[11/20] drm/i915/gem: Separate the ww_mutex walker into its own list
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Message ID 20200706061926.6687-12-chris@chris-wilson.co.uk
State New
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Series
  • [01/20] drm/i915: Preallocate stashes for vma page-directories
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Commit Message

Chris Wilson July 6, 2020, 6:19 a.m. UTC
In preparation for making eb_vma bigger and heavy to run inn parallel,
we need to stop apply an in-place swap() to reorder around ww_mutex
deadlocks. Keep the array intact and reorder the locks using a dedicated
list.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
 .../gpu/drm/i915/gem/i915_gem_execbuffer.c    | 83 ++++++++++++-------
 1 file changed, 54 insertions(+), 29 deletions(-)

Comments

Tvrtko Ursulin July 13, 2020, 2:53 p.m. UTC | #1
On 06/07/2020 07:19, Chris Wilson wrote:
> In preparation for making eb_vma bigger and heavy to run inn parallel,

in

> we need to stop apply an in-place swap() to reorder around ww_mutex

applying

> deadlocks. Keep the array intact and reorder the locks using a dedicated
> list.
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
>   .../gpu/drm/i915/gem/i915_gem_execbuffer.c    | 83 ++++++++++++-------
>   1 file changed, 54 insertions(+), 29 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> index 6d20be29ff3c..4d8ac89c56fc 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> @@ -37,6 +37,7 @@ struct eb_vma {
>   	struct list_head bind_link;
>   	struct list_head unbound_link;
>   	struct list_head reloc_link;
> +	struct list_head submit_link;
>   
>   	struct hlist_node node;
>   	u32 handle;
> @@ -248,6 +249,8 @@ struct i915_execbuffer {
>   	/** list of vma that have execobj.relocation_count */
>   	struct list_head relocs;
>   
> +	struct list_head submit_list;
> +
>   	/**
>   	 * Track the most recently used object for relocations, as we
>   	 * frequently have to perform multiple relocations within the same
> @@ -341,6 +344,42 @@ static void eb_vma_array_put(struct eb_vma_array *arr)
>   	kref_put(&arr->kref, eb_vma_array_destroy);
>   }
>   
> +static int
> +eb_lock_vma(struct i915_execbuffer *eb, struct ww_acquire_ctx *acquire)

vmas plural?

