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| author | Hugh Dickins <hughd@google.com> | 2012-03-21 16:34:20 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-03-21 17:55:01 -0700 |
| commit | 9f7de8275b46d9d11b1505adbfe6c2bb48df4741 (patch) | |
| tree | 7495111b20585e6e4da20d1b46b7a3747903ce2a /lib/idr.c | |
| parent | 0e79dedde951e981612ed4e6d74873d61d2a113b (diff) | |
| download | lwn-9f7de8275b46d9d11b1505adbfe6c2bb48df4741.tar.gz lwn-9f7de8275b46d9d11b1505adbfe6c2bb48df4741.zip | |
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>
Diffstat (limited to 'lib/idr.c')
| -rw-r--r-- | lib/idr.c | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/lib/idr.c b/lib/idr.c index ed055b297c81..12499ba7967e 100644 --- a/lib/idr.c +++ b/lib/idr.c @@ -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) { |