drm/nvc0/fb: take lock in nvc0_ram_put()

Kernel panic caused by list corruption in ltcg seems to indicate a
concurrency issue.

Take mutex of pfb like nv50_ram_put() to eliminate concurrency.

V2: Separate critical section into separate function, avoid taking the
    lock twice on NVC0

Signed-off-by: Roy Spliet <r.spliet@student.tudelft.nl>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

3 files changed, 26 insertions, 12 deletions

diff --git a/drivers/gpu/drm/nouveau/core/subdev/fb/priv.h b/drivers/gpu/drm/nouveau/core/subdev/fb/priv.h
index 6c974dd83e8b..db9d6ddde52c 100644
--- a/drivers/gpu/drm/nouveau/core/subdev/fb/priv.h
+++ b/drivers/gpu/drm/nouveau/core/subdev/fb/priv.h
@@ -81,7 +81,7 @@ void nv44_fb_tile_prog(struct nouveau_fb *, int, struct nouveau_fb_tile *);
 void nv46_fb_tile_init(struct nouveau_fb *, int i, u32 addr, u32 size,
                        u32 pitch, u32 flags, struct nouveau_fb_tile *);
 
-void nv50_ram_put(struct nouveau_fb *, struct nouveau_mem **);
+void __nv50_ram_put(struct nouveau_fb *, struct nouveau_mem *);
 extern int nv50_fb_memtype[0x80];
 
 #endif
diff --git a/drivers/gpu/drm/nouveau/core/subdev/fb/ramnv50.c b/drivers/gpu/drm/nouveau/core/subdev/fb/ramnv50.c
index af5aa7ee8ad9..903baff77fdd 100644
--- a/drivers/gpu/drm/nouveau/core/subdev/fb/ramnv50.c
+++ b/drivers/gpu/drm/nouveau/core/subdev/fb/ramnv50.c
@@ -27,17 +27,10 @@
 #include "priv.h"
 
 void
-nv50_ram_put(struct nouveau_fb *pfb, struct nouveau_mem **pmem)
+__nv50_ram_put(struct nouveau_fb *pfb, struct nouveau_mem *mem)
 {
         struct nouveau_mm_node *this;
-        struct nouveau_mem *mem;
 
-        mem = *pmem;
-        *pmem = NULL;
-        if (unlikely(mem == NULL))
-                return;
-
-        mutex_lock(&pfb->base.mutex);
         while (!list_empty(&mem->regions)) {
                 this = list_first_entry(&mem->regions, typeof(*this), rl_entry);
 
@@ -46,6 +39,19 @@ nv50_ram_put(struct nouveau_fb *pfb, struct nouveau_mem **pmem)
         }
 
         nouveau_mm_free(&pfb->tags, &mem->tag);
+}
+
+void
+nv50_ram_put(struct nouveau_fb *pfb, struct nouveau_mem **pmem)
+{
+        struct nouveau_mem *mem = *pmem;
+
+        *pmem = NULL;
+        if (unlikely(mem == NULL))
+                return;
+
+        mutex_lock(&pfb->base.mutex);
+        __nv50_ram_put(pfb, mem);
         mutex_unlock(&pfb->base.mutex);
 
         kfree(mem);
diff --git a/drivers/gpu/drm/nouveau/core/subdev/fb/ramnvc0.c b/drivers/gpu/drm/nouveau/core/subdev/fb/ramnvc0.c
index 9c3634acbb9d..cf97c4de4a6b 100644
--- a/drivers/gpu/drm/nouveau/core/subdev/fb/ramnvc0.c
+++ b/drivers/gpu/drm/nouveau/core/subdev/fb/ramnvc0.c
@@ -33,11 +33,19 @@ void
 nvc0_ram_put(struct nouveau_fb *pfb, struct nouveau_mem **pmem)
 {
         struct nouveau_ltcg *ltcg = nouveau_ltcg(pfb);
+        struct nouveau_mem *mem = *pmem;
 
-        if ((*pmem)->tag)
-                ltcg->tags_free(ltcg, &(*pmem)->tag);
+        *pmem = NULL;
+        if (unlikely(mem == NULL))
+                return;
 
-        nv50_ram_put(pfb, pmem);
+        mutex_lock(&pfb->base.mutex);
+        if (mem->tag)
+                ltcg->tags_free(ltcg, &mem->tag);
+        __nv50_ram_put(pfb, mem);
+        mutex_unlock(&pfb->base.mutex);
+
+        kfree(mem);
 }
 
 int