[PATCH 3.16 002/136] tick: broadcast-hrtimer: Remove overly clever return value abuse

[Ben Hutchings]

3.16.80-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

commit b8a62f1ff0ccb18fdc25c6150d1cd394610f4753 upstream.

The assignment of bc_moved in the conditional construct relies on the
fact that in the case of hrtimer_start() invocation the return value
is always 0. It took me a while to understand it.

We want to get rid of the hrtimer_start() return value. Open code the
logic which makes it readable as well.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Preeti U Murthy <preeti@xxxxxxxxxxxxxxxxxx>
Acked-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
Cc: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Link: http://lkml.kernel.org/r/20150414203503.404751457@xxxxxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
[bwh: Backported to 3.16 to ease backporting commit b9023b91dd02
 "tick: broadcast-hrtimer: Fix a race in bc_set_next"]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 kernel/time/tick-broadcast-hrtimer.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

--- a/kernel/time/tick-broadcast-hrtimer.c
+++ b/kernel/time/tick-broadcast-hrtimer.c
@@ -66,9 +66,11 @@ static int bc_set_next(ktime_t expires,
 	 * hrtimer_{start/cancel} functions call into tracing,
 	 * calls to these functions must be bound within RCU_NONIDLE.
 	 */
-	RCU_NONIDLE(bc_moved = (hrtimer_try_to_cancel(&bctimer) >= 0) ?
-		!hrtimer_start(&bctimer, expires, HRTIMER_MODE_ABS_PINNED) :
-			0);
+	RCU_NONIDLE({
+			bc_moved = hrtimer_try_to_cancel(&bctimer) >= 0;
+			if (bc_moved)
+				hrtimer_start(&bctimer, expires,
+					      HRTIMER_MODE_ABS_PINNED);});
 	if (bc_moved) {
 		/* Bind the "device" to the cpu */
 		bc->bound_on = smp_processor_id();