This patch tries to implement the synchronize_cbs() for ccw. For the
vring_interrupt() that is called via virtio_airq_handler(), the
synchronization is simply done via the airq_info's lock. For the
vring_interrupt() that is called via virtio_ccw_int_handler(), a per
device spinlock for irq is introduced ans used in the synchronization
method.
Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: Peter Zijlstra <peterz at infradead.org>
Cc: "Paul E. McKenney" <paulmck at kernel.org>
Cc: Marc Zyngier <maz at kernel.org>
Cc: Halil Pasic <pasic at linux.ibm.com>
Cc: Cornelia Huck <cohuck at redhat.com>
Signed-off-by: Jason Wang <jasowang at redhat.com>
---
drivers/s390/virtio/virtio_ccw.c | 27 +++++++++++++++++++++++++++
1 file changed, 27 insertions(+)
diff --git a/drivers/s390/virtio/virtio_ccw.c b/drivers/s390/virtio/virtio_ccw.c
index d35e7a3f7067..001e1f0e6037 100644
--- a/drivers/s390/virtio/virtio_ccw.c
+++ b/drivers/s390/virtio/virtio_ccw.c
@@ -62,6 +62,7 @@ struct virtio_ccw_device {
unsigned int revision; /* Transport revision */
wait_queue_head_t wait_q;
spinlock_t lock;
+ rwlock_t irq_lock;
struct mutex io_lock; /* Serializes I/O requests */
struct list_head virtqueues;
bool is_thinint;
@@ -984,6 +985,27 @@ static const char *virtio_ccw_bus_name(struct virtio_device
*vdev)
return dev_name(&vcdev->cdev->dev);
}
+static void virtio_ccw_synchronize_cbs(struct virtio_device *vdev)
+{
+ struct virtio_ccw_device *vcdev = to_vc_device(vdev);
+ struct airq_info *info = vcdev->airq_info;
+
+ if (info) {
+ /*
+ * Synchronize with the vring_interrupt() with airq indicator
+ */
+ write_lock(&info->lock);
+ write_unlock(&info->lock);
+ } else {
+ /*
+ * Synchronize with the vring_interrupt() called by
+ * virtio_ccw_int_handler().
+ */
+ write_lock(&vcdev->irq_lock);
+ write_unlock(&vcdev->irq_lock);
+ }
+}
+
static const struct virtio_config_ops virtio_ccw_config_ops = {
.get_features = virtio_ccw_get_features,
.finalize_features = virtio_ccw_finalize_features,
@@ -995,6 +1017,7 @@ static const struct virtio_config_ops virtio_ccw_config_ops
= {
.find_vqs = virtio_ccw_find_vqs,
.del_vqs = virtio_ccw_del_vqs,
.bus_name = virtio_ccw_bus_name,
+ .synchronize_cbs = virtio_ccw_synchronize_cbs,
};
@@ -1079,6 +1102,7 @@ static void virtio_ccw_int_handler(struct ccw_device
*cdev,
{
__u32 activity = intparm & VIRTIO_CCW_INTPARM_MASK;
struct virtio_ccw_device *vcdev = dev_get_drvdata(&cdev->dev);
+ unsigned long flags;
int i;
struct virtqueue *vq;
@@ -1106,6 +1130,7 @@ static void virtio_ccw_int_handler(struct ccw_device
*cdev,
vcdev->err = -EIO;
}
virtio_ccw_check_activity(vcdev, activity);
+ read_lock_irqsave(&vcdev->irq_lock, flags);
for_each_set_bit(i, indicators(vcdev),
sizeof(*indicators(vcdev)) * BITS_PER_BYTE) {
/* The bit clear must happen before the vring kick. */
@@ -1114,6 +1139,7 @@ static void virtio_ccw_int_handler(struct ccw_device
*cdev,
vq = virtio_ccw_vq_by_ind(vcdev, i);
vring_interrupt(0, vq);
}
+ read_unlock_irqrestore(&vcdev->irq_lock, flags);
if (test_bit(0, indicators2(vcdev))) {
virtio_config_changed(&vcdev->vdev);
clear_bit(0, indicators2(vcdev));
@@ -1284,6 +1310,7 @@ static int virtio_ccw_online(struct ccw_device *cdev)
init_waitqueue_head(&vcdev->wait_q);
INIT_LIST_HEAD(&vcdev->virtqueues);
spin_lock_init(&vcdev->lock);
+ rwlock_init(&vcdev->irq_lock);
mutex_init(&vcdev->io_lock);
spin_lock_irqsave(get_ccwdev_lock(cdev), flags);
--
2.25.1
Michael S. Tsirkin
2022-May-10 11:27 UTC
[PATCH V4 6/9] virtio-ccw: implement synchronize_cbs()
