drm: mm always protect change to unused_nodes with unused_lock spinlock (a698cf34) · Commits · 戴 / test

unused_nodes modification needs to be protected by unused_lock spinlock. Here is an example of an usage where there is no such protection without this patch. Process 1: 1-drm_mm_pre_get(this function modify unused_nodes list) 2-spin_lock(spinlock protecting mm struct) 3-drm_mm_put_block(this function might modify unused_nodes list but doesn't protect modification with unused_lock) 4-spin_unlock(spinlock protecting mm struct) Process2: 1-drm_mm_pre_get(this function modify unused_nodes list) At this point Process1 & Process2 might both be doing modification to unused_nodes list. This patch add unused_lock protection into drm_mm_put_block to avoid such issue. Signed-off-by:

Jerome Glisse <jglisse@redhat.com> Signed-off-by:

Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_mm.c

+9 −0

Original line number	Diff line number	Diff line
		@@ -103,6 +103,11 @@ static struct drm_mm_node drm_mm_kmalloc(struct drm_mm mm, int atomic)
		return child;
		}

		/* drm_mm_pre_get() - pre allocate drm_mm_node structure
		* drm_mm: memory manager struct we are pre-allocating for
		*
		* Returns 0 on success or -ENOMEM if allocation fails.
		*/
		int drm_mm_pre_get(struct drm_mm *mm)
		{
		struct drm_mm_node *node;
		@@ -253,12 +258,14 @@ void drm_mm_put_block(struct drm_mm_node *cur)
		prev_node->size += next_node->size;
		list_del(&next_node->ml_entry);
		list_del(&next_node->fl_entry);
		spin_lock(&mm->unused_lock);
		if (mm->num_unused < MM_UNUSED_TARGET) {
		list_add(&next_node->fl_entry,
		&mm->unused_nodes);
		++mm->num_unused;
		} else
		kfree(next_node);
		spin_unlock(&mm->unused_lock);
		} else {
		next_node->size += cur->size;
		next_node->start = cur->start;
		@@ -271,11 +278,13 @@ void drm_mm_put_block(struct drm_mm_node *cur)
		list_add(&cur->fl_entry, &mm->fl_entry);
		} else {
		list_del(&cur->ml_entry);
		spin_lock(&mm->unused_lock);
		if (mm->num_unused < MM_UNUSED_TARGET) {
		list_add(&cur->fl_entry, &mm->unused_nodes);
		++mm->num_unused;
		} else
		kfree(cur);
		spin_unlock(&mm->unused_lock);
		}
		}

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