Messages in this thread Patch in this message | | | Date | Mon, 18 Sep 2006 16:28:06 -0400 (EDT) | From | Alan Stern <> | Subject | [PATCH 3/3] Don't call put methods while holding a spinlock |
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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>
---
Index: mm2/lib/klist.c =================================================================== --- mm2.orig/lib/klist.c +++ mm2/lib/klist.c @@ -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 klis 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 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 kl } i->i_cur = knode; spin_unlock(&i->i_klist->k_lock); + if (put && lnode) + put(lnode); return knode; } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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