linux-kernel - Re: [PATCH RFC tip/core/rcu 22/41] rcu: Simplify unboosting checks

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Date:	Wed, 1 Feb 2012 18:38:47 -0800
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@...ymtl.ca, niv@...ibm.com, tglx@...utronix.de,
	peterz@...radead.org, rostedt@...dmis.org, Valdis.Kletnieks@...edu,
	dhowells@...hat.com, eric.dumazet@...il.com, darren@...art.com,
	fweisbec@...il.com, patches@...aro.org,
	"Paul E. McKenney" <paul.mckenney@...aro.org>
Subject: Re: [PATCH RFC tip/core/rcu 22/41] rcu: Simplify unboosting checks

On Wed, Feb 01, 2012 at 11:41:40AM -0800, Paul E. McKenney wrote:
> From: "Paul E. McKenney" <paul.mckenney@...aro.org>
> 
> This is a port of commit #82e78d80 from TREE_PREEMPT_RCU to
> TINY_PREEMPT_RCU.
> 
> This commit uses the fact that current->rcu_boost_mutex is set
> any time that the RCU_READ_UNLOCK_BOOSTED flag is set in the
> current->rcu_read_unlock_special bitmask.  This allows tests of
> the bit to be changed to tests of the pointer, which in turn allows
> the RCU_READ_UNLOCK_BOOSTED flag to be eliminated.

Does this change affect rcu_read_unlock()'s logic to trigger the
slowpath only when special flags get set?

- Josh Triplett
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