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Commit cdac75e6 authored by Davide Libenzi's avatar Davide Libenzi Committed by Linus Torvalds
Browse files

epoll: avoid kmemcheck warning 



Epoll calls rb_set_parent(n, n) to initialize the rb-tree node, but
rb_set_parent() accesses node's pointer in its code.  This creates a
warning in kmemcheck (reported by Vegard Nossum) about an uninitialized
memory access.  The warning is harmless since the following rb-tree node
insert is going to overwrite the node data.  In any case I think it's
better to not have that happening at all, and fix it by simplifying the
code to get rid of a few lines that became superfluous after the previous
epoll changes.

Signed-off-by: default avatarDavide Libenzi <davidel@xmailserver.org>
Cc: Vegard Nossum <vegard.nossum@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent b781ecb6

fs/eventpoll.c

+3 −24
Original line number Diff line number Diff line
@@ -257,25 +257,6 @@ static inline int ep_cmp_ffd(struct epoll_filefd *p1, 
	        (p1->file < p2->file ? -1 : p1->fd - p2->fd));

}



/* Special initialization for the RB tree node to detect linkage */

static inline void ep_rb_initnode(struct rb_node *n)

{

	rb_set_parent(n, n);

}



/* Removes a node from the RB tree and marks it for a fast is-linked check */

static inline void ep_rb_erase(struct rb_node *n, struct rb_root *r)

{

	rb_erase(n, r);

	rb_set_parent(n, n);

}



/* Fast check to verify that the item is linked to the main RB tree */

static inline int ep_rb_linked(struct rb_node *n)

{

	return rb_parent(n) != n;

}



/* Tells us if the item is currently linked */

static inline int ep_is_linked(struct list_head *p)

{
@@ -411,8 +392,7 @@ static int ep_remove(struct eventpoll *ep, struct epitem *epi) 
		list_del_init(&epi->fllink);

	spin_unlock(&file->f_ep_lock);



	if (ep_rb_linked(&epi->rbn))

		ep_rb_erase(&epi->rbn, &ep->rbr);

	rb_erase(&epi->rbn, &ep->rbr);



	spin_lock_irqsave(&ep->lock, flags);

	if (ep_is_linked(&epi->rdllink))
@@ -728,7 +708,6 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event, 
		goto error_return;



	/* Item initialization follow here ... */

	ep_rb_initnode(&epi->rbn);

	INIT_LIST_HEAD(&epi->rdllink);

	INIT_LIST_HEAD(&epi->fllink);

	INIT_LIST_HEAD(&epi->pwqlist);