clockevents: Warn if cpu_all_mask is used as cpumask

Using cpu_all_mask in clockevents cpumask may result in issues while
comparing multiple clockevent devices to choose the preferred one.

On one of the platforms with 2 system (i.e. non per-CPU) timers with
different ratings, having cpu_all_mask for one of the device resulted in a
boot hang due to a endless loop in clockevents_notify_released() as both
were clocksources were selected as preferred.

In order to prevent such issues in the future, warn if any clockevent
driver sets cpu_all_mask as it's cpumask and just override it to use
cpu_possible_mask. All the existing occurrences of cpu_all_mask are already
replaced with cpu_possible_mask.

Signed-off-by: Sudeep Holla <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]

diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index 16c027e9cc730a38d1bb97da89dd9f30c4557145..8c0e4092f661824edf50a85342284d9ddcb03e6b 100644 (file)
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -463,6 +463,12 @@ void clockevents_register_device(struct clock_event_device *dev)
                dev->cpumask = cpumask_of(smp_processor_id());
        }
 
+       if (dev->cpumask == cpu_all_mask) {
+               WARN(1, "%s cpumask == cpu_all_mask, using cpu_possible_mask instead\n",
+                    dev->name);
+               dev->cpumask = cpu_possible_mask;
+       }
+
        raw_spin_lock_irqsave(&clockevents_lock, flags);
 
        list_add(&dev->list, &clockevent_devices);