kernel: time: Add delay after cpu_relax() in tight loops

Tight loops of spin_lock_irqsave() and spin_unlock_irqrestore()
in timer and hrtimer are causing scheduling delays. Add delay of
few nano seconds after cpu_relax in the timer/hrtimer tight loops.

Change-Id: Iaa0ab92da93f7b245b1d922b6edca2bebdc0fbce
Signed-off-by: Prasad Sodagudi <psodagud@codeaurora.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 67646a316436..2d8b82d90c9f 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -798,6 +798,7 @@ static struct tvec_base *lock_timer_base(struct timer_list *timer,
 			spin_unlock_irqrestore(&base->lock, *flags);
 		}
 		cpu_relax();
+		ndelay(TIMER_LOCK_TIGHT_LOOP_DELAY_NS);
 	}
 }
 
@@ -1148,6 +1149,7 @@ int del_timer_sync(struct timer_list *timer)
 		if (ret >= 0)
 			return ret;
 		cpu_relax();
+		ndelay(TIMER_LOCK_TIGHT_LOOP_DELAY_NS);
 	}
 }
 EXPORT_SYMBOL(del_timer_sync);