_event_device *dev)
        tick_broadcast_device.evtdev = dev;
        if (!cpumask_empty(tick_broadcast_mask))
                tick_broadcast_start_periodic(dev);
+
+       if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
+               return;
+
+       /*
+        * If the system already runs in oneshot mode, switch the newly
+        * registered broadcast device to oneshot mode explicitly.
+        */
+       if (tick_broadcast_oneshot_active()) {
+               tick_broadcast_switch_to_oneshot();
+               return;
+       }
+
        /*
         * Inform all cpus about this. We might be in a situation
         * where we did not switch to oneshot mode because the per cpu
@@ -115,8 +128,7 @@ void tick_install_broadcast_device(struct clock_event_device *dev)
         * notification the systems stays stuck in periodic mode
         * forever.
         */
-       if (dev->features & CLOCK_EVT_FEAT_ONESHOT)
-               tick_clock_notify();
+       tick_clock_notify();
 }
 
 /*