linux-kernel - [PATCH 2/6] drm/ttm: use new ww_mutex_(un)lock_for

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Date:   Fri, 14 Jun 2019 14:41:21 +0200
From:   "Christian König" 
        <ckoenig.leichtzumerken@...il.com>
To:     daniel@...ll.ch, l.stach@...gutronix.de,
        linux+etnaviv@...linux.org.uk, christian.gmeiner@...il.com,
        yuq825@...il.com, eric@...olt.net, peterz@...radead.org,
        thellstrom@...are.com, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, etnaviv@...ts.freedesktop.org,
        lima@...ts.freedesktop.org
Subject: [PATCH 2/6] drm/ttm: use new ww_mutex_(un)lock_for_each macros

Use the provided macros instead of implementing deadlock handling on our own.

Signed-off-by: Christian König <christian.koenig@....com>
---
 drivers/gpu/drm/ttm/ttm_execbuf_util.c | 87 +++++++++-----------------
 1 file changed, 30 insertions(+), 57 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_execbuf_util.c b/drivers/gpu/drm/ttm/ttm_execbuf_util.c
index 957ec375a4ba..3c3ac6c94d7f 100644
--- a/drivers/gpu/drm/ttm/ttm_execbuf_util.c
+++ b/drivers/gpu/drm/ttm/ttm_execbuf_util.c
@@ -33,16 +33,6 @@
 #include <linux/sched.h>
 #include <linux/module.h>
 
-static void ttm_eu_backoff_reservation_reverse(struct list_head *list,
-					      struct ttm_validate_buffer *entry)
-{
-	list_for_each_entry_continue_reverse(entry, list, head) {
-		struct ttm_buffer_object *bo = entry->bo;
-
-		reservation_object_unlock(bo->resv);
-	}
-}
-
 static void ttm_eu_del_from_lru_locked(struct list_head *list)
 {
 	struct ttm_validate_buffer *entry;
@@ -96,8 +86,9 @@ int ttm_eu_reserve_buffers(struct ww_acquire_ctx *ticket,
 			   struct list_head *list, bool intr,
 			   struct list_head *dups, bool del_lru)
 {
-	struct ttm_bo_global *glob;
 	struct ttm_validate_buffer *entry;
+	struct ww_mutex *contended;
+	struct ttm_bo_global *glob;
 	int ret;
 
 	if (list_empty(list))
@@ -109,68 +100,39 @@ int ttm_eu_reserve_buffers(struct ww_acquire_ctx *ticket,
 	if (ticket)
 		ww_acquire_init(ticket, &reservation_ww_class);
 
-	list_for_each_entry(entry, list, head) {
+	ww_mutex_lock_for_each(list_for_each_entry(entry, list, head),
+			       &entry->bo->resv->lock, contended, ret,
+			       intr, ticket)
+	{
 		struct ttm_buffer_object *bo = entry->bo;
 
-		ret = __ttm_bo_reserve(bo, intr, (ticket == NULL), ticket);
 		if (!ret && unlikely(atomic_read(&bo->cpu_writers) > 0)) {
 			reservation_object_unlock(bo->resv);
-
 			ret = -EBUSY;
+			goto error;
+		}
 
-		} else if (ret == -EALREADY && dups) {
+		if (ret == -EALREADY && dups) {
 			struct ttm_validate_buffer *safe = entry;
+
 			entry = list_prev_entry(entry, head);
 			list_del(&safe->head);
 			list_add(&safe->head, dups);
 			continue;
 		}
 
-		if (!ret) {
-			if (!entry->num_shared)
-				continue;
-
-			ret = reservation_object_reserve_shared(bo->resv,
-								entry->num_shared);
-			if (!ret)
-				continue;
-		}
+		if (unlikely(ret))
+			goto error;
 
-		/* uh oh, we lost out, drop every reservation and try
-		 * to only reserve this buffer, then start over if
-		 * this succeeds.
-		 */
-		ttm_eu_backoff_reservation_reverse(list, entry);
-
-		if (ret == -EDEADLK) {
-			if (intr) {
-				ret = ww_mutex_lock_slow_interruptible(&bo->resv->lock,
-								       ticket);
-			} else {
-				ww_mutex_lock_slow(&bo->resv->lock, ticket);
-				ret = 0;
-			}
-		}
+		if (!entry->num_shared)
+			continue;
 
-		if (!ret && entry->num_shared)
-			ret = reservation_object_reserve_shared(bo->resv,
-								entry->num_shared);
-
-		if (unlikely(ret != 0)) {
-			if (ret == -EINTR)
-				ret = -ERESTARTSYS;
-			if (ticket) {
-				ww_acquire_done(ticket);
-				ww_acquire_fini(ticket);
-			}
-			return ret;
+		ret = reservation_object_reserve_shared(bo->resv,
+							entry->num_shared);
+		if (unlikely(ret)) {
+			reservation_object_unlock(bo->resv);
+			goto error;
 		}
-
-		/* move this item to the front of the list,
-		 * forces correct iteration of the loop without keeping track
-		 */
-		list_del(&entry->head);
-		list_add(&entry->head, list);
 	}
 
 	if (del_lru) {
@@ -179,6 +141,17 @@ int ttm_eu_reserve_buffers(struct ww_acquire_ctx *ticket,
 		spin_unlock(&glob->lru_lock);
 	}
 	return 0;
+
+error:
+	ww_mutex_unlock_for_each(list_for_each_entry(entry, list, head),
+				 &entry->bo->resv->lock, contended);
+	if (ret == -EINTR)
+		ret = -ERESTARTSYS;
+	if (ticket) {
+		ww_acquire_done(ticket);
+		ww_acquire_fini(ticket);
+	}
+	return ret;
 }
 EXPORT_SYMBOL(ttm_eu_reserve_buffers);
 
-- 
2.17.1