drm/nouveau: add per-channel mutex, use to lock access to drm's channel

This fixes a race condition between fbcon acceleration and TTM buffer
moves.  To reproduce:

- start X
- switch to vt and "while (true); do dmesg; done"
- switch to another vt and "sleep 2 && cat /path/to/debugfs/dri/0/evict_vram"
- switch back to vt running dmesg

We don't make use of this on any other channel yet, they're currently
protected by drm_global_mutex.  This will change in the near future.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

1 files changed, 14 insertions, 3 deletions

diff --git a/drivers/gpu/drm/nouveau/nouveau_fbcon.c b/drivers/gpu/drm/nouveau/nouveau_fbcon.c
index 22e83adcc930..bc30dbe11d00 100644
--- a/drivers/gpu/drm/nouveau/nouveau_fbcon.c
+++ b/drivers/gpu/drm/nouveau/nouveau_fbcon.c
@@ -62,11 +62,13 @@ nouveau_fbcon_fillrect(struct fb_info *info, const struct fb_fillrect *rect)
 
         ret = -ENODEV;
         if (!in_interrupt() && !(info->flags & FBINFO_HWACCEL_DISABLED)) {
+                mutex_lock(&dev_priv->channel->mutex);
                 if (dev_priv->card_type < NV_50)
                         ret = nv04_fbcon_fillrect(info, rect);
                 else
                 if (dev_priv->card_type < NV_C0)
                         ret = nv50_fbcon_fillrect(info, rect);
+                mutex_unlock(&dev_priv->channel->mutex);
         }
 
         if (ret == 0)
@@ -90,11 +92,13 @@ nouveau_fbcon_copyarea(struct fb_info *info, const struct fb_copyarea *image)
 
         ret = -ENODEV;
         if (!in_interrupt() && !(info->flags & FBINFO_HWACCEL_DISABLED)) {
+                mutex_lock(&dev_priv->channel->mutex);
                 if (dev_priv->card_type < NV_50)
                         ret = nv04_fbcon_copyarea(info, image);
                 else
                 if (dev_priv->card_type < NV_C0)
                         ret = nv50_fbcon_copyarea(info, image);
+                mutex_unlock(&dev_priv->channel->mutex);
         }
 
         if (ret == 0)
@@ -118,11 +122,13 @@ nouveau_fbcon_imageblit(struct fb_info *info, const struct fb_image *image)
 
         ret = -ENODEV;
         if (!in_interrupt() && !(info->flags & FBINFO_HWACCEL_DISABLED)) {
+                mutex_lock(&dev_priv->channel->mutex);
                 if (dev_priv->card_type < NV_50)
                         ret = nv04_fbcon_imageblit(info, image);
                 else
                 if (dev_priv->card_type < NV_C0)
                         ret = nv50_fbcon_imageblit(info, image);
+                mutex_unlock(&dev_priv->channel->mutex);
         }
 
         if (ret == 0)
@@ -142,12 +148,15 @@ nouveau_fbcon_sync(struct fb_info *info)
         struct nouveau_channel *chan = dev_priv->channel;
         int ret, i;
 
-        if (!chan || !chan->accel_done ||
+        if (!chan || !chan->accel_done || in_interrupt() ||
             info->state != FBINFO_STATE_RUNNING ||
             info->flags & FBINFO_HWACCEL_DISABLED)
                 return 0;
 
-        if (RING_SPACE(chan, 4)) {
+        mutex_lock(&chan->mutex);
+        ret = RING_SPACE(chan, 4);
+        if (ret) {
+                mutex_unlock(&chan->mutex);
                 nouveau_fbcon_gpu_lockup(info);
                 return 0;
         }
@@ -158,6 +167,7 @@ nouveau_fbcon_sync(struct fb_info *info)
         OUT_RING(chan, 0);
         nouveau_bo_wr32(chan->notifier_bo, chan->m2mf_ntfy + 3, 0xffffffff);
         FIRE_RING(chan);
+        mutex_unlock(&chan->mutex);
 
         ret = -EBUSY;
         for (i = 0; i < 100000; i++) {
@@ -353,6 +363,8 @@ nouveau_fbcon_create(struct nouveau_fbdev *nfbdev,
         info->pixmap.flags = FB_PIXMAP_SYSTEM;
         info->pixmap.scan_align = 1;
 
+        mutex_unlock(&dev->struct_mutex);
+
         if (dev_priv->channel && !nouveau_nofbaccel) {
                 ret = -ENODEV;
                 if (dev_priv->card_type < NV_50)
@@ -373,7 +385,6 @@ nouveau_fbcon_create(struct nouveau_fbdev *nfbdev,
                                                 nouveau_fb->base.height,
                                                 nvbo->bo.offset, nvbo);
 
-        mutex_unlock(&dev->struct_mutex);
         vga_switcheroo_client_fb_set(dev->pdev, info);
         return 0;