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Commit 79447cdf authored by Prasad Sodagudi's avatar Prasad Sodagudi
Browse files

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: default avatarPrasad Sodagudi <psodagud@codeaurora.org>
parent bd8b86b1

kernel/time/hrtimer.c

+3 −0
Original line number Diff line number Diff line
@@ -52,6 +52,7 @@ 
#include <linux/timer.h>

#include <linux/freezer.h>

#include <linux/compat.h>

#include <linux/delay.h>



#include <linux/uaccess.h>
@@ -152,6 +153,7 @@ 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);

	}

}
@@ -1067,6 +1069,7 @@ 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);

kernel/time/tick-internal.h

+1 −0
Original line number Diff line number Diff line
@@ -164,3 +164,4 @@ DECLARE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases); 


extern u64 get_next_timer_interrupt(unsigned long basej, u64 basem);

void timer_clear_idle(void);

#define TIMER_LOCK_TIGHT_LOOP_DELAY_NS	350

kernel/time/timer.c

+2 −0
Original line number Diff line number Diff line
@@ -944,6 +944,7 @@ static struct timer_base *lock_timer_base(struct timer_list *timer, 
			raw_spin_unlock_irqrestore(&base->lock, *flags);

		}

		cpu_relax();

		ndelay(TIMER_LOCK_TIGHT_LOOP_DELAY_NS);

	}

}
@@ -1266,6 +1267,7 @@ 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);