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Commit e77e5481 authored by Linus Torvalds's avatar Linus Torvalds Committed by Greg Kroah-Hartman
Browse files

list: add "list_del_init_careful()" to go with "list_empty_careful()" 



[ Upstream commit c6fe44d96fc1536af5b11cd859686453d1b7bfd1 ]

That gives us ordering guarantees around the pair.

Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Stable-dep-of: 2192bba03d80 ("epoll: ep_autoremove_wake_function should use list_del_init_careful")
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent c32ab1c1

include/linux/list.h

+19 −1
Original line number Original line Diff line number Diff line
@@ -268,6 +268,24 @@ static inline int list_empty(const struct list_head *head) 
	return READ_ONCE(head->next) == head;

	return READ_ONCE(head->next) == head;

}

}





/**

 * list_del_init_careful - deletes entry from list and reinitialize it.

 * @entry: the element to delete from the list.

 *

 * This is the same as list_del_init(), except designed to be used

 * together with list_empty_careful() in a way to guarantee ordering

 * of other memory operations.

 *

 * Any memory operations done before a list_del_init_careful() are

 * guaranteed to be visible after a list_empty_careful() test.

 */

static inline void list_del_init_careful(struct list_head *entry)

{

	__list_del_entry(entry);

	entry->prev = entry;

	smp_store_release(&entry->next, entry);

}



/**

/**

 * list_empty_careful - tests whether a list is empty and not being modified

 * list_empty_careful - tests whether a list is empty and not being modified

 * @head: the list to test

 * @head: the list to test
@@ -283,7 +301,7 @@ static inline int list_empty(const struct list_head *head) 
 */

 */

static inline int list_empty_careful(const struct list_head *head)

static inline int list_empty_careful(const struct list_head *head)

{

{

	struct list_head *next = head->next;

	struct list_head *next = smp_load_acquire(&head->next);

	return (next == head) && (next == head->prev);

	return (next == head) && (next == head->prev);

}

}

kernel/sched/wait.c

+1 −1
Original line number Original line Diff line number Diff line
@@ -384,7 +384,7 @@ int autoremove_wake_function(struct wait_queue_entry *wq_entry, unsigned mode, i 
	int ret = default_wake_function(wq_entry, mode, sync, key);

	int ret = default_wake_function(wq_entry, mode, sync, key);





	if (ret)

	if (ret)

		list_del_init(&wq_entry->entry);

		list_del_init_careful(&wq_entry->entry);





	return ret;

	return ret;

}

}

mm/filemap.c

+1 −6
Original line number Original line Diff line number Diff line
@@ -1085,13 +1085,8 @@ static int wake_page_function(wait_queue_entry_t *wait, unsigned mode, int sync, 
	 * since after list_del_init(&wait->entry) the wait entry

	 * since after list_del_init(&wait->entry) the wait entry

	 * might be de-allocated and the process might even have

	 * might be de-allocated and the process might even have

	 * exited.

	 * exited.

	 *

	 * We _really_ should have a "list_del_init_careful()" to

	 * properly pair with the unlocked "list_empty_careful()"

	 * in finish_wait().

	 */

	 */

	smp_mb();

	list_del_init_careful(&wait->entry);

	list_del_init(&wait->entry);

	return ret;

	return ret;

}

}