linux-kernel - Re: [PATCH tip/core/rcu 0/8] RCU callback-numbering simplifications for 3.11

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Date:	Sat, 13 Apr 2013 11:37:45 -0700
From:	Josh Triplett <josh@...htriplett.org>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, laijs@...fujitsu.com,
	dipankar@...ibm.com, akpm@...ux-foundation.org,
	mathieu.desnoyers@...icios.com, niv@...ibm.com, tglx@...utronix.de,
	peterz@...radead.org, rostedt@...dmis.org, Valdis.Kletnieks@...edu,
	dhowells@...hat.com, edumazet@...gle.com, darren@...art.com,
	fweisbec@...il.com, sbw@....edu
Subject: Re: [PATCH tip/core/rcu 0/8] RCU callback-numbering simplifications
 for 3.11

On Fri, Apr 12, 2013 at 04:32:11PM -0700, Paul E. McKenney wrote:
> This series takes advantage of callback numbering to simplify RCU's
> grace-period machinery, in some cases also reducing the number of
> lock acquisitions (though the resulting change in performance is not
> perceptible).  The individual patches are as follows:
> 
> 1.	Move code to make way for the code-combining in later patches.
> 	This commit makes no changes, just moves code.
> 
> 2.	Make __note_new_gpnum() also check for the ends of prior grace
> 	periods, thus eliminating the earlier possibility of a given
> 	CPU becoming aware of the start of the next grace period before
> 	becoming aware of the end of the previous grace period.  Yes,
> 	the code did handle this correctly, but now it doesn't need to.
> 	More important, now I don't need to think about how it handles
> 	this correctly.
> 
> 3.	Rename note_new_gpnum() to note_gp_changes() in preparation for
> 	later merge of rcu_process_gp_end() into this function.
> 
> 4.	Change calls to rcu_process_gp_end() to instead call
> 	note_gp_changes(), and also remove the now-used rcu_process_gp_end().
> 
> 5.	Remove duplicate code by merging __rcu_process_gp_end() into
> 	__note_gp_changes().
> 
> 6.	Eliminate now-redundant call to check_for_new_grace_period().  This
> 	leaves only a single caller, so inline check_for_new_grace_period().
> 
> 7.	Given that rcu_start_gp_per_cpu() is a trivial wrapper function
> 	with only one caller, inline it into its sole remaining call site.
> 
> 8.	Eliminate now-redundant call to note_gp_changes().

For all 8:
Reviewed-by: Josh Triplett <josh@...htriplett.org>
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