[Intel-gfx] [PATCH v6 01/15] drm/i915: Untangle the vma pages_mutex

Thomas Hellström
2021-05-28T10:58:00Z

Any sleeping dma_resv lock taken while the vma pages_mutex is held
will cause a lockdep splat.
Move the i915_gem_object_pin_pages() call out of the pages_mutex
critical section.

Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
---
drivers/gpu/drm/i915/i915_vma.c | 29 +++++++++++++++++------------
1 file changed, 17 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index b319fd3f91cc..0f227f28b280 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -800,32 +800,37 @@ static bool try_qad_pin(struct i915_vma *vma, unsigned int flags)
static int vma_get_pages(struct i915_vma *vma)
{
int err = 0;
+ bool pinned_pages = false;

if (atomic_add_unless(&vma->pages_count, 1, 0))
return 0;

+ if (vma->obj) {
+ err = i915_gem_object_pin_pages(vma->obj);
+ if (err)
+ return err;
+ pinned_pages = true;
+ }
+
/* Allocations ahoy! */
- if (mutex_lock_interruptible(&vma->pages_mutex))
- return -EINTR;
+ if (mutex_lock_interruptible(&vma->pages_mutex)) {
+ err = -EINTR;
+ goto unpin;
+ }

if (!atomic_read(&vma->pages_count)) {
- if (vma->obj) {
- err = i915_gem_object_pin_pages(vma->obj);
- if (err)
- goto unlock;
- }
-
err = vma->ops->set_pages(vma);
- if (err) {
- if (vma->obj)
- i915_gem_object_unpin_pages(vma->obj);
+ if (err)
goto unlock;
- }
+ pinned_pages = false;
}
atomic_inc(&vma->pages_count);

unlock:
mutex_unlock(&vma->pages_mutex);
+unpin:
+ if (pinned_pages)
+ __i915_gem_object_unpin_pages(vma->obj);

return err;