On 3/23/2016 1:28 PM, Chris Wilson wrote:
On Wed, Mar 23, 2016 at 11:39:44AM +0530, akash.goel@xxxxxxxxx wrote:
+#ifdef CONFIG_MIGRATION
+static int i915_migratepage(struct address_space *mapping,
+ struct page *newpage, struct page *page,
+ enum migrate_mode mode, void *dev_priv_data)
If we move this to i915_gem_shrink_migratepage (i.e. i915_gem_shrink),
we can
+ /*
+ * Use trylock here, with a timeout, for struct_mutex as
+ * otherwise there is a possibility of deadlock due to lock
+ * inversion. This path, which tries to migrate a particular
+ * page after locking that page, can race with a path which
+ * truncate/purge pages of the corresponding object (after
+ * acquiring struct_mutex). Since page truncation will also
+ * try to lock the page, a scenario of deadlock can arise.
+ */
+ while (!mutex_trylock(&dev->struct_mutex) && --timeout)
+ schedule_timeout_killable(1);
replace this with i915_gem_shrinker_lock() and like constructs with the
other shrinkers.
fine, will rename the function to gem_shrink_migratepage, move it inside
the gem_shrinker.c file, and use the existing constructs.
> Any reason for dropping the early
> if (!page_private(obj)) skip?
>
Would this sequence be fine ?
if (!page_private(page))
goto migrate; /*skip */
Loop for locking mutex
obj = (struct drm_i915_gem_object *)page_private(page);
if (!PageSwapCache(page) && obj) {
Similarly there are other patterns here that would benefit from
integration with existing shrinker logic. However, things like tidying
up the pin_display, unbinding, rpm lock inversion are still only on
list.
Tidying, like split that one single if condition into multiple if, else
if blocks ?
Best regards
Akash
-Chris
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