On Sat, May 07, 2022 at 03:19:51PM +0800, Jason Wang wrote:> This patch tries to implement the synchronize_cbs() for ccw. For the > vring_interrupt() that is called via virtio_airq_handler(), the > synchronization is simply done via the airq_info's lock. For the > vring_interrupt() that is called via virtio_ccw_int_handler(), a per > device spinlock for irq is introduced ans used in the synchronization > method. > > Cc: Thomas Gleixner <tglx at linutronix.de> > Cc: Peter Zijlstra <peterz at infradead.org> > Cc: "Paul E. McKenney" <paulmck at kernel.org> > Cc: Marc Zyngier <maz at kernel.org> > Cc: Halil Pasic <pasic at linux.ibm.com> > Cc: Cornelia Huck <cohuck at redhat.com> > Signed-off-by: Jason Wang <jasowang at redhat.com> > --- > drivers/s390/virtio/virtio_ccw.c | 27 +++++++++++++++++++++++++++ > 1 file changed, 27 insertions(+) > > diff --git a/drivers/s390/virtio/virtio_ccw.c b/drivers/s390/virtio/virtio_ccw.c > index d35e7a3f7067..001e1f0e6037 100644 > --- a/drivers/s390/virtio/virtio_ccw.c > +++ b/drivers/s390/virtio/virtio_ccw.c > @@ -62,6 +62,7 @@ struct virtio_ccw_device { > unsigned int revision; /* Transport revision */ > wait_queue_head_t wait_q; > spinlock_t lock; > + rwlock_t irq_lock; > struct mutex io_lock; /* Serializes I/O requests */ > struct list_head virtqueues; > bool is_thinint; > @@ -984,6 +985,27 @@ static const char *virtio_ccw_bus_name(struct virtio_device *vdev) > return dev_name(&vcdev->cdev->dev); > } > > +static void virtio_ccw_synchronize_cbs(struct virtio_device *vdev) > +{ > + struct virtio_ccw_device *vcdev = to_vc_device(vdev); > + struct airq_info *info = vcdev->airq_info; > + > + if (info) { > + /* > + * Synchronize with the vring_interrupt() with airq indicator > + */ > + write_lock(&info->lock); > + write_unlock(&info->lock); > + } else { > + /* > + * Synchronize with the vring_interrupt() called by > + * virtio_ccw_int_handler(). > + */ > + write_lock(&vcdev->irq_lock); > + write_unlock(&vcdev->irq_lock); > + } > +} > + > static const struct virtio_config_ops virtio_ccw_config_ops = { > .get_features = virtio_ccw_get_features, > .finalize_features = virtio_ccw_finalize_features, > @@ -995,6 +1017,7 @@ static const struct virtio_config_ops virtio_ccw_config_ops = { > .find_vqs = virtio_ccw_find_vqs, > .del_vqs = virtio_ccw_del_vqs, > .bus_name = virtio_ccw_bus_name, > + .synchronize_cbs = virtio_ccw_synchronize_cbs, > }; > > > @@ -1079,6 +1102,7 @@ static void virtio_ccw_int_handler(struct ccw_device *cdev, > { > __u32 activity = intparm & VIRTIO_CCW_INTPARM_MASK; > struct virtio_ccw_device *vcdev = dev_get_drvdata(&cdev->dev); > + unsigned long flags; > int i; > struct virtqueue *vq; > > @@ -1106,6 +1130,7 @@ static void virtio_ccw_int_handler(struct ccw_device *cdev, > vcdev->err = -EIO; > } > virtio_ccw_check_activity(vcdev, activity); > + read_lock_irqsave(&vcdev->irq_lock, flags); > for_each_set_bit(i, indicators(vcdev), > sizeof(*indicators(vcdev)) * BITS_PER_BYTE) { > /* The bit clear must happen before the vring kick. */Cornelia sent a lockdep trace on this. Basically I think this gets the irqsave/restore logic wrong. It attempts to disable irqs in the handler (which is an interrupt anyway). And it does not disable irqs in the synchronize_cbs. As a result in interrupt might try to take a read lock while .synchronize_cbs has the writer lock, resulting in a deadlock. I think you want regular read_lock + write_lock_irq.> @@ -1114,6 +1139,7 @@ static void virtio_ccw_int_handler(struct ccw_device *cdev, > vq = virtio_ccw_vq_by_ind(vcdev, i); > vring_interrupt(0, vq); > } > + read_unlock_irqrestore(&vcdev->irq_lock, flags); > if (test_bit(0, indicators2(vcdev))) { > virtio_config_changed(&vcdev->vdev); > clear_bit(0, indicators2(vcdev)); > @@ -1284,6 +1310,7 @@ static int virtio_ccw_online(struct ccw_device *cdev) > init_waitqueue_head(&vcdev->wait_q); > INIT_LIST_HEAD(&vcdev->virtqueues); > spin_lock_init(&vcdev->lock); > + rwlock_init(&vcdev->irq_lock); > mutex_init(&vcdev->io_lock); > > spin_lock_irqsave(get_ccwdev_lock(cdev), flags); > -- > 2.25.1