Commit 9f7de827 authored Mar 21, 2012 by Hugh Dickins Committed by Linus Torvalds Mar 21, 2012

idr: make idr_get_next() good for rcu_read_lock()



Make one small adjustment to idr_get_next(): take the height from the top
layer (stable under RCU) instead of from the root (unprotected by RCU), as
idr_find() does: so that it can be used with RCU locking.  Copied comment
on RCU locking from idr_find().

Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 0e79dedd

lib/idr.c

+5 −3

Original line number	Diff line number	Diff line
		@@ -595,8 +595,10 @@ EXPORT_SYMBOL(idr_for_each);
		* Returns pointer to registered object with id, which is next number to
		* given id. After being looked up, *@nextidp will be updated for the next
		* iteration.
		*
		* This function can be called under rcu_read_lock(), given that the leaf
		* pointers lifetimes are correctly managed.
		*/

		void idr_get_next(struct idr idp, int *nextidp)
		{
		struct idr_layer p, pa[MAX_LEVEL];
		@@ -605,11 +607,11 @@ void idr_get_next(struct idr idp, int *nextidp)
		int n, max;

		/* find first ent */
		n = idp->layers * IDR_BITS;
		max = 1 << n;
		p = rcu_dereference_raw(idp->top);
		if (!p)
		return NULL;
		n = (p->layer + 1) * IDR_BITS;
		max = 1 << n;

		while (id < max) {
		while (n > 0 && p) {