[Intel-gfx] [PATCH v8 34/69] drm/i915: Add ww locking around vm_access()

[Maarten Lankhorst]

i915_gem_object_pin_map potentially needs a ww context, so ensure we
have one we can revoke.

Signed-off-by: Maarten Lankhorst <maarten.lankho...@linux.intel.com>
Reviewed-by: Thomas Hellström <thomas.hellst...@linux.intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_mman.c | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c 
b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
index 163208a6260d..2561a2f1e54f 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
@@ -421,7 +421,9 @@ vm_access(struct vm_area_struct *area, unsigned long addr,
 {
        struct i915_mmap_offset *mmo = area->vm_private_data;
        struct drm_i915_gem_object *obj = mmo->obj;
+       struct i915_gem_ww_ctx ww;
        void *vaddr;
+       int err = 0;
 
        if (i915_gem_object_is_readonly(obj) && write)
                return -EACCES;
@@ -430,10 +432,18 @@ vm_access(struct vm_area_struct *area, unsigned long addr,
        if (addr >= obj->base.size)
                return -EINVAL;
 
+       i915_gem_ww_ctx_init(&ww, true);
+retry:
+       err = i915_gem_object_lock(obj, &ww);
+       if (err)
+               goto out;
+
        /* As this is primarily for debugging, let's focus on simplicity */
        vaddr = i915_gem_object_pin_map(obj, I915_MAP_FORCE_WC);
-       if (IS_ERR(vaddr))
-               return PTR_ERR(vaddr);
+       if (IS_ERR(vaddr)) {
+               err = PTR_ERR(vaddr);
+               goto out;
+       }
 
        if (write) {
                memcpy(vaddr + addr, buf, len);
@@ -443,6 +453,16 @@ vm_access(struct vm_area_struct *area, unsigned long addr,
        }
 
        i915_gem_object_unpin_map(obj);
+out:
+       if (err == -EDEADLK) {
+               err = i915_gem_ww_ctx_backoff(&ww);
+               if (!err)
+                       goto retry;
+       }
+       i915_gem_ww_ctx_fini(&ww);
+
+       if (err)
+               return err;
 
        return len;
 }
-- 
2.30.1

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