gpu: nvgpu: protect channel update callback access

Protect callback races from spurious gk20a channel updates by testing if
the channel update callback still exists when in the scheduled work
(instead of only when scheduling the work to the queue), and by
canceling the work when the channel is freed. Protect access to the
callback and its data by accessing them together inside
spinlock-protected regions.

Bug 200051384

Change-Id: Ib4e1571c35f662195e1dec1e362df32ddc099eb3
Signed-off-by: Konsta Holtta <kholtta@nvidia.com>
Reviewed-on: http://git-master/r/592026
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>
Tested-by: Terje Bergstrom <tbergstrom@nvidia.com>

1 files changed, 16 insertions, 2 deletions

diff --git a/drivers/gpu/nvgpu/gk20a/channel_gk20a.c b/drivers/gpu/nvgpu/gk20a/channel_gk20a.c
index f554cf77..f48ef35f 100644
--- a/drivers/gpu/nvgpu/gk20a/channel_gk20a.c
+++ b/drivers/gpu/nvgpu/gk20a/channel_gk20a.c
@@ -682,8 +682,11 @@ void gk20a_free_channel(struct channel_gk20a *ch, bool finish)
         else
                 gk20a_vm_put(ch_vm);
 
+        spin_lock(&ch->update_fn_lock);
         ch->update_fn = NULL;
         ch->update_fn_data = NULL;
+        spin_unlock(&ch->update_fn_lock);
+        cancel_work_sync(&ch->update_fn_work);
 
 unbind:
         if (gk20a_is_channel_marked_as_tsg(ch))
@@ -745,7 +748,16 @@ static void gk20a_channel_update_runcb_fn(struct work_struct *work)
 {
         struct channel_gk20a *ch =
                 container_of(work, struct channel_gk20a, update_fn_work);
-        ch->update_fn(ch, ch->update_fn_data);
+        void (*update_fn)(struct channel_gk20a *, void *);
+        void *update_fn_data;
+
+        spin_lock(&ch->update_fn_lock);
+        update_fn = ch->update_fn;
+        update_fn_data = ch->update_fn_data;
+        spin_unlock(&ch->update_fn_lock);
+
+        if (update_fn)
+                update_fn(ch, update_fn_data);
 }
 
 struct channel_gk20a *gk20a_open_new_channel_with_cb(struct gk20a *g,
@@ -755,8 +767,10 @@ struct channel_gk20a *gk20a_open_new_channel_with_cb(struct gk20a *g,
         struct channel_gk20a *ch = gk20a_open_new_channel(g);
 
         if (ch) {
+                spin_lock(&ch->update_fn_lock);
                 ch->update_fn = update_fn;
                 ch->update_fn_data = update_fn_data;
+                spin_unlock(&ch->update_fn_lock);
         }
 
         return ch;
@@ -811,7 +825,7 @@ struct channel_gk20a *gk20a_open_new_channel(struct gk20a *g)
 
         ch->update_fn = NULL;
         ch->update_fn_data = NULL;
-
+        spin_lock_init(&ch->update_fn_lock);
         INIT_WORK(&ch->update_fn_work, gk20a_channel_update_runcb_fn);
 
         return ch;