From 87da149343c8c93f6984c0f4b9da7651709624f7 Mon Sep 17 00:00:00 2001 From: Greg Kroah-Hartman Date: Mon, 13 Jan 2014 14:43:11 -0800 Subject: Revert "kernfs: replace kernfs_node->u.completion with kernfs_root->deactivate_waitq" This reverts commit ea1c472dfeada211a0100daa7976e8e8e779b858. Tejun writes: I'm sorry but can you please revert the whole series? get_active() waiting while a node is deactivated has potential to lead to deadlock and that deactivate/reactivate interface is something fundamentally flawed and that cgroup will have to work with the remove_self() like everybody else. IOW, I think the first posting was correct. Cc: Tejun Heo Signed-off-by: Greg Kroah-Hartman --- fs/kernfs/dir.c | 27 ++++++++++++++++----------- 1 file changed, 16 insertions(+), 11 deletions(-) (limited to 'fs/kernfs') diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c index ed62de6..510b506 100644 --- a/fs/kernfs/dir.c +++ b/fs/kernfs/dir.c @@ -8,7 +8,6 @@ * This file is released under the GPLv2. */ -#include #include #include #include @@ -152,7 +151,6 @@ struct kernfs_node *kernfs_get_active(struct kernfs_node *kn) */ void kernfs_put_active(struct kernfs_node *kn) { - struct kernfs_root *root = kernfs_root(kn); int v; if (unlikely(!kn)) @@ -164,7 +162,11 @@ void kernfs_put_active(struct kernfs_node *kn) if (likely(v != KN_DEACTIVATED_BIAS)) return; - wake_up_all(&root->deactivate_waitq); + /* + * atomic_dec_return() is a mb(), we'll always see the updated + * kn->u.completion. + */ + complete(kn->u.completion); } /** @@ -175,22 +177,26 @@ void kernfs_put_active(struct kernfs_node *kn) */ static void kernfs_deactivate(struct kernfs_node *kn) { - struct kernfs_root *root = kernfs_root(kn); + DECLARE_COMPLETION_ONSTACK(wait); + int v; BUG_ON(!(kn->flags & KERNFS_REMOVED)); if (!(kernfs_type(kn) & KERNFS_ACTIVE_REF)) return; - rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_); + kn->u.completion = (void *)&wait; - atomic_add(KN_DEACTIVATED_BIAS, &kn->active); + rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_); + /* atomic_add_return() is a mb(), put_active() will always see + * the updated kn->u.completion. + */ + v = atomic_add_return(KN_DEACTIVATED_BIAS, &kn->active); - if (atomic_read(&kn->active) != KN_DEACTIVATED_BIAS) + if (v != KN_DEACTIVATED_BIAS) { lock_contended(&kn->dep_map, _RET_IP_); - - wait_event(root->deactivate_waitq, - atomic_read(&kn->active) == KN_DEACTIVATED_BIAS); + wait_for_completion(&wait); + } lock_acquired(&kn->dep_map, _RET_IP_); rwsem_release(&kn->dep_map, 1, _RET_IP_); @@ -607,7 +613,6 @@ struct kernfs_root *kernfs_create_root(struct kernfs_dir_ops *kdops, void *priv) root->dir_ops = kdops; root->kn = kn; - init_waitqueue_head(&root->deactivate_waitq); return root; } -- cgit v1.1