linux-kernel - [PATCH 1/2] pm_qos: remove the BKL

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Message-ID: <20090813140716.4490ab37@bike.lwn.net>
Date:	Thu, 13 Aug 2009 14:07:16 -0600
From:	Jonathan Corbet <corbet@....net>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Ingo Molnar <mingo@...e.hu>, Mark Gross <mgross@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: [PATCH 1/2] pm_qos: remove the BKL

pm_qos_power_open got its lock_kernel() calls from the open() pushdown.  A
look at the code shows that the only global resources accessed are
pm_qos_array and "name".  pm_qos_array doesn't change (things pointed to
therein do change, but they are atomics and/or are protected by
pm_qos_lock).  Accesses to "name" are totally unprotected with or without
the BKL; that will be fixed shortly.  The BKL is not helpful here; take it
out.

Signed-off-by: Jonathan Corbet <corbet@....net>
Cc: Mark Gross <mgross@...ux.intel.com>
---
 kernel/pm_qos_params.c |    8 +-------
 1 files changed, 1 insertions(+), 7 deletions(-)

diff --git a/kernel/pm_qos_params.c b/kernel/pm_qos_params.c
index dfdec52..d96b83e 100644
--- a/kernel/pm_qos_params.c
+++ b/kernel/pm_qos_params.c
@@ -29,7 +29,6 @@
 
 #include <linux/pm_qos_params.h>
 #include <linux/sched.h>
-#include <linux/smp_lock.h>
 #include <linux/spinlock.h>
 #include <linux/slab.h>
 #include <linux/time.h>
@@ -352,20 +351,15 @@ static int pm_qos_power_open(struct inode *inode, struct file *filp)
 	int ret;
 	long pm_qos_class;
 
-	lock_kernel();
 	pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
 	if (pm_qos_class >= 0) {
 		filp->private_data = (void *)pm_qos_class;
 		sprintf(name, "process_%d", current->pid);
 		ret = pm_qos_add_requirement(pm_qos_class, name,
 					PM_QOS_DEFAULT_VALUE);
-		if (ret >= 0) {
-			unlock_kernel();
+		if (ret >= 0)
 			return 0;
-		}
 	}
-	unlock_kernel();
-
 	return -EPERM;
 }
 
-- 
1.6.2.5

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