From: Paul E. McKenney <paul.mckenney@linaro.org>
Date: Tue, 27 Mar 2012 23:02:08 +0000 (-0700)
Subject: rcu: Move PREEMPT_RCU preemption to switch_to() invocation
X-Git-Tag: v3.5-rc1~164^2^2^3~1
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=616c310e83b872024271c915c1b9ab505b9efad9;p=pandora-kernel.git

rcu: Move PREEMPT_RCU preemption to switch_to() invocation

Currently, PREEMPT_RCU readers are enqueued upon entry to the scheduler.
This is inefficient because enqueuing is required only if there is a
context switch, and entry to the scheduler does not guarantee a context
switch.

The commit therefore moves the enqueuing to immediately precede the
call to switch_to() from the scheduler.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Linus Torvalds <torvalds@linux-foundation.org>
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