From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Date: Tue, 26 Oct 2010 09:11:40 +0000 (-0700)
Subject: rcu: Make synchronize_srcu_expedited() fast if running readers
X-Git-Tag: v2.6.38-rc1~492^2^2~8
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=46fdb0937f26124700fc9fc80da4776330cc00d3;p=pandora-kernel.git

rcu: Make synchronize_srcu_expedited() fast if running readers

The synchronize_srcu_expedited() function is currently quick if there
are no active readers, but will delay a full jiffy if there are any.
If these readers leave their SRCU read-side critical sections quickly,
this is way too long to wait.  So this commit first waits ten microseconds,
and only then falls back to jiffy-at-a-time waiting.

Reported-by: Avi Kivity <avi@redhat.com>
Reported-by: Marcelo Tosatti <mtosatti@redhat.com>
Tested-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---

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