drm/nouveau: Implement weak channel references.

nouveau_channel_ref() takes a "weak" channel reference that doesn't
prevent the hardware channel resources from being released, it just
keeps the channel data structure alive.

Signed-off-by: Francisco Jerez <currojerez@riseup.net>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

diff --git a/drivers/gpu/drm/nouveau/nouveau_channel.c b/drivers/gpu/drm/nouveau/nouveau_channel.c
index 38929fd..76033c5 100644 (file)
--- a/drivers/gpu/drm/nouveau/nouveau_channel.c
+++ b/drivers/gpu/drm/nouveau/nouveau_channel.c
@@ -125,7 +125,8 @@ nouveau_channel_alloc(struct drm_device *dev, struct nouveau_channel **chan_ret,
        chan->vram_handle = vram_handle;
        chan->gart_handle = gart_handle;
 
-       atomic_set(&chan->refcount, 1);
+       kref_init(&chan->ref);
+       atomic_set(&chan->users, 1);
        mutex_init(&chan->mutex);
        mutex_lock(&chan->mutex);
 
@@ -133,7 +134,7 @@ nouveau_channel_alloc(struct drm_device *dev, struct nouveau_channel **chan_ret,
        spin_lock_irqsave(&dev_priv->channels.lock, flags);
        for (chan->id = 0; chan->id < pfifo->channels; chan->id++) {
                if (!dev_priv->channels.ptr[chan->id]) {
-                       dev_priv->channels.ptr[chan->id] = chan;
+                       nouveau_channel_ref(chan, &dev_priv->channels.ptr[chan->id]);
                        break;
                }
        }
@@ -240,10 +241,12 @@ nouveau_channel_alloc(struct drm_device *dev, struct nouveau_channel **chan_ret,
 struct nouveau_channel *
 nouveau_channel_get_unlocked(struct nouveau_channel *ref)
 {
-       if (likely(ref && atomic_inc_not_zero(&ref->refcount)))
-               return ref;
+       struct nouveau_channel *chan = NULL;
 
-       return NULL;
+       if (likely(ref && atomic_inc_not_zero(&ref->users)))
+               nouveau_channel_ref(ref, &chan);
+
+       return chan;
 }
 
 struct nouveau_channel *
@@ -281,15 +284,14 @@ nouveau_channel_put_unlocked(struct nouveau_channel **pchan)
        int ret;
 
        /* decrement the refcount, and we're done if there's still refs */
-       if (likely(!atomic_dec_and_test(&chan->refcount))) {
-               *pchan = NULL;
+       if (likely(!atomic_dec_and_test(&chan->users))) {
+               nouveau_channel_ref(NULL, pchan);
                return;
        }
 
        /* noone wants the channel anymore */
        NV_DEBUG(dev, "freeing channel %d\n", chan->id);
        nouveau_debugfs_channel_fini(chan);
-       *pchan = NULL;
 
        /* give it chance to idle */
        nouveau_fence_update(chan);
@@ -333,7 +335,7 @@ nouveau_channel_put_unlocked(struct nouveau_channel **pchan)
         * remove it from the channel list
         */
        spin_lock_irqsave(&dev_priv->channels.lock, flags);
-       dev_priv->channels.ptr[chan->id] = NULL;
+       nouveau_channel_ref(NULL, &dev_priv->channels.ptr[chan->id]);
        spin_unlock_irqrestore(&dev_priv->channels.lock, flags);
 
        /* destroy any resources the channel owned */
@@ -345,10 +347,8 @@ nouveau_channel_put_unlocked(struct nouveau_channel **pchan)
        }
        nouveau_gpuobj_channel_takedown(chan);
        nouveau_notifier_takedown_channel(chan);
-       if (chan->user)
-               iounmap(chan->user);
 
-       kfree(chan);
+       nouveau_channel_ref(NULL, pchan);
 }
 
 void
@@ -358,6 +358,31 @@ nouveau_channel_put(struct nouveau_channel **pchan)
        nouveau_channel_put_unlocked(pchan);
 }
 
+static void
+nouveau_channel_del(struct kref *ref)
+{
+       struct nouveau_channel *chan =
+               container_of(ref, struct nouveau_channel, ref);
+
+       if (chan->user)
+               iounmap(chan->user);
+
+       kfree(chan);
+}
+
+void
+nouveau_channel_ref(struct nouveau_channel *chan,
+                   struct nouveau_channel **pchan)
+{
+       if (chan)
+               kref_get(&chan->ref);
+
+       if (*pchan)
+               kref_put(&(*pchan)->ref, nouveau_channel_del);
+
+       *pchan = chan;
+}
+
 /* cleans up all the fifos from file_priv */
 void
 nouveau_channel_cleanup(struct drm_device *dev, struct drm_file *file_priv)
@@ -373,7 +398,7 @@ nouveau_channel_cleanup(struct drm_device *dev, struct drm_file *file_priv)
                if (IS_ERR(chan))
                        continue;
 
-               atomic_dec(&chan->refcount);
+               atomic_dec(&chan->users);
                nouveau_channel_put(&chan);
        }
 }
@@ -427,7 +452,7 @@ nouveau_ioctl_fifo_alloc(struct drm_device *dev, void *data,
                                    &init->notifier_handle);
 
        if (ret == 0)
-               atomic_inc(&chan->refcount); /* userspace reference */
+               atomic_inc(&chan->users); /* userspace reference */
        nouveau_channel_put(&chan);
        return ret;
 }
@@ -443,7 +468,7 @@ nouveau_ioctl_fifo_free(struct drm_device *dev, void *data,
        if (IS_ERR(chan))
                return PTR_ERR(chan);
 
-       atomic_dec(&chan->refcount);
+       atomic_dec(&chan->users);
        nouveau_channel_put(&chan);
        return 0;
 }

diff --git a/drivers/gpu/drm/nouveau/nouveau_drv.h b/drivers/gpu/drm/nouveau/nouveau_drv.h
index e6708be..d152bc3 100644 (file)
--- a/drivers/gpu/drm/nouveau/nouveau_drv.h
+++ b/drivers/gpu/drm/nouveau/nouveau_drv.h
@@ -165,7 +165,11 @@ struct nouveau_channel {
        struct drm_device *dev;
        int id;
 
-       atomic_t refcount;
+       /* references to the channel data structure */
+       struct kref ref;
+       /* users of the hardware channel resources, the hardware
+        * context will be kicked off when it reaches zero. */
+       atomic_t users;
        struct mutex mutex;
 
        /* owner of this fifo */
@@ -808,6 +812,8 @@ extern struct nouveau_channel *
 nouveau_channel_get(struct drm_device *, struct drm_file *, int id);
 extern void nouveau_channel_put_unlocked(struct nouveau_channel **);
 extern void nouveau_channel_put(struct nouveau_channel **);
+extern void nouveau_channel_ref(struct nouveau_channel *chan,
+                               struct nouveau_channel **pchan);
 
 /* nouveau_object.c */
 extern int  nouveau_gpuobj_early_init(struct drm_device *);