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Commit ffa423fb authored by WANG Cong's avatar WANG Cong Committed by David S. Miller
Browse files

tap: convert a mutex to a spinlock 



We are not allowed to block on the RCU reader side, so can't
just hold the mutex as before. As a quick fix, convert it to
a spinlock.

Fixes: d9f1f61c ("tap: Extending tap device create/destroy APIs")
Reported-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Tested-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Cc: Sainath Grandhi <sainath.grandhi@intel.com>
Signed-off-by: default avatarCong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 6a146f3a

drivers/net/tap.c

+9 −9
Original line number Diff line number Diff line
@@ -106,7 +106,7 @@ struct major_info { 
	struct rcu_head rcu;

	dev_t major;

	struct idr minor_idr;

	struct mutex minor_lock;

	spinlock_t minor_lock;

	const char *device_name;

	struct list_head next;

};
@@ -416,15 +416,15 @@ int tap_get_minor(dev_t major, struct tap_dev *tap) 
		goto unlock;

	}



	mutex_lock(&tap_major->minor_lock);

	retval = idr_alloc(&tap_major->minor_idr, tap, 1, TAP_NUM_DEVS, GFP_KERNEL);

	spin_lock(&tap_major->minor_lock);

	retval = idr_alloc(&tap_major->minor_idr, tap, 1, TAP_NUM_DEVS, GFP_ATOMIC);

	if (retval >= 0) {

		tap->minor = retval;

	} else if (retval == -ENOSPC) {

		netdev_err(tap->dev, "Too many tap devices\n");

		retval = -EINVAL;

	}

	mutex_unlock(&tap_major->minor_lock);

	spin_unlock(&tap_major->minor_lock);



unlock:

	rcu_read_unlock();
@@ -442,12 +442,12 @@ void tap_free_minor(dev_t major, struct tap_dev *tap) 
		goto unlock;

	}



	mutex_lock(&tap_major->minor_lock);

	spin_lock(&tap_major->minor_lock);

	if (tap->minor) {

		idr_remove(&tap_major->minor_idr, tap->minor);

		tap->minor = 0;

	}

	mutex_unlock(&tap_major->minor_lock);

	spin_unlock(&tap_major->minor_lock);



unlock:

	rcu_read_unlock();
@@ -467,13 +467,13 @@ static struct tap_dev *dev_get_by_tap_file(int major, int minor) 
		goto unlock;

	}



	mutex_lock(&tap_major->minor_lock);

	spin_lock(&tap_major->minor_lock);

	tap = idr_find(&tap_major->minor_idr, minor);

	if (tap) {

		dev = tap->dev;

		dev_hold(dev);

	}

	mutex_unlock(&tap_major->minor_lock);

	spin_unlock(&tap_major->minor_lock);



unlock:

	rcu_read_unlock();
@@ -1244,7 +1244,7 @@ static int tap_list_add(dev_t major, const char *device_name) 
	tap_major->major = MAJOR(major);



	idr_init(&tap_major->minor_idr);

	mutex_init(&tap_major->minor_lock);

	spin_lock_init(&tap_major->minor_lock);



	tap_major->device_name = device_name;