[PATCH] drm/ttm: fix the tt_populated check in ttm_tt_destroy()

Ben Skeggs skeggsb at gmail.com
Mon Sep 16 21:21:15 PDT 2013

From: Ben Skeggs <bskeggs at redhat.com>

After a vmalloc failure in ttm_dma_tt_alloc_page_directory(),
ttm_dma_tt_init() will call ttm_tt_destroy() to cleanup, and end up
inside the driver's unpopulate() hook when populate() has never yet
been called.

On nouveau, the first issue to be hit because of this is that
dma_address[] may be a NULL pointer.  After working around this,
ttm_pool_unpopulate() may potentially hit the same issue with
the pages[] array.

It seems to make more sense to avoid calling unpopulate on already
unpopulated TTMs than to add checks to all the implementations.

Signed-off-by: Ben Skeggs <bskeggs at redhat.com>
Cc: Jerome Glisse <jglisse at redhat.com>
Cc: Thomas Hellstrom <thellstrom at vmware.com>
 drivers/gpu/drm/ttm/ttm_tt.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c
index 5e93a52..210d503 100644
--- a/drivers/gpu/drm/ttm/ttm_tt.c
+++ b/drivers/gpu/drm/ttm/ttm_tt.c
@@ -170,7 +170,7 @@ void ttm_tt_destroy(struct ttm_tt *ttm)
-	if (likely(ttm->pages != NULL)) {
+	if (ttm->state == tt_unbound) {

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