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Commit 7e9f4b2d authored by Alan Stern's avatar Alan Stern Committed by Greg Kroah-Hartman
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Driver core: Don't call put methods while holding a spinlock 



The klist utility routines currently call _put methods while holding a
spinlock.  This is of course illegal; a put routine could try to
unregister a device and hence need to sleep.

No problems have arisen until now because in many cases klist removals
were done synchronously, so the _put methods were never actually used.
In other cases we may simply have been lucky.

This patch (as784) reworks the klist routines so that _put methods are
called only _after_ the klist's spinlock has been released.

Signed-off-by: default avatarAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 81107bf5

lib/klist.c

+15 −11
Original line number Diff line number Diff line
@@ -123,12 +123,10 @@ EXPORT_SYMBOL_GPL(klist_add_tail); 
static void klist_release(struct kref * kref)

{

	struct klist_node * n = container_of(kref, struct klist_node, n_ref);

	void (*put)(struct klist_node *) = n->n_klist->put;



	list_del(&n->n_node);

	complete(&n->n_removed);

	n->n_klist = NULL;

	if (put)

		put(n);

}



static int klist_dec_and_del(struct klist_node * n)
@@ -145,10 +143,14 @@ static int klist_dec_and_del(struct klist_node * n) 
void klist_del(struct klist_node * n)

{

	struct klist * k = n->n_klist;

	void (*put)(struct klist_node *) = k->put;



	spin_lock(&k->k_lock);

	klist_dec_and_del(n);

	if (!klist_dec_and_del(n))

		put = NULL;

	spin_unlock(&k->k_lock);

	if (put)

		put(n);

}



EXPORT_SYMBOL_GPL(klist_del);
@@ -161,10 +163,7 @@ EXPORT_SYMBOL_GPL(klist_del); 


void klist_remove(struct klist_node * n)

{

	struct klist * k = n->n_klist;

	spin_lock(&k->k_lock);

	klist_dec_and_del(n);

	spin_unlock(&k->k_lock);

	klist_del(n);

	wait_for_completion(&n->n_removed);

}
@@ -260,12 +259,15 @@ static struct klist_node * to_klist_node(struct list_head * n) 
struct klist_node * klist_next(struct klist_iter * i)

{

	struct list_head * next;

	struct klist_node * lnode = i->i_cur;

	struct klist_node * knode = NULL;

	void (*put)(struct klist_node *) = i->i_klist->put;



	spin_lock(&i->i_klist->k_lock);

	if (i->i_cur) {

		next = i->i_cur->n_node.next;

		klist_dec_and_del(i->i_cur);

	if (lnode) {

		next = lnode->n_node.next;

		if (!klist_dec_and_del(lnode))

			put = NULL;

	} else

		next = i->i_head->next;
@@ -275,6 +277,8 @@ struct klist_node * klist_next(struct klist_iter * i) 
	}

	i->i_cur = knode;

	spin_unlock(&i->i_klist->k_lock);

	if (put && lnode)

		put(lnode);

	return knode;

}