linux-kernel - [120/140] [CPUFREQ] revert "[CPUFREQ] remove rwsem lock from CPUFREQ_GOV

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Message-Id: <20100730173113.520470795@clark.site>
Date:	Fri, 30 Jul 2010 10:31:25 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Andrej Gelenberg <andrej.gelenberg@....edu>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Dave Jones <davej@...hat.com>
Subject: [120/140] [CPUFREQ] revert "[CPUFREQ] remove rwsem lock from CPUFREQ_GOV_STOP call (second call site)"

2.6.33-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Andrej Gelenberg <andrej.gelenberg@....edu>

commit accd846698439ba18250e8fd5681af280446b853 upstream.

395913d0b1db37092ea3d9d69b832183b1dd84c5 ("[CPUFREQ] remove rwsem lock
from CPUFREQ_GOV_STOP call (second call site)") is not needed, because
there is no rwsem lock in cpufreq_ondemand and cpufreq_conservative
anymore.  Lock should not be released until the work done.

Addresses https://bugzilla.kernel.org/show_bug.cgi?id=1594

Signed-off-by: Andrej Gelenberg <andrej.gelenberg@....edu>
Cc: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Cc: Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Signed-off-by: Dave Jones <davej@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 drivers/cpufreq/cpufreq.c |   11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1765,17 +1765,8 @@ static int __cpufreq_set_policy(struct c
 			dprintk("governor switch\n");
 
 			/* end old governor */
-			if (data->governor) {
-				/*
-				 * Need to release the rwsem around governor
-				 * stop due to lock dependency between
-				 * cancel_delayed_work_sync and the read lock
-				 * taken in the delayed work handler.
-				 */
-				unlock_policy_rwsem_write(data->cpu);
+			if (data->governor)
 				__cpufreq_governor(data, CPUFREQ_GOV_STOP);
-				lock_policy_rwsem_write(data->cpu);
-			}
 
 			/* start new governor */
 			data->governor = policy->governor;


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