Re: [PATCH] rcu: Fix wrong check in list_splice_init_rcu()
From: Paul E. McKenney
Date: Tue Jul 19 2011 - 16:28:17 EST
On Tue, Jul 19, 2011 at 09:10:26PM +0200, Jan H. Schönherr wrote:
> If I don't miss something obvious, the following patch would
> be a good idea.
> There are currently two users of list_splice_init_rcu(): IPMI and btrfs.
> For these, list_splice_init_rcu() is currently a NOP.
> If I interpret the code correctly, this fixes a memory leak for
> IPMI and something probably worse for btrfs.
> The call from within btrfs was introduced only after v2.6.39 with commit
> 1f78160 ("Btrfs: using rcu lock in the reader side of devices list") by
> converting a list_splice_init() call.
> Therefore, this patch might be a candidate for v3.0.
Excellent catch! This one has been around for some time, so my guess
is that it goes into v3.1. Either way, I have queued it, thank you!
> From: Jan H. Schönherr <schnhrr@xxxxxxxxxxxxxxx>
> Splicing something into an empty list should work, while there is
> nothing to do if the source list is empty.
> Signed-off-by: Jan H. Schönherr <schnhrr@xxxxxxxxxxxxxxx>
> include/linux/rculist.h | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
> diff --git a/include/linux/rculist.h b/include/linux/rculist.h
> index e3beb31..d079290 100644
> --- a/include/linux/rculist.h
> +++ b/include/linux/rculist.h
> @@ -183,7 +183,7 @@ static inline void list_splice_init_rcu(struct list_head *list,
> struct list_head *last = list->prev;
> struct list_head *at = head->next;
> - if (list_empty(head))
> + if (list_empty(list))
> /* "first" and "last" tracking list, so initialize it. */
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