tick/broadcast: Check for hrtimer broadcast active early
authorThomas Gleixner <tglx@linutronix.de>
Tue, 7 Jul 2015 14:43:04 +0000 (16:43 +0200)
committerThomas Gleixner <tglx@linutronix.de>
Tue, 7 Jul 2015 16:46:48 +0000 (18:46 +0200)
If the current cpu is the one which has the hrtimer based broadcast
queued then we better return busy immediately instead of going through
loops and hoops to figure that out.

[ Split out from a larger combo patch ]

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
kernel/time/tick-broadcast.c

index 70b47bc..c8d731a 100644 (file)
@@ -706,6 +706,17 @@ int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
 
        if (state == TICK_BROADCAST_ENTER) {
                /*
+                * If the current CPU owns the hrtimer broadcast
+                * mechanism, it cannot go deep idle and we do not add
+                * the CPU to the broadcast mask. We don't have to go
+                * through the EXIT path as the local timer is not
+                * shutdown.
+                */
+               ret = broadcast_needs_cpu(bc, cpu);
+               if (ret)
+                       goto out;
+
+               /*
                 * If the broadcast device is in periodic mode, we
                 * return.
                 */
@@ -718,7 +729,10 @@ int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
 
                if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_oneshot_mask)) {
                        WARN_ON_ONCE(cpumask_test_cpu(cpu, tick_broadcast_pending_mask));
+
+                       /* Conditionally shut down the local timer. */
                        broadcast_shutdown_local(bc, dev);
+
                        /*
                         * We only reprogram the broadcast timer if we
                         * did not mark ourself in the force mask and
@@ -733,18 +747,20 @@ int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
                                ret = -EBUSY;
                        } else if (dev->next_event.tv64 < bc->next_event.tv64) {
                                tick_broadcast_set_event(bc, cpu, dev->next_event);
+                               /*
+                                * In case of hrtimer broadcasts the
+                                * programming might have moved the
+                                * timer to this cpu. If yes, remove
+                                * us from the broadcast mask and
+                                * return busy.
+                                */
+                               ret = broadcast_needs_cpu(bc, cpu);
+                               if (ret) {
+                                       cpumask_clear_cpu(cpu,
+                                               tick_broadcast_oneshot_mask);
+                               }
                        }
                }
-               /*
-                * If the current CPU owns the hrtimer broadcast
-                * mechanism, it cannot go deep idle and we remove the
-                * CPU from the broadcast mask. We don't have to go
-                * through the EXIT path as the local timer is not
-                * shutdown.
-                */
-               ret = broadcast_needs_cpu(bc, cpu);
-               if (ret)
-                       cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
        } else {
                if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_oneshot_mask)) {
                        clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);