[PATCH 33/56] drm/i915: Introduce i915_address_space.mutex

Chris Wilson chris at chris-wilson.co.uk
Sun Jul 1 11:53:37 UTC 2018


Add a mutex into struct i915_address_space to be used while operating on
the vma and their lists for a particular vm. As this may be called from
the shrinker, we taint the mutex with fs_reclaim so that from the start
lockdep warns us if we are caught holding the mutex across an
allocation. (With such small steps we will eventually rid ourselves of
struct_mutex recursion!)

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_drv.h           |  2 +-
 drivers/gpu/drm/i915/i915_gem_gtt.c       | 10 ++++++++++
 drivers/gpu/drm/i915/i915_gem_gtt.h       |  2 ++
 drivers/gpu/drm/i915/i915_gem_shrinker.c  | 12 ++++++++++++
 drivers/gpu/drm/i915/selftests/mock_gtt.c |  3 +++
 5 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 13eed0f0ae81..a0e6b1dfbd28 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -3318,7 +3318,7 @@ unsigned long i915_gem_shrink(struct drm_i915_private *i915,
 unsigned long i915_gem_shrink_all(struct drm_i915_private *i915);
 void i915_gem_shrinker_register(struct drm_i915_private *i915);
 void i915_gem_shrinker_unregister(struct drm_i915_private *i915);
-
+void i915_gem_shrinker_taints_mutex(struct mutex *mutex);
 
 /* i915_gem_tiling.c */
 static inline bool i915_gem_object_needs_bit17_swizzle(struct drm_i915_gem_object *obj)
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 6d4f40e1762f..db579cdefa18 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -2116,6 +2116,7 @@ static void i915_address_space_init(struct i915_address_space *vm,
 				    struct drm_i915_private *dev_priv,
 				    const char *name)
 {
+	mutex_init(&vm->mutex);
 	drm_mm_init(&vm->mm, 0, vm->total);
 	vm->mm.head_node.color = I915_COLOR_UNEVICTABLE;
 
@@ -2124,6 +2125,13 @@ static void i915_address_space_init(struct i915_address_space *vm,
 
 	list_add_tail(&vm->global_link, &dev_priv->vm_list);
 	pagevec_init(&vm->free_pages);
+
+	/*
+	 * The vm->mutex must be reclaim safe (for use in the shrinker).
+	 * Do a dummy acquire now under fs_reclaim so that any allocation
+	 * attempt holding the lock is immediately reported by lockdep.
+	 */
+	i915_gem_shrinker_taints_mutex(&vm->mutex);
 }
 
 static void i915_address_space_fini(struct i915_address_space *vm)
@@ -2133,6 +2141,8 @@ static void i915_address_space_fini(struct i915_address_space *vm)
 
 	drm_mm_takedown(&vm->mm);
 	list_del(&vm->global_link);
+
+	mutex_destroy(&vm->mutex);
 }
 
 static void gtt_write_workarounds(struct drm_i915_private *dev_priv)
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.h b/drivers/gpu/drm/i915/i915_gem_gtt.h
index 0366b36773b1..9281c582f1d5 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.h
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.h
@@ -289,6 +289,8 @@ struct i915_address_space {
 
 	bool closed;
 
+	struct mutex mutex; /* protects vma and our lists */
+
 	struct i915_page_dma scratch_page;
 	struct i915_page_table *scratch_pt;
 	struct i915_page_directory *scratch_pd;
diff --git a/drivers/gpu/drm/i915/i915_gem_shrinker.c b/drivers/gpu/drm/i915/i915_gem_shrinker.c
index ba8885f3f428..52c061b728ca 100644
--- a/drivers/gpu/drm/i915/i915_gem_shrinker.c
+++ b/drivers/gpu/drm/i915/i915_gem_shrinker.c
@@ -23,6 +23,7 @@
  */
 
 #include <linux/oom.h>
+#include <linux/sched/mm.h>
 #include <linux/shmem_fs.h>
 #include <linux/slab.h>
 #include <linux/swap.h>
@@ -530,3 +531,14 @@ void i915_gem_shrinker_unregister(struct drm_i915_private *i915)
 	WARN_ON(unregister_oom_notifier(&i915->mm.oom_notifier));
 	unregister_shrinker(&i915->mm.shrinker);
 }
+
+void i915_gem_shrinker_taints_mutex(struct mutex *mutex)
+{
+	if (!IS_ENABLED(CONFIG_LOCKDEP))
+		return;
+
+	fs_reclaim_acquire(GFP_KERNEL);
+	mutex_lock(mutex);
+	mutex_unlock(mutex);
+	fs_reclaim_release(GFP_KERNEL);
+}
diff --git a/drivers/gpu/drm/i915/selftests/mock_gtt.c b/drivers/gpu/drm/i915/selftests/mock_gtt.c
index 57ef5f65bf3b..d6a07721d51b 100644
--- a/drivers/gpu/drm/i915/selftests/mock_gtt.c
+++ b/drivers/gpu/drm/i915/selftests/mock_gtt.c
@@ -68,6 +68,7 @@ mock_ppgtt(struct drm_i915_private *i915,
 	kref_init(&ppgtt->ref);
 	ppgtt->open_count = 1;
 
+	mutex_init(&ppgtt->vm.mutex);
 	ppgtt->vm.i915 = i915;
 	ppgtt->vm.total = round_down(U64_MAX, PAGE_SIZE);
 	ppgtt->vm.file = ERR_PTR(-ENODEV);
@@ -109,6 +110,7 @@ void mock_init_ggtt(struct drm_i915_private *i915)
 
 	INIT_LIST_HEAD(&i915->vm_list);
 
+	mutex_init(&ggtt->vm.mutex);
 	ggtt->vm.i915 = i915;
 
 	ggtt->gmadr = (struct resource) DEFINE_RES_MEM(0, 2048 * PAGE_SIZE);
@@ -133,4 +135,5 @@ void mock_fini_ggtt(struct drm_i915_private *i915)
 	struct i915_ggtt *ggtt = &i915->ggtt;
 
 	i915_address_space_fini(&ggtt->vm);
+	mutex_destroy(&ggtt->vm.mutex);
 }
-- 
2.18.0



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