linux-kernel - Re: [PATCH 1/1] staging: hv: Optimize adj_guesttime function and add more detailed comments

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Date:	Mon, 10 May 2010 17:02:38 -0700
From:	Joe Perches <joe@...ches.com>
To:	Haiyang Zhang <haiyangz@...rosoft.com>
Cc:	"'linux-kernel@...r.kernel.org'" <linux-kernel@...r.kernel.org>,
	"'devel@...verdev.osuosl.org'" <devel@...verdev.osuosl.org>,
	"'virtualization@...ts.osdl.org'" <virtualization@...ts.osdl.org>,
	"'gregkh@...e.de'" <gregkh@...e.de>
Subject: Re: [PATCH 1/1] staging: hv: Optimize adj_guesttime function and
 add more detailed comments

On Mon, 2010-05-10 at 18:12 +0000, Haiyang Zhang wrote:
> diff --git a/drivers/staging/hv/hv_utils.c b/drivers/staging/hv/hv_utils.c
> index 8f1d3ba..c0f57a1 100644
> --- a/drivers/staging/hv/hv_utils.c
> +++ b/drivers/staging/hv/hv_utils.c
> @@ -106,28 +106,45 @@ static void shutdown_onchannelcallback(void *context)
>  		orderly_poweroff(false);
>  }
>  
> -
>  /*
> - * Synchronize time with host after reboot, restore, etc.
> + * Set guest time to host UTC time.
>   */
> -static void adj_guesttime(u64 hosttime, u8 flags)
> +static inline void do_adj_guesttime(u64 hosttime)
>  {
>  	s64 host_tns;
>  	struct timespec host_ts;
> -	static s32 scnt = 50;
>  
>  	host_tns = (hosttime - WLTIMEDELTA) * 100;
>  	host_ts = ns_to_timespec(host_tns);
>  
> +	do_settimeofday(&host_ts);
> +
> +	return;
> +}

Just a couple of style nits.

return at the end of a void function() is unnecessary.

> +
> +/*
> + * Synchronize time with host after reboot, restore, etc.
> + *
> + * ICTIMESYNCFLAG_SYNC flag bit indicates reboot, restore events of the VM.
> + * After reboot the flag ICTIMESYNCFLAG_SYNC is included in the first time
> + * message after the timesync channel is opened. Since the hv_utils module is
> + * loaded after hv_vmbus, the first message is usually missed. The other
> + * thing is, systime is automatically set to emulated hardware clock which may
> + * not be UTC time or in the same time zone. So, to override these effects, we
> + * use the first 50 time samples for initial system time setting.
> + */
> +static inline void adj_guesttime(u64 hosttime, u8 flags)
> +{
> +	static s32 scnt = 50;
> +
>  	if ((flags & ICTIMESYNCFLAG_SYNC) != 0) {
> -		do_settimeofday(&host_ts);
> +		do_adj_guesttime(hosttime);
>  		return;
>  	}
>  
> -	if ((flags & ICTIMESYNCFLAG_SAMPLE) != 0 &&
> -	    scnt > 0) {
> +	if ((flags & ICTIMESYNCFLAG_SAMPLE) != 0 && scnt > 0) {
>  		scnt--;
> -		do_settimeofday(&host_ts);
> +		do_adj_guesttime(hosttime);
>  	}
>  
>  	return;

here too


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