[Intel-gfx] [PATCH 31/61] drm/i915: Prepare for obj->mm.lock removal

Maarten Lankhorst
2020-10-02T13:00:14Z

From: Thomas Hellström <thomas.hellstrom@intel.com>

Stolen objects need to lock, and we may call put_pages when
refcount drops to 0, ensure all calls are handled correctly.

Idea-from: Thomas Hellström <thomas.hellstrom@intel.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
---
drivers/gpu/drm/i915/gem/i915_gem_object.h | 14 ++++++++++++++
drivers/gpu/drm/i915/gem/i915_gem_pages.c | 14 ++++++++++++--
drivers/gpu/drm/i915/gem/i915_gem_stolen.c | 10 +++++++++-
3 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.h b/drivers/gpu/drm/i915/gem/i915_gem_object.h
index 80424ce49f26..534e36b8d43b 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object.h
+++ b/drivers/gpu/drm/i915/gem/i915_gem_object.h
@@ -112,6 +112,20 @@ i915_gem_object_put(struct drm_i915_gem_object *obj)

#define assert_object_held(obj) dma_resv_assert_held((obj)->base.resv)

+/*
+ * If more than one potential simultaneous locker, assert held.
+ */
+static inline void assert_object_held_shared(struct drm_i915_gem_object *obj)
+{
+ /*
+ * Note mm list lookup is protected by
+ * kref_get_unless_zero().
+ */
+ if (IS_ENABLED(CONFIG_LOCKDEP) &&
+ kref_read(&obj->base.refcount) > 0)
+ lockdep_assert_held(&obj->mm.lock);
+}
+
static inline int __i915_gem_object_lock(struct drm_i915_gem_object *obj,
struct i915_gem_ww_ctx *ww,
bool intr)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pages.c b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
index 70d8e09a9188..75556c417873 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_pages.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
@@ -18,7 +18,7 @@ void __i915_gem_object_set_pages(struct drm_i915_gem_object *obj,
unsigned long supported = INTEL_INFO(i915)->page_sizes;
int i;

- lockdep_assert_held(&obj->mm.lock);
+ assert_object_held_shared(obj);

if (i915_gem_object_is_volatile(obj))
obj->mm.madv = I915_MADV_DONTNEED;
@@ -65,6 +65,7 @@ void __i915_gem_object_set_pages(struct drm_i915_gem_object *obj,
struct list_head *list;
unsigned long flags;

+ lockdep_assert_held(&obj->mm.lock);
spin_lock_irqsave(&i915->mm.obj_lock, flags);

i915->mm.shrink_count++;
@@ -86,6 +87,8 @@ int ____i915_gem_object_get_pages(struct drm_i915_gem_object *obj)
struct drm_i915_private *i915 = to_i915(obj->base.dev);
int err;

+ assert_object_held_shared(obj);
+
if (unlikely(obj->mm.madv != I915_MADV_WILLNEED)) {
drm_dbg(&i915->drm,
"Attempting to obtain a purgeable object\n");
@@ -113,6 +116,8 @@ int __i915_gem_object_get_pages(struct drm_i915_gem_object *obj)
if (err)
return err;

+ assert_object_held_shared(obj);
+
if (unlikely(!i915_gem_object_has_pages(obj))) {
GEM_BUG_ON(i915_gem_object_has_pinned_pages(obj));

@@ -140,7 +145,7 @@ void i915_gem_object_truncate(struct drm_i915_gem_object *obj)
/* Try to discard unwanted pages */
void i915_gem_object_writeback(struct drm_i915_gem_object *obj)
{
- lockdep_assert_held(&obj->mm.lock);
+ assert_object_held_shared(obj);
GEM_BUG_ON(i915_gem_object_has_pages(obj));

if (obj->ops->writeback)
@@ -171,6 +176,8 @@ __i915_gem_object_unset_pages(struct drm_i915_gem_object *obj)
{
struct sg_table *pages;

+ assert_object_held_shared(obj);
+
pages = fetch_and_zero(&obj->mm.pages);
if (IS_ERR_OR_NULL(pages))
return pages;
@@ -198,6 +205,9 @@ int __i915_gem_object_put_pages_locked(struct drm_i915_gem_object *obj)
if (i915_gem_object_has_pinned_pages(obj))
return -EBUSY;

+ /* May be called by shrinker from within get_pages() (on another bo) */
+ assert_object_held_shared(obj);
+
i915_gem_object_release_mmap_offset(obj);

/*
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_stolen.c b/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
index 9a9242b5a99f..1fd287ce86f4 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
@@ -593,11 +593,19 @@ __i915_gem_object_create_stolen(struct intel_memory_region *mem,
cache_level = HAS_LLC(mem->i915) ? I915_CACHE_LLC : I915_CACHE_NONE;
i915_gem_object_set_cache_coherency(obj, cache_level);

+ if (WARN_ON(!i915_gem_object_trylock(obj))) {
+ err = -EBUSY;
+ goto cleanup;
+ }
+
err = i915_gem_object_pin_pages(obj);
- if (err)
+ if (err) {
+ i915_gem_object_unlock(obj);
goto cleanup;
+ }

i915_gem_object_init_memory_region(obj, mem);
+ i915_gem_object_unlock(obj);

return obj;