tick/broadcast: Make idle check independent from mode and config
Currently the broadcast busy check, which prevents the idle code from
going into deep idle, works only in one shot mode.
If NOHZ and HIGHRES are off (config or command line) there is no
sanity check at all, so under certain conditions cpus are allowed to
go into deep idle, where the local timer stops, and are not woken up
again because there is no broadcast timer installed or a hrtimer based
broadcast device is not evaluated.
Move tick_broadcast_oneshot_control() into the common code and provide
proper subfunctions for the various config combinations.
The common check in tick_broadcast_oneshot_control() is for the C3STOP
misfeature flag of the local clock event device. If its not set, idle
can proceed. If set, further checks are necessary.
Provide checks for the trivial cases:
- If broadcast is disabled in the config, then return busy
- If oneshot mode (NOHZ/HIGHES) is disabled in the config, return
busy if the broadcast device is hrtimer based.
- If oneshot mode is enabled in the config call the original
tick_broadcast_oneshot_control() function. That function needs
extra checks which will be implemented in seperate patches.
[ Split out from a larger combo patch ]
Reported-and-tested-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Suzuki Poulose <Suzuki.Poulose@arm.com>
Cc: Lorenzo Pieralisi <Lorenzo.Pieralisi@arm.com>
Cc: Catalin Marinas <Catalin.Marinas@arm.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1507070929360.3916@nanos
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index 76446cb..55e13ef 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -343,6 +343,27 @@
tick_install_broadcast_device(newdev);
}
+/**
+ * tick_broadcast_oneshot_control - Enter/exit broadcast oneshot mode
+ * @state: The target state (enter/exit)
+ *
+ * The system enters/leaves a state, where affected devices might stop
+ * Returns 0 on success, -EBUSY if the cpu is used to broadcast wakeups.
+ *
+ * Called with interrupts disabled, so clockevents_lock is not
+ * required here because the local clock event device cannot go away
+ * under us.
+ */
+int tick_broadcast_oneshot_control(enum tick_broadcast_state state)
+{
+ struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
+
+ if (!(td->evtdev->features & CLOCK_EVT_FEAT_C3STOP))
+ return 0;
+
+ return __tick_broadcast_oneshot_control(state);
+}
+
#ifdef CONFIG_HOTPLUG_CPU
/*
* Transfer the do_timer job away from a dying cpu.