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Revert "kernfs: remove KERNFS_ACTIVE_REF and add kernfs_lockdep()"

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This reverts commit a69d001cfc.

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 <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Greg Kroah-Hartman 2014-01-13 14:39:52 -08:00
parent 798c75a0d4
commit 0890147fe0
2 changed files with 12 additions and 20 deletions
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31
fs/kernfs/dir.c
View file

@ -22,15 +22,6 @@ DEFINE_MUTEX(kernfs_mutex);
#define rb_to_kn(X) rb_entry((X), struct kernfs_node, rb)
static bool kernfs_lockdep(struct kernfs_node *kn)
{
#ifdef CONFIG_DEBUG_LOCK_ALLOC
return kn->flags & KERNFS_LOCKDEP;
#else
return false;
#endif
}
/**
* kernfs_name_hash
* @name: Null terminated string to hash
@ -147,7 +138,7 @@ struct kernfs_node *kernfs_get_active(struct kernfs_node *kn)
if (!atomic_inc_unless_negative(&kn->active))
return NULL;
if (kernfs_lockdep(kn))
if (kn->flags & KERNFS_LOCKDEP)
rwsem_acquire_read(&kn->dep_map, 0, 1, _RET_IP_);
return kn;
}
@ -167,7 +158,7 @@ void kernfs_put_active(struct kernfs_node *kn)
if (unlikely(!kn))
return;
if (kernfs_lockdep(kn))
if (kn->flags & KERNFS_LOCKDEP)
rwsem_release(&kn->dep_map, 1, _RET_IP_);
v = atomic_dec_return(&kn->active);
if (likely(v != KN_DEACTIVATED_BIAS))
@ -188,21 +179,21 @@ static void kernfs_deactivate(struct kernfs_node *kn)
BUG_ON(!(kn->flags & KERNFS_REMOVED));
if (!(kernfs_type(kn) & KERNFS_ACTIVE_REF))
return;
rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_);
atomic_add(KN_DEACTIVATED_BIAS, &kn->active);
if (kernfs_lockdep(kn)) {
rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_);
if (atomic_read(&kn->active) != KN_DEACTIVATED_BIAS)
lock_contended(&kn->dep_map, _RET_IP_);
}
if (atomic_read(&kn->active) != KN_DEACTIVATED_BIAS)
lock_contended(&kn->dep_map, _RET_IP_);
wait_event(root->deactivate_waitq,
atomic_read(&kn->active) == KN_DEACTIVATED_BIAS);
if (kernfs_lockdep(kn)) {
lock_acquired(&kn->dep_map, _RET_IP_);
rwsem_release(&kn->dep_map, 1, _RET_IP_);
}
lock_acquired(&kn->dep_map, _RET_IP_);
rwsem_release(&kn->dep_map, 1, _RET_IP_);
}
/**

1
include/linux/kernfs.h
View file

@ -34,6 +34,7 @@ enum kernfs_node_type {
};
#define KERNFS_TYPE_MASK 0x000f
#define KERNFS_ACTIVE_REF KERNFS_FILE
#define KERNFS_FLAG_MASK ~KERNFS_TYPE_MASK
enum kernfs_node_flag {