On Sat, Jul 23, 2016 at 09:42:35AM +0200, Vegard Nossum wrote:
> I was seeing a lot of these:
>
> BUG: sleeping function called from invalid context at mm/slab.h:388
> in_atomic(): 0, irqs_disabled(): 0, pid: 14971, name: trinity-c2
> Preemption disabled at:[<ffffffff819bcd46>] rhashtable_walk_start+0x46/0x150
>
> [<ffffffff81149abb>] preempt_count_add+0x1fb/0x280
> [<ffffffff83295722>] _raw_spin_lock+0x12/0x40
> [<ffffffff811aac87>] console_unlock+0x2f7/0x930
> [<ffffffff811ab5bb>] vprintk_emit+0x2fb/0x520
> [<ffffffff811aba6a>] vprintk_default+0x1a/0x20
> [<ffffffff812c171a>] printk+0x94/0xb0
> [<ffffffff811d6ed0>] print_stack_trace+0xe0/0x170
> [<ffffffff8115835e>] ___might_sleep+0x3be/0x460
> [<ffffffff81158490>] __might_sleep+0x90/0x1a0
> [<ffffffff8139b823>] kmem_cache_alloc+0x153/0x1e0
> [<ffffffff819bca1e>] rhashtable_walk_init+0xfe/0x2d0
> [<ffffffff82ec64de>] sctp_transport_walk_start+0x1e/0x60
> [<ffffffff82edd8ad>] sctp_transport_seq_start+0x4d/0x150
> [<ffffffff8143a82b>] seq_read+0x27b/0x1180
> [<ffffffff814f97fc>] proc_reg_read+0xbc/0x180
> [<ffffffff813d471b>] __vfs_read+0xdb/0x610
> [<ffffffff813d4d3a>] vfs_read+0xea/0x2d0
> [<ffffffff813d615b>] SyS_pread64+0x11b/0x150
> [<ffffffff8100334c>] do_syscall_64+0x19c/0x410
> [<ffffffff832960a5>] return_from_SYSCALL_64+0x0/0x6a
> [<ffffffffffffffff>] 0xffffffffffffffff
>
> Apparently we always need to call rhashtable_walk_stop(), even when
> rhashtable_walk_start() fails:
>
> * rhashtable_walk_start - Start a hash table walk
> * @iter: Hash table iterator
> *
> * Start a hash table walk. Note that we take the RCU lock in all
> * cases including when we return an error. So you must always call
> * rhashtable_walk_stop to clean up.
>
> otherwise we never call rcu_read_unlock() and we get the splat above.
>
> See-also: 53fa1036 ("sctp: fix some rhashtable functions using in sctp proc/diag")
> See-also: f2dba9c6 ("rhashtable: Introduce rhashtable_walk_*")
> Cc: Xin Long <lucien.xin@xxxxxxxxx>
> Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Vegard Nossum <vegard.nossum@xxxxxxxxxx>
> ---
> net/sctp/socket.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/net/sctp/socket.c b/net/sctp/socket.c
> index 67154b8..7f5689a 100644
> --- a/net/sctp/socket.c
> +++ b/net/sctp/socket.c
> @@ -4301,6 +4301,7 @@ int sctp_transport_walk_start(struct rhashtable_iter *iter)
>
> err = rhashtable_walk_start(iter);
> if (err && err != -EAGAIN) {
> + rhashtable_walk_stop(iter);
> rhashtable_walk_exit(iter);
I was doubt now if we shouldn't just call sctp_transport_walk_stop()
instead, but maybe it's good to keep the two apart, error handling from
actual stop.
I think this one deserves a Fixes tag because prior to 53fa1036 it was
okay.
Fixes: 53fa1036 ("sctp: fix some rhashtable functions using in sctp proc/diag")
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>
> return err;
> }
> --
> 1.9.1
>
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