> +{
> +	struct eb_vma *ev;
> +	int err = 0;
> +
> +	list_for_each_entry(ev, &eb->submit_list, submit_link) {
> +		struct i915_vma *vma = ev->vma;
> +
> +		err = ww_mutex_lock_interruptible(&vma->resv->lock, acquire);
> +		if (err == -EDEADLK) {
> +			struct eb_vma *unlock = ev, *en;
> +
> +			list_for_each_entry_safe_continue_reverse(unlock, en,
> +								  &eb->submit_list,
> +								  submit_link) {
> +				ww_mutex_unlock(&unlock->vma->resv->lock);
> +				list_move_tail(&unlock->submit_link, &eb->submit_list);
> +			}
> +
> +			GEM_BUG_ON(!list_is_first(&ev->submit_link, &eb->submit_list));
> +			err = ww_mutex_lock_slow_interruptible(&vma->resv->lock,
> +							       acquire);
> +		}
> +		if (err) {
> +			list_for_each_entry_continue_reverse(ev,
> +							     &eb->submit_list,
> +							     submit_link)
> +				ww_mutex_unlock(&ev->vma->resv->lock);
> +			break;
> +		}
> +	}
> +
> +	return err;
> +}
> +
>   static int eb_create(struct i915_execbuffer *eb)
>   {
>   	/* Allocate an extra slot for use by the command parser + sentinel */
> @@ -393,6 +432,10 @@ static int eb_create(struct i915_execbuffer *eb)
>   		eb->lut_size = -eb->buffer_count;
>   	}
>   
> +	INIT_LIST_HEAD(&eb->bind_list);
> +	INIT_LIST_HEAD(&eb->submit_list);
> +	INIT_LIST_HEAD(&eb->relocs);
> +
>   	return 0;
>   }
>   
> @@ -574,6 +617,7 @@ eb_add_vma(struct i915_execbuffer *eb,
>   	}
>   
>   	list_add_tail(&ev->bind_link, &eb->bind_list);
> +	list_add_tail(&ev->submit_link, &eb->submit_list);
>   
>   	if (entry->relocation_count)
>   		list_add_tail(&ev->reloc_link, &eb->relocs);
> @@ -910,9 +954,6 @@ static int eb_lookup_vmas(struct i915_execbuffer *eb)
>   	unsigned int i;
>   	int err = 0;
>   
> -	INIT_LIST_HEAD(&eb->bind_list);
> -	INIT_LIST_HEAD(&eb->relocs);
> -
>   	for (i = 0; i < eb->buffer_count; i++) {
>   		struct i915_vma *vma;
>   
> @@ -1583,38 +1624,19 @@ static int eb_relocate(struct i915_execbuffer *eb)
>   
>   static int eb_move_to_gpu(struct i915_execbuffer *eb)
>   {
> -	const unsigned int count = eb->buffer_count;
>   	struct ww_acquire_ctx acquire;
> -	unsigned int i;
> +	struct eb_vma *ev;
>   	int err = 0;
>   
>   	ww_acquire_init(&acquire, &reservation_ww_class);
>   
> -	for (i = 0; i < count; i++) {
> -		struct eb_vma *ev = &eb->vma[i];
> -		struct i915_vma *vma = ev->vma;
> -
> -		err = ww_mutex_lock_interruptible(&vma->resv->lock, &acquire);
> -		if (err == -EDEADLK) {
> -			GEM_BUG_ON(i == 0);
> -			do {
> -				int j = i - 1;
> -
> -				ww_mutex_unlock(&eb->vma[j].vma->resv->lock);
> -
> -				swap(eb->vma[i],  eb->vma[j]);
> -			} while (--i);
> +	err = eb_lock_vma(eb, &acquire);
> +	if (err)
> +		goto err_fini;
>   
> -			err = ww_mutex_lock_slow_interruptible(&vma->resv->lock,
> -							       &acquire);
> -		}
> -		if (err)
> -			break;
> -	}
>   	ww_acquire_done(&acquire);
>   
> -	while (i--) {
> -		struct eb_vma *ev = &eb->vma[i];
> +	list_for_each_entry(ev, &eb->submit_list, submit_link) {
>   		struct i915_vma *vma = ev->vma;
>   		unsigned int flags = ev->flags;
>   		struct drm_i915_gem_object *obj = vma->obj;
> @@ -1671,6 +1693,8 @@ static int eb_move_to_gpu(struct i915_execbuffer *eb)
>   	intel_gt_chipset_flush(eb->engine->gt);
>   	return 0;
>   
> +err_fini:
> +	ww_acquire_fini(&acquire);
>   err_skip:
>   	i915_request_set_error_once(eb->request, err);
>   	return err;
> @@ -1952,9 +1976,10 @@ static int eb_parse(struct i915_execbuffer *eb)
>   	if (err)
>   		goto err_trampoline;
>   
> -	eb->vma[eb->buffer_count].vma = i915_vma_get(shadow);
> -	eb->vma[eb->buffer_count].flags = __EXEC_OBJECT_HAS_PIN;
>   	eb->batch = &eb->vma[eb->buffer_count++];
> +	eb->batch->vma = i915_vma_get(shadow);
> +	eb->batch->flags = __EXEC_OBJECT_HAS_PIN;
> +	list_add_tail(&eb->batch->submit_link, &eb->submit_list);
>   	eb->vma[eb->buffer_count].vma = NULL;
>   
>   	eb->trampoline = trampoline;
> 

Just a temporary stage... are we reviewing those? Best if they can be 
avoided.

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Regards,

Tvrtko
Chris Wilson July 14, 2020, 2:10 p.m. UTC | #2
Quoting Tvrtko Ursulin (2020-07-13 15:53:56)
> 
> On 06/07/2020 07:19, Chris Wilson wrote:
> Just a temporary stage... are we reviewing those? Best if they can be 
> avoided.

Yes, I am not chuffed in having it. But with the transition from using
an array of execobj[] to having a list that includes the supplementary
objects, the inplace swap() now breaks the lists. We would have to do a
bunch of list_replace() to preserve them. At the moment, I think this is
the lessor of evils, although it is quite hideous.
-Chris

Patch
diff mbox series

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
index 6d20be29ff3c..4d8ac89c56fc 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
@@ -37,6 +37,7 @@  struct eb_vma {
 	struct list_head bind_link;
 	struct list_head unbound_link;
 	struct list_head reloc_link;
+	struct list_head submit_link;
 
 	struct hlist_node node;
 	u32 handle;
@@ -248,6 +249,8 @@  struct i915_execbuffer {
 	/** list of vma that have execobj.relocation_count */
 	struct list_head relocs;
 
+	struct list_head submit_list;
+
 	/**
 	 * Track the most recently used object for relocations, as we
 	 * frequently have to perform multiple relocations within the same
@@ -341,6 +344,42 @@  static void eb_vma_array_put(struct eb_vma_array *arr)
 	kref_put(&arr->kref, eb_vma_array_destroy);
 }
 
