Messages in this thread | | | Date | Thu, 13 May 2010 07:50:50 +0300 | From | "Michael S. Tsirkin" <> | Subject | Re: [PATCH RFC tip/core/rcu 23/23] vhost: add __rcu annotations |
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On Wed, May 12, 2010 at 04:00:57PM -0700, Paul E. McKenney wrote: > On Thu, May 13, 2010 at 12:48:47AM +0300, Michael S. Tsirkin wrote: > > On Wed, May 12, 2010 at 02:33:42PM -0700, Paul E. McKenney wrote: > > > From: Arnd Bergmann <arnd@relay.de.ibm.com> > > > > > > Also add rcu_dreference_protected() for code paths where locks are held. > > > > > > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > > > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > > > Cc: "Michael S. Tsirkin" <mst@redhat.com> > > > > Maybe long lines can be fixed? Otherwise looks ok. > > Done. I introduced locals to make it fit.
Just pls check this does not lead to unused variable warnings when the whole lockdep is off.
> One other thing... We need some API that says "we are running in the > context of a work queue." Otherwise, we will get false positives when > called in a work queue without locks held. > > Any thoughts? One approach would be to create a separate lockdep class > for vhost workqueue state, similar to the approach used in instrument > rcu_read_lock() and friends. > > Thanx, Paul > > > > --- > > > drivers/vhost/net.c | 11 ++++++++--- > > > drivers/vhost/vhost.c | 14 ++++++++------ > > > drivers/vhost/vhost.h | 4 ++-- > > > 3 files changed, 18 insertions(+), 11 deletions(-) > > > > > > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c > > > index 9777583..945c5cb 100644 > > > --- a/drivers/vhost/net.c > > > +++ b/drivers/vhost/net.c > > > @@ -364,7 +364,10 @@ static void vhost_net_disable_vq(struct vhost_net *n, > > > static void vhost_net_enable_vq(struct vhost_net *n, > > > struct vhost_virtqueue *vq) > > > { > > > - struct socket *sock = vq->private_data; > > > + struct socket *sock; > > > + > > > + sock = rcu_dereference_protected(vq->private_data, > > > + lockdep_is_held(&vq->mutex)); > > > if (!sock) > > > return; > > > if (vq == n->vqs + VHOST_NET_VQ_TX) { > > > @@ -380,7 +383,8 @@ static struct socket *vhost_net_stop_vq(struct vhost_net *n, > > > struct socket *sock; > > > > > > mutex_lock(&vq->mutex); > > > - sock = vq->private_data; > > > + sock = rcu_dereference_protected(vq->private_data, > > > + lockdep_is_held(&vq->mutex)); > > > vhost_net_disable_vq(n, vq); > > > rcu_assign_pointer(vq->private_data, NULL); > > > mutex_unlock(&vq->mutex); > > > @@ -518,7 +522,8 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd) > > > } > > > > > > /* start polling new socket */ > > > - oldsock = vq->private_data; > > > + oldsock = rcu_dereference_protected(vq->private_data, > > > + lockdep_is_held(&vq->mutex)); > > > if (sock == oldsock) > > > goto done; > > > > > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > > > index e69d238..fc0c077 100644 > > > --- a/drivers/vhost/vhost.c > > > +++ b/drivers/vhost/vhost.c > > > @@ -180,7 +180,7 @@ long vhost_dev_reset_owner(struct vhost_dev *dev) > > > vhost_dev_cleanup(dev); > > > > > > memory->nregions = 0; > > > - dev->memory = memory; > > > + RCU_INIT_POINTER(dev->memory, memory); > > > return 0; > > > } > > > > > > @@ -212,8 +212,9 @@ void vhost_dev_cleanup(struct vhost_dev *dev) > > > fput(dev->log_file); > > > dev->log_file = NULL; > > > /* No one will access memory at this point */ > > > - kfree(dev->memory); > > > - dev->memory = NULL; > > > + kfree(rcu_dereference_protected(dev->memory, > > > + lockdep_is_held(&dev->mutex))); > > > + RCU_INIT_POINTER(dev->memory, NULL); > > > if (dev->mm) > > > mmput(dev->mm); > > > dev->mm = NULL; > > > @@ -294,14 +295,14 @@ static int vq_access_ok(unsigned int num, > > > /* Caller should have device mutex but not vq mutex */ > > > int vhost_log_access_ok(struct vhost_dev *dev) > > > { > > > - return memory_access_ok(dev, dev->memory, 1); > > > + return memory_access_ok(dev, rcu_dereference_protected(dev->memory, lockdep_is_held(&dev->mutex)), 1); > > > } > > > > > > /* Verify access for write logging. */ > > > /* Caller should have vq mutex and device mutex */ > > > static int vq_log_access_ok(struct vhost_virtqueue *vq, void __user *log_base) > > > { > > > - return vq_memory_access_ok(log_base, vq->dev->memory, > > > + return vq_memory_access_ok(log_base, rcu_dereference_protected(vq->dev->memory, lockdep_is_held(&dev->mutex)), > > > vhost_has_feature(vq->dev, VHOST_F_LOG_ALL)) && > > > (!vq->log_used || log_access_ok(log_base, vq->log_addr, > > > sizeof *vq->used + > > > @@ -342,7 +343,8 @@ static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m) > > > > > > if (!memory_access_ok(d, newmem, vhost_has_feature(d, VHOST_F_LOG_ALL))) > > > return -EFAULT; > > > - oldmem = d->memory; > > > + oldmem = rcu_dereference_protected(d->memory, > > > + lockdep_is_held(&d->mutex)); > > > rcu_assign_pointer(d->memory, newmem); > > > synchronize_rcu(); > > > kfree(oldmem); > > > diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h > > > index 44591ba..240396c 100644 > > > --- a/drivers/vhost/vhost.h > > > +++ b/drivers/vhost/vhost.h > > > @@ -92,7 +92,7 @@ struct vhost_virtqueue { > > > * work item execution acts instead of rcu_read_lock() and the end of > > > * work item execution acts instead of rcu_read_lock(). > > > * Writers use virtqueue mutex. */ > > > - void *private_data; > > > + void __rcu *private_data; > > > /* Log write descriptors */ > > > void __user *log_base; > > > struct vhost_log log[VHOST_NET_MAX_SG]; > > > @@ -102,7 +102,7 @@ struct vhost_dev { > > > /* Readers use RCU to access memory table pointer > > > * log base pointer and features. > > > * Writers use mutex below.*/ > > > - struct vhost_memory *memory; > > > + struct vhost_memory __rcu *memory; > > > struct mm_struct *mm; > > > struct mutex mutex; > > > unsigned acked_features; > > > -- > > > 1.7.0.6
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