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authorRusty Russell <rusty@rustcorp.com.au>2012-01-12 15:44:43 +1030
committerRusty Russell <rusty@rustcorp.com.au>2012-01-12 15:44:43 +1030
commite93300b1afc7cd4fe1e741ceaf06714d060e88b8 (patch)
tree060bb46e8d7b570fa08df94aef1cf4cc3620f8c5 /drivers/virtio
parentee7cd8981e15bcb365fc762afe3fc47b8242f630 (diff)
virtio: add debugging if driver doesn't kick.
Under the existing #ifdef DEBUG, check that they don't have more than 1/10 of a second between an add_buf() and a virtqueue_notify()/virtqueue_kick_prepare() call. We could get false positives on a really busy system, but good for development. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Diffstat (limited to 'drivers/virtio')
-rw-r--r--drivers/virtio/virtio_ring.c31
1 files changed, 31 insertions, 0 deletions
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 36bb6a61372..79e1b292c03 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -22,6 +22,7 @@
#include <linux/device.h>
#include <linux/slab.h>
#include <linux/module.h>
+#include <linux/hrtimer.h>
/* virtio guest is communicating with a virtual "device" that actually runs on
* a host processor. Memory barriers are used to control SMP effects. */
@@ -108,6 +109,10 @@ struct vring_virtqueue
#ifdef DEBUG
/* They're supposed to lock for us. */
unsigned int in_use;
+
+ /* Figure out if their kicks are too delayed. */
+ bool last_add_time_valid;
+ ktime_t last_add_time;
#endif
/* Tokens for callbacks. */
@@ -198,6 +203,19 @@ int virtqueue_add_buf(struct virtqueue *_vq,
BUG_ON(data == NULL);
+#ifdef DEBUG
+ {
+ ktime_t now = ktime_get();
+
+ /* No kick or get, with .1 second between? Warn. */
+ if (vq->last_add_time_valid)
+ WARN_ON(ktime_to_ms(ktime_sub(now, vq->last_add_time))
+ > 100);
+ vq->last_add_time = now;
+ vq->last_add_time_valid = true;
+ }
+#endif
+
/* If the host supports indirect descriptor tables, and we have multiple
* buffers, then go indirect. FIXME: tune this threshold */
if (vq->indirect && (out + in) > 1 && vq->num_free) {
@@ -298,6 +316,14 @@ bool virtqueue_kick_prepare(struct virtqueue *_vq)
new = vq->vring.avail->idx;
vq->num_added = 0;
+#ifdef DEBUG
+ if (vq->last_add_time_valid) {
+ WARN_ON(ktime_to_ms(ktime_sub(ktime_get(),
+ vq->last_add_time)) > 100);
+ }
+ vq->last_add_time_valid = false;
+#endif
+
if (vq->event) {
needs_kick = vring_need_event(vring_avail_event(&vq->vring),
new, old);
@@ -435,6 +461,10 @@ void *virtqueue_get_buf(struct virtqueue *_vq, unsigned int *len)
virtio_mb(vq);
}
+#ifdef DEBUG
+ vq->last_add_time_valid = false;
+#endif
+
END_USE(vq);
return ret;
}
@@ -620,6 +650,7 @@ struct virtqueue *vring_new_virtqueue(unsigned int num,
list_add_tail(&vq->vq.list, &vdev->vqs);
#ifdef DEBUG
vq->in_use = false;
+ vq->last_add_time_valid = false;
#endif
vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC);