From fd6df983f8f126ffb788c1f77cd999288d85349c Mon Sep 17 00:00:00 2001
From: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Date: Fri, 28 Jan 2022 09:57:39 +0100
Subject: drm/i915: Allow dead vm to unbind vma's without lock.
Git-commit: a594525c82e0b8d677a7e5fd13c7c115d41e9722
Patch-mainline: v5.18-rc1
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225
i915_gem_vm_close may take the lock, and we currently have no better way
of handling this. At least for now, allow a path in which holding vm->mutex
is sufficient. This is the case, because the object destroy path will
forcefully take vm->mutex now.
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220128085739.1464568-1-maarten.lankhorst@linux.intel.com
Reviewed-by: Thomas Hellstrom <thomas.hellstrom@linux.intel.com>
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
drivers/gpu/drm/i915/i915_vma.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index e109ddd9fe17..845cd88f8313 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -40,6 +40,17 @@
#include "i915_vma.h"
#include "i915_vma_resource.h"
+static inline void assert_vma_held_evict(const struct i915_vma *vma)
+{
+ /*
+ * We may be forced to unbind when the vm is dead, to clean it up.
+ * This is the only exception to the requirement of the object lock
+ * being held.
+ */
+ if (atomic_read(&vma->vm->open))
+ assert_object_held_shared(vma->obj);
+}
+
static struct kmem_cache *slab_vmas;
static struct i915_vma *i915_vma_alloc(void)
@@ -1780,7 +1791,7 @@ struct dma_fence *__i915_vma_evict(struct i915_vma *vma, bool async)
struct dma_fence *unbind_fence;
GEM_BUG_ON(i915_vma_is_pinned(vma));
- assert_object_held_shared(vma->obj);
+ assert_vma_held_evict(vma);
if (i915_vma_is_map_and_fenceable(vma)) {
/* Force a pagefault for domain tracking on next user access */
@@ -1847,7 +1858,7 @@ int __i915_vma_unbind(struct i915_vma *vma)
int ret;
lockdep_assert_held(&vma->vm->mutex);
- assert_object_held_shared(vma->obj);
+ assert_vma_held_evict(vma);
if (!drm_mm_node_allocated(&vma->node))
return 0;
--
2.38.1