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, 3 insertions, 0 deletions

diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 79fadcad21ff..6bd4247198e2 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -49,6 +49,7 @@
 #include <linux/sched/deadline.h>
 #include <linux/timer.h>
 #include <linux/freezer.h>
+#include <linux/delay.h>
 
 #include <asm/uaccess.h>
 
@@ -156,6 +157,7 @@ struct hrtimer_clock_base *lock_hrtimer_base(const struct hrtimer *timer,
 			raw_spin_unlock_irqrestore(&base->cpu_base->lock, *flags);
 		}
 		cpu_relax();
+		ndelay(TIMER_LOCK_TIGHT_LOOP_DELAY_NS);
 	}
 }
 
@@ -1061,6 +1063,7 @@ int hrtimer_cancel(struct hrtimer *timer)
 		if (ret >= 0)
 			return ret;
 		cpu_relax();
+		ndelay(TIMER_LOCK_TIGHT_LOOP_DELAY_NS);
 	}
 }
 EXPORT_SYMBOL_GPL(hrtimer_cancel);