Messages in this thread | | | Date | Tue, 18 Jan 2011 19:55:00 +0200 | From | "Michael S. Tsirkin" <> | Subject | Re: [PATCH] vhost: rcu annotation fixup |
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On Tue, Jan 18, 2011 at 09:48:34AM -0800, Paul E. McKenney wrote: > 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@redhat.com> > > --- > > 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?
Yes, OK.
> 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
Hopefully, yes. We don't always have a lock: the idea was to create a lockdep for these cases. But we can't pass the pointer to that ...
> > return acked_features & (1 << bit); > > } > > > > -- > > 1.7.3.2.91.g446ac > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > Please read the FAQ at http://www.tux.org/lkml/
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