linux-kernel - Re: [PATCHv2 4/6] pps: add kernel consumer support

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Date:	Mon, 1 Mar 2010 13:48:01 +0300
From:	Alexander Gordeev <lasaine@....cs.msu.su>
To:	Rodolfo Giometti <giometti@...eenne.com>
Cc:	linux-kernel@...r.kernel.org, linuxpps@...enneenne.com,
	"Nikita V. Youshchenko" <yoush@...msu.su>, stas@....cs.msu.su,
	john stultz <johnstul@...ibm.com>,
	Randy Dunlap <rdunlap@...otime.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mauro Carvalho Chehab <mchehab@...hat.com>,
	Ryusuke Konishi <konishi.ryusuke@....ntt.co.jp>,
	Avi Kivity <avi@...hat.com>, Reg Clemens <clemens@....com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Dave Jones <davej@...hat.com>, linux-doc@...r.kernel.org
Subject: Re: [PATCHv2 4/6] pps: add kernel consumer support

On Mon, 1 Mar 2010 09:29:16 +0100
Rodolfo Giometti <giometti@...eenne.com> wrote:

> On Wed, Feb 24, 2010 at 03:28:15PM +0300, Alexander Gordeev wrote:
> > Add an optional feature of PPSAPI, kernel consumer support, which uses
> > the added hardpps() function.
> > 
> > Signed-off-by: Alexander Gordeev <lasaine@....cs.msu.su>
> 
> Acked-by: Rodolfo Giometti <giometti@...ux.it>
> 
> However see the note below.
> 
> > ---
> >  Documentation/ioctl/ioctl-number.txt |    2 +-
> >  drivers/pps/kapi.c                   |   26 +++++++++++++
> >  drivers/pps/pps.c                    |   67 +++++++++++++++++++++++++++++++++-
> >  include/linux/pps.h                  |    7 ++++
> >  include/linux/pps_kernel.h           |    6 +++
> >  5 files changed, 106 insertions(+), 2 deletions(-)
> > 
> > diff --git a/Documentation/ioctl/ioctl-number.txt b/Documentation/ioctl/ioctl-number.txt
> > index 9473749..d68718b 100644
> > --- a/Documentation/ioctl/ioctl-number.txt
> > +++ b/Documentation/ioctl/ioctl-number.txt
> > @@ -152,7 +152,7 @@ Code	Seq#	Include File		Comments
> >  'p'	40-7F	linux/nvram.h
> >  'p'	80-9F				user-space parport
> >  					<mailto:tim@...erelk.net>
> > -'p'	a1-a4	linux/pps.h		LinuxPPS
> > +'p'	a1-a5	linux/pps.h		LinuxPPS
> >  					<mailto:giometti@...ux.it>
> >  'q'	00-1F	linux/serio.h
> >  'q'	80-FF				Internet PhoneJACK, Internet LineJACK
> > diff --git a/drivers/pps/kapi.c b/drivers/pps/kapi.c
> > index b87f699..5871744 100644
> > --- a/drivers/pps/kapi.c
> > +++ b/drivers/pps/kapi.c
> > @@ -25,6 +25,7 @@
> >  #include <linux/init.h>
> >  #include <linux/sched.h>
> >  #include <linux/time.h>
> > +#include <linux/timex.h>
> >  #include <linux/spinlock.h>
> >  #include <linux/idr.h>
> >  #include <linux/fs.h>
> > @@ -37,6 +38,12 @@
> >  DEFINE_SPINLOCK(pps_idr_lock);
> >  DEFINE_IDR(pps_idr);
> >  
> > +/* state variables to bind kernel consumer */
> > +/* PPS API (RFC 2783): current source and mode for ``kernel consumer'' */
> > +DEFINE_SPINLOCK(pps_kc_hardpps_lock);
> > +void	*pps_kc_hardpps_dev;	/* some unique pointer to device */
> > +int	pps_kc_hardpps_mode;	/* mode bits for kernel consumer */
> > +
> >  /*
> >   * Local functions
> >   */
> > @@ -248,6 +255,15 @@ void pps_unregister_source(int source)
> >  	}
> >  	spin_unlock_irq(&pps_idr_lock);
> >  
> > +	spin_lock_irq(&pps_kc_hardpps_lock);
> > +	if (pps == pps_kc_hardpps_dev) {
> > +		pps_kc_hardpps_mode = 0;
> > +		pps_kc_hardpps_dev = NULL;
> > +		spin_unlock_irq(&pps_kc_hardpps_lock);
> > +		pr_info("unbound kernel consumer on device removal\n");
> > +	} else
> > +		spin_unlock_irq(&pps_kc_hardpps_lock);
> > +
> 
> I suppose you are using such if-else schema due the fact pr_info is
> too slow to be executed with helded spinlock, arent't you? :)

Yes, indeed. Is it ok? :)

-- 
  Alexander

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