On Tue, Jan 18, 2011 at 01:08:45PM +0200, Michael S. Tsirkin wrote:
> When built with rcu checks enabled, vhost triggers
> bogus warnings as vhost features are read without
> dev->mutex sometimes.
> Fixing it properly is not trivial as vhost.h does not
> know which lockdep classes it will be used under.
> Disable the warning by stubbing out the check for now.
>
> Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> ---
> drivers/vhost/vhost.h | 4 +---
> 1 files changed, 1 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
> index 2af44b7..2d03a31 100644
> --- a/drivers/vhost/vhost.h
> +++ b/drivers/vhost/vhost.h
> @@ -173,9 +173,7 @@ static inline int vhost_has_feature(struct vhost_dev *dev, int bit)
> {
> unsigned acked_features;
>
> - acked_features =
> - rcu_dereference_index_check(dev->acked_features,
> - lockdep_is_held(&dev->mutex));
> + acked_features = rcu_dereference_index_check(dev->acked_features, 1);
Ouch!!!
Could you please at least add a comment?
Alternatively, pass in the lock that is held and check for that? Given
that this is a static inline, the compiler should be able to optimize
the argument away when !PROVE_RCU, correct?
Thanx, Paul
> return acked_features & (1 << bit);
> }
>
> --
> 1.7.3.2.91.g446ac
> --
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