linux-kernel - Re: [patch 1/3] new timerfd API

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Message-ID: <Pine.LNX.4.64.0709240838250.23830@alien.or.mcafeemobile.com>
Date:	Mon, 24 Sep 2007 08:42:47 -0700 (PDT)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Thomas Gleixner <tglx@...utronix.de>
cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Michael Kerrisk <mtk-manpages@....net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [patch 1/3] new timerfd API - new timerfd API

On Mon, 24 Sep 2007, Thomas Gleixner wrote:

> >  struct timerfd_ctx {
> >  	struct hrtimer tmr;
> > +	int clockid;
> >  	ktime_t tintv;
> >  	wait_queue_head_t wqh;
> >  	int expired;
> > +	u64 ticks;
> >  };
> 
> Can you please restructure the struct in a way which does not result in
> padding by the compiler ?
> 
> struct timerfd_ctx {
> 	struct hrtimer tmr;
> 	ktime_t tintv;
> 	wait_queue_head_t wqh;
> 	u64 ticks;
> 	int expired;
> 	int clockid;
> };

Sure.



> > +			ticks += (u64)
> >  				hrtimer_forward(&ctx->tmr,
> >  						hrtimer_cb_get_time(&ctx->tmr),
> 
> You need to use ctx->tmr.base->get_time() here, otherwise you might read
> a stale time value (in case that CONFIG_HIGH_RES_TIMERS is off).

Is the particular position of hrtimer_cb_get_time() in the code that would 
break here? Because function was added by your patch ;)
Did something change later?



> > +err_kfree_ctx:
> > +	kfree(ctx);
> > +	return error;
> 
> You really can avoid the goto here.

Ack.



- Davide


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