+static int
+eb_lock_vma(struct i915_execbuffer *eb, struct ww_acquire_ctx *acquire)
+{
+	struct eb_vma *ev;
+	int err = 0;
+
+	list_for_each_entry(ev, &eb->submit_list, submit_link) {
+		struct i915_vma *vma = ev->vma;
+
+		err = ww_mutex_lock_interruptible(&vma->resv->lock, acquire);
+		if (err == -EDEADLK) {
+			struct eb_vma *unlock = ev, *en;
+
+			list_for_each_entry_safe_continue_reverse(unlock, en,
+								  &eb->submit_list,
+								  submit_link) {
+				ww_mutex_unlock(&unlock->vma->resv->lock);
+				list_move_tail(&unlock->submit_link, &eb->submit_list);
+			}
+
+			GEM_BUG_ON(!list_is_first(&ev->submit_link, &eb->submit_list));
+			err = ww_mutex_lock_slow_interruptible(&vma->resv->lock,
+							       acquire);
+		}
+		if (err) {
+			list_for_each_entry_continue_reverse(ev,
+							     &eb->submit_list,
+							     submit_link)
+				ww_mutex_unlock(&ev->vma->resv->lock);
+			break;
+		}
+	}
+
+	return err;
+}
+
 static int eb_create(struct i915_execbuffer *eb)
 {
 	/* Allocate an extra slot for use by the command parser + sentinel */
@@ -393,6 +432,10 @@  static int eb_create(struct i915_execbuffer *eb)
 		eb->lut_size = -eb->buffer_count;
 	}
 
+	INIT_LIST_HEAD(&eb->bind_list);
+	INIT_LIST_HEAD(&eb->submit_list);
+	INIT_LIST_HEAD(&eb->relocs);
+
 	return 0;
 }
 
@@ -574,6 +617,7 @@  eb_add_vma(struct i915_execbuffer *eb,
 	}
 
 	list_add_tail(&ev->bind_link, &eb->bind_list);
+	list_add_tail(&ev->submit_link, &eb->submit_list);
 
 	if (entry->relocation_count)
 		list_add_tail(&ev->reloc_link, &eb->relocs);
@@ -910,9 +954,6 @@  static int eb_lookup_vmas(struct i915_execbuffer *eb)
 	unsigned int i;
 	int err = 0;
 
-	INIT_LIST_HEAD(&eb->bind_list);
-	INIT_LIST_HEAD(&eb->relocs);
-
 	for (i = 0; i < eb->buffer_count; i++) {
 		struct i915_vma *vma;
 
@@ -1583,38 +1624,19 @@  static int eb_relocate(struct i915_execbuffer *eb)
 
 static int eb_move_to_gpu(struct i915_execbuffer *eb)
 {
-	const unsigned int count = eb->buffer_count;
 	struct ww_acquire_ctx acquire;
-	unsigned int i;
+	struct eb_vma *ev;
 	int err = 0;
 
 	ww_acquire_init(&acquire, &reservation_ww_class);
 
-	for (i = 0; i < count; i++) {
-		struct eb_vma *ev = &eb->vma[i];
-		struct i915_vma *vma = ev->vma;
-
-		err = ww_mutex_lock_interruptible(&vma->resv->lock, &acquire);
-		if (err == -EDEADLK) {
-			GEM_BUG_ON(i == 0);
-			do {
-				int j = i - 1;
-
-				ww_mutex_unlock(&eb->vma[j].vma->resv->lock);
-
-				swap(eb->vma[i],  eb->vma[j]);
-			} while (--i);
+	err = eb_lock_vma(eb, &acquire);
+	if (err)
+		goto err_fini;
 
-			err = ww_mutex_lock_slow_interruptible(&vma->resv->lock,
-							       &acquire);
-		}
-		if (err)
-			break;
-	}
 	ww_acquire_done(&acquire);
 
-	while (i--) {
-		struct eb_vma *ev = &eb->vma[i];
+	list_for_each_entry(ev, &eb->submit_list, submit_link) {
 		struct i915_vma *vma = ev->vma;
 		unsigned int flags = ev->flags;
 		struct drm_i915_gem_object *obj = vma->obj;
@@ -1671,6 +1693,8 @@  static int eb_move_to_gpu(struct i915_execbuffer *eb)
 	intel_gt_chipset_flush(eb->engine->gt);
 	return 0;
 
+err_fini:
+	ww_acquire_fini(&acquire);
 err_skip:
 	i915_request_set_error_once(eb->request, err);
 	return err;
@@ -1952,9 +1976,10 @@  static int eb_parse(struct i915_execbuffer *eb)
 	if (err)
 		goto err_trampoline;
 
-	eb->vma[eb->buffer_count].vma = i915_vma_get(shadow);
-	eb->vma[eb->buffer_count].flags = __EXEC_OBJECT_HAS_PIN;
 	eb->batch = &eb->vma[eb->buffer_count++];
+	eb->batch->vma = i915_vma_get(shadow);
+	eb->batch->flags = __EXEC_OBJECT_HAS_PIN;
+	list_add_tail(&eb->batch->submit_link, &eb->submit_list);
 	eb->vma[eb->buffer_count].vma = NULL;
 
 	eb->trampoline = trampoline;