From: Sebastian Ott <sebott@linux.vnet.ibm.com>
Date: Mon, 7 Sep 2015 17:52:06 +0000 (+0200)
Subject: s390/cio: improve locking during cmbe allocation
X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=616503d1d8940049841e5b6f2ab5157f37072ed9;p=openwrt%2Fstaging%2Fblogic.git

s390/cio: improve locking during cmbe allocation

During allocation of extended measurement blocks we check if the device is
already active for channel measurement and add the device to a list of
devices with active channel measurement. The check is done under ccwlock
protection and the list modification is guarded by a different lock.

To guarantee that both states are in sync make sure that both locks
are held during the allocation process (like it's already done for the
"normal" measurement block allocation).

Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Reviewed-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
---

diff --git a/drivers/s390/cio/cmf.c b/drivers/s390/cio/cmf.c
index 31677c075a8e..59b1ac24f992 100644
--- a/drivers/s390/cio/cmf.c
+++ b/drivers/s390/cio/cmf.c
@@ -821,42 +821,45 @@ static inline struct cmbe *cmbe_align(struct cmbe *c)
 
 static int alloc_cmbe(struct ccw_device *cdev)
 {
-	struct cmbe *cmbe;
 	struct cmb_data *cmb_data;
-	int ret;
+	struct cmbe *cmbe;
+	int ret = -ENOMEM;
 
 	cmbe = kzalloc (sizeof (*cmbe) * 2, GFP_KERNEL);
 	if (!cmbe)
-		return -ENOMEM;
+		return ret;
+
 	cmb_data = kzalloc(sizeof(struct cmb_data), GFP_KERNEL);
-	if (!cmb_data) {
-		ret = -ENOMEM;
+	if (!cmb_data)
 		goto out_free;
-	}
+
 	cmb_data->last_block = kzalloc(sizeof(struct cmbe), GFP_KERNEL);
-	if (!cmb_data->last_block) {
-		ret = -ENOMEM;
+	if (!cmb_data->last_block)
 		goto out_free;
-	}
+
 	cmb_data->size = sizeof(struct cmbe);
-	spin_lock_irq(cdev->ccwlock);
-	if (cdev->private->cmb) {
-		spin_unlock_irq(cdev->ccwlock);
-		ret = -EBUSY;
-		goto out_free;
-	}
 	cmb_data->hw_block = cmbe;
+
+	spin_lock(&cmb_area.lock);
+	spin_lock_irq(cdev->ccwlock);
+	if (cdev->private->cmb)
+		goto out_unlock;
+
 	cdev->private->cmb = cmb_data;
-	spin_unlock_irq(cdev->ccwlock);
 
 	/* activate global measurement if this is the first channel */
-	spin_lock(&cmb_area.lock);
 	if (list_empty(&cmb_area.list))
 		cmf_activate(NULL, 1);
 	list_add_tail(&cdev->private->cmb_list, &cmb_area.list);
-	spin_unlock(&cmb_area.lock);
 
+	spin_unlock_irq(cdev->ccwlock);
+	spin_unlock(&cmb_area.lock);
 	return 0;
+
+out_unlock:
+	spin_unlock_irq(cdev->ccwlock);
+	spin_unlock(&cmb_area.lock);
+	ret = -EBUSY;
 out_free:
 	if (cmb_data)
 		kfree(cmb_data->last_block);
@@ -869,19 +872,19 @@ static void free_cmbe(struct ccw_device *cdev)
 {
 	struct cmb_data *cmb_data;
 
+	spin_lock(&cmb_area.lock);
 	spin_lock_irq(cdev->ccwlock);
 	cmb_data = cdev->private->cmb;
 	cdev->private->cmb = NULL;
 	if (cmb_data)
 		kfree(cmb_data->last_block);
 	kfree(cmb_data);
-	spin_unlock_irq(cdev->ccwlock);
 
 	/* deactivate global measurement if this is the last channel */
-	spin_lock(&cmb_area.lock);
 	list_del_init(&cdev->private->cmb_list);
 	if (list_empty(&cmb_area.list))
 		cmf_activate(NULL, 0);
+	spin_unlock_irq(cdev->ccwlock);
 	spin_unlock(&cmb_area.lock);
 }