Mesa (master): i965: Don't try to unmap NULL program cache BO.

[Kenneth Graunke]

Module: Mesa
Branch: master
Commit: bc074a45180eddf30ea723bbdf89895e2c7684ca
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=bc074a45180eddf30ea723bbdf89895e2c7684ca

Author: Kenneth Graunke <kenneth at whitecape.org>
Date:   Wed May  3 19:24:32 2017 -0700

i965: Don't try to unmap NULL program cache BO.

When running shader-db with intel_stub and recent Mesa, context creation
fails when making a logical hardware context.  In this case, we call
intelDestroyContext(), which gets here and tries to unmap the cache BO.

But there isn't one - we haven't made it yet.  So we try to unmap a
NULL pointer, which used to be safe (it did nothing), but crashes
after commit 7c3b8ed87859bfdfb985d21685115a729f9cd138.

The result is that we crash rather than failing context creation with
a nice message.  Either way nothing works, but this is more polite.

Cc: "17.1" <mesa-stable at lists.freedesktop.org>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>

---

 src/mesa/drivers/dri/i965/brw_program_cache.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_program_cache.c b/src/mesa/drivers/dri/i965/brw_program_cache.c
index c06ee23781..b0e2962f88 100644
--- a/src/mesa/drivers/dri/i965/brw_program_cache.c
+++ b/src/mesa/drivers/dri/i965/brw_program_cache.c
@@ -485,10 +485,13 @@ brw_destroy_cache(struct brw_context *brw, struct brw_cache *cache)
 
    DBG("%s\n", __func__);
 
-   if (brw->has_llc)
-      brw_bo_unmap(cache->bo);
-   brw_bo_unreference(cache->bo);
-   cache->bo = NULL;
+   /* This can be NULL if context creation failed early on */
+   if (cache->bo) {
+      if (brw->has_llc)
+         brw_bo_unmap(cache->bo);
+      brw_bo_unreference(cache->bo);
+      cache->bo = NULL;
+   }
    brw_clear_cache(brw, cache);
    free(cache->items);
    cache->items = NULL;