linux-kernel - Re: [tip:timers/urgent] tick: Fix oneshot broadcast setup really

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Date:	Thu, 19 Apr 2012 10:29:46 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
cc:	Santosh Shilimkar <santosh.shilimkar@...com>, mingo@...nel.org,
	hpa@...or.com, linux-kernel@...r.kernel.org,
	torvalds@...ux-foundation.org, svenjoac@....de, rjw@...k.pl,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:timers/urgent] tick: Fix oneshot broadcast setup really

On Wed, 18 Apr 2012, Suresh Siddha wrote:
> On Wed, 2012-04-18 at 17:31 +0200, Thomas Gleixner wrote:
> From: Suresh Siddha <suresh.b.siddha@...el.com>
> Subject: tick: Fix the spurious broadcast timer ticks
> 
> During resume, tick_resume_broadcast() programs the broadcast timer
> in oneshot mode unconditionally. On the platforms where broadcast timer
> is not really required, this will generate spurious broadcast timer ticks
> upon resume. For example, on the always running apic timer platforms with
> HPET, I see spurious hpet tick once every ~5minutes (which is the 32-bit
> hpet counter wraparound time).
> 
> Similar to boot time, during resume make the oneshot mode setting of
> the broadcast clock event device conditional on the state of active broadcast
> users. 
> 
> Signed-off-by: Suresh Siddha <suresh.b.siddha@...el.com>

Sven, Santosh, can you confirm that this works for you on top of the
other two patches?

> ---
>  kernel/time/tick-broadcast.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
> index bf57abd..766cd82 100644
> --- a/kernel/time/tick-broadcast.c
> +++ b/kernel/time/tick-broadcast.c
> @@ -346,7 +346,8 @@ int tick_resume_broadcast(void)
>  						     tick_get_broadcast_mask());
>  			break;
>  		case TICKDEV_MODE_ONESHOT:
> -			broadcast = tick_resume_broadcast_oneshot(bc);
> +			if (!cpumask_empty(tick_get_broadcast_mask()))
> +				broadcast = tick_resume_broadcast_oneshot(bc);
>  			break;
>  		}
>  	}
> 
> 
> 
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