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virtio: add debugging if driver doesn't kick.

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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>
This commit is contained in:
Rusty Russell 2012-01-12 15:44:43 +10:30
parent ee7cd8981e
commit e93300b1af
1 changed files with 31 additions and 0 deletions
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31
drivers/virtio/virtio_ring.c
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@ -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);