linux-kernel - Re: [PATCH] RFC: abstract access to xtime

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Date:	Fri, 21 Jan 2011 21:23:49 +0800
From:	Yong Zhang <yong.zhang0@...il.com>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Torben Hohn <torbenh@....de>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...x.de>
Subject: Re: [PATCH] RFC: abstract access to xtime_lock into a set of
 inline functions

On Thu, Jan 20, 2011 at 12:30:29PM -0500, Christoph Hellwig wrote:
> On Thu, Jan 20, 2011 at 06:14:08PM +0100, Torben Hohn wrote:
> > the -rt patches change the xtime_lock to a raw_seqlock_t
> > so a pretty huge portion of the patch deals with changing
> > the locking functions.
> > 
> > this commit uses inline functions, to hide the type
> > of the lock.
> 
> That's not how kernel code usually works.
> 
> > -	write_seqlock(&xtime_lock);
> > +	xtime_write_seqlock();
> >  	do_timer(1);
> > -	write_sequnlock(&xtime_lock);
> > +	xtime_write_sequnlock();
> 
> However there's a pretty clear pattern of taking xtime_lock, calling
> do_timer and then releasing.  A useful thing you could do is to rename
> do_timer to do_timer_locked and make do_timer take and release
> xtime_lock in one place.

How about adding raw_seqlock just like what we have done for
spinlock? Thus xtime_lock can be defined to raw_seqlock and
others can also benefit from the raw_seqlock like xtime_lock.

Thanks,
Yong
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