From: Doug Chapman <dchapman@redhat.com>
Date: Thu, 6 Dec 2007 16:16:26 -0500
Subject: [cpufreq] don't take sem in cpufreq_quick_get
Message-id: 1196975786.1083.11.camel@athlon
O-Subject: [RHEL 5.2 PATCH 5/5] hang at 'Disabling ondemand cpu frequency scaling'
Bugzilla: 253416

Patch 5 of 5 for BZ 253416

backport of:

commit 9eb59573d4b86f347e6cd04f47a4c2082009fa58
Author: Andi Kleen <ak@suse.de>
Date:   Wed Oct 10 02:18:27 2007 +0200

    [CPUFREQ] Don't take semaphore in cpufreq_quick_get()

    I don't see any reason to take an expensive lock in cpufreq_quick_get()
    Reading policy->cur is a single atomic operation and after
    the lock is dropped again the state could change any time anyways.

    So don't take the lock in the first place.

    This also makes this function interrupt safe which is useful
    for some code of mine.

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 5ee1b94..b2356eb 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1024,12 +1024,7 @@ unsigned int cpufreq_quick_get(unsigned int cpu)
 	unsigned int ret = 0;
 
 	if (policy) {
-		if (unlikely(lock_policy_rwsem_read(cpu)))
-			return ret;
-
 		ret = policy->cur;
-
-		unlock_policy_rwsem_read(cpu);
 		cpufreq_cpu_put(policy);
 	}