[Intel-gfx] [CI] drm/i915: Check current i915_vma.pin_count status first on unbind

[Chris Wilson]

Do an early rejection of a i915_vma_unbind() attempt if the i915_vma is
currently pinned, without waiting to see if the inflight operations may
unpin it. We see this problem with the shrinker trying to unbind the
active vma from inside its bind worker:

<6> [472.618968] Workqueue: events_unbound fence_work [i915]
<4> [472.618970] Call Trace:
<4> [472.618974]  ? __schedule+0x2e5/0x810
<4> [472.618978]  schedule+0x37/0xe0
<4> [472.618982]  schedule_preempt_disabled+0xf/0x20
<4> [472.618984]  __mutex_lock+0x281/0x9c0
<4> [472.618987]  ? mark_held_locks+0x49/0x70
<4> [472.618989]  ? _raw_spin_unlock_irqrestore+0x47/0x60
<4> [472.619038]  ? i915_vma_unbind+0xae/0x110 [i915]
<4> [472.619084]  ? i915_vma_unbind+0xae/0x110 [i915]
<4> [472.619122]  i915_vma_unbind+0xae/0x110 [i915]
<4> [472.619165]  i915_gem_object_unbind+0x1dc/0x400 [i915]
<4> [472.619208]  i915_gem_shrink+0x328/0x660 [i915]
<4> [472.619250]  ? i915_gem_shrink_all+0x38/0x60 [i915]
<4> [472.619282]  i915_gem_shrink_all+0x38/0x60 [i915]
<4> [472.619325]  vm_alloc_page.constprop.25+0x1aa/0x240 [i915]
<4> [472.619330]  ? rcu_read_lock_sched_held+0x4d/0x80
<4> [472.619363]  ? __alloc_pd+0xb/0x30 [i915]
<4> [472.619366]  ? module_assert_mutex_or_preempt+0xf/0x30
<4> [472.619368]  ? __module_address+0x23/0xe0
<4> [472.619371]  ? is_module_address+0x26/0x40
<4> [472.619374]  ? static_obj+0x34/0x50
<4> [472.619376]  ? lockdep_init_map+0x4d/0x1e0
<4> [472.619407]  setup_page_dma+0xd/0x90 [i915]
<4> [472.619437]  alloc_pd+0x29/0x50 [i915]
<4> [472.619470]  __gen8_ppgtt_alloc+0x443/0x6b0 [i915]
<4> [472.619503]  gen8_ppgtt_alloc+0xd7/0x300 [i915]
<4> [472.619535]  ppgtt_bind_vma+0x2a/0xe0 [i915]
<4> [472.619577]  __vma_bind+0x26/0x40 [i915]
<4> [472.619611]  fence_work+0x1c/0x90 [i915]
<4> [472.619617]  process_one_work+0x26a/0x620

Fixes: 2850748ef876 ("drm/i915: Pull i915_vma_pin under the vm->mutex")
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
---
 drivers/gpu/drm/i915/i915_vma.c | 21 +++++++++------------
 1 file changed, 9 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index 84e03da0d5f9..24dd912fdd6b 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -317,6 +317,8 @@ static void __vma_release(struct dma_fence_work *work)
 
 	if (vw->pinned)
 		__i915_gem_object_unpin_pages(vw->pinned);
+	if (vw->vma)
+		i915_vma_unpin(vw->vma);
 }
 
 static const struct dma_fence_work_ops bind_ops = {
@@ -407,6 +409,7 @@ int i915_vma_bind(struct i915_vma *vma,
 			__i915_gem_object_pin_pages(vma->obj);
 			work->pinned = vma->obj;
 		}
+		__i915_vma_pin(vma);
 	} else {
 		GEM_BUG_ON((bind_flags & ~vma_flags) & vma->vm->bind_async_flags);
 		ret = vma->ops->bind_vma(vma, cache_level, bind_flags);
@@ -1033,6 +1036,7 @@ void i915_vma_release(struct kref *ref)
 	struct i915_vma *vma = container_of(ref, typeof(*vma), ref);
 
 	if (drm_mm_node_allocated(&vma->node)) {
+		WARN_ON(i915_vma_sync(vma));
 		mutex_lock(&vma->vm->mutex);
 		atomic_and(~I915_VMA_PIN_MASK, &vma->flags);
 		WARN_ON(__i915_vma_unbind(vma));
@@ -1190,18 +1194,6 @@ int __i915_vma_unbind(struct i915_vma *vma)
 
 	lockdep_assert_held(&vma->vm->mutex);
 
-	/*
-	 * First wait upon any activity as retiring the request may
-	 * have side-effects such as unpinning or even unbinding this vma.
-	 *
-	 * XXX Actually waiting under the vm->mutex is a hinderance and
-	 * should be pipelined wherever possible. In cases where that is
-	 * unavoidable, we should lift the wait to before the mutex.
-	 */
-	ret = i915_vma_sync(vma);
-	if (ret)
-		return ret;
-
 	if (i915_vma_is_pinned(vma)) {
 		vma_print_allocator(vma, "is pinned");
 		return -EAGAIN;
@@ -1275,6 +1267,11 @@ int i915_vma_unbind(struct i915_vma *vma)
 	if (!drm_mm_node_allocated(&vma->node))
 		return 0;
 
+	if (i915_vma_is_pinned(vma)) {
+		vma_print_allocator(vma, "is pinned");
+		return -EAGAIN;
+	}
+
 	if (i915_vma_is_bound(vma, I915_VMA_GLOBAL_BIND))
 		/* XXX not always required: nop_clear_range */
 		wakeref = intel_runtime_pm_get(&vm->i915->runtime_pm);
-- 
2.25.0