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

Ben Hutchings
2019-12-17T01:01:40Z

From: Thomas Gleixner <tglx@linutronix.de>

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@linutronix.de>
Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/20150414203503.404751457@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
[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@decadent.org.uk>
---
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();