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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: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Alan Stern 2006-09-18 16:28:06 -04:00 committed by Greg Kroah-Hartman
parent 81107bf531
commit 7e9f4b2d3e
1 changed files with 15 additions and 11 deletions
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26
lib/klist.c
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@ -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;
}