linux-kernel - Re: [v2 PATCH 1/4] timers: framework to identify pinned timers.

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Date:	Thu, 5 Mar 2009 17:53:40 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Arun R Bharadwaj <arun@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, linux-pm@...ts.linux-foundation.org,
	a.p.zijlstra@...llo.nl, ego@...ibm.com, tglx@...utronix.de,
	mingo@...e.hu, andi@...stfloor.org, venkatesh.pallipadi@...el.com,
	vatsa@...ux.vnet.ibm.com, arjan@...radead.org,
	svaidy@...ux.vnet.ibm.com
Subject: Re: [v2 PATCH 1/4] timers: framework to identify pinned timers.

On 03/04, Arun R Bharadwaj wrote:
>
> +static inline unsigned long tbase_get_flag_bits(struct timer_list *timer)
> +{
> +	return tbase_get_deferrable(timer->base) |
> +				tbase_get_pinned(timer->base);
> +}

I'd say this looks a bit strange. Hopefully compiler can optimize this code
to return (unsigned long)base & (TBASE_DEFERRABLE_FLAG | TBASE_PINNED_FLAG).

> @@ -736,6 +759,7 @@ void add_timer_on(struct timer_list *tim
>  	struct tvec_base *base = per_cpu(tvec_bases, cpu);
>  	unsigned long flags;
>
> +	timer_set_pinned(timer);

But we never clear TBASE_PINNED_FLAG?

If we use mod_timer() next time, the timer remains "pinned". I do not say
this is really wrong, but a bit strange imho.

Oleg.

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