On 7/3/2026 6:41 PM, Thomas Hellström wrote:
On Fri, 2026-07-03 at 15:08 +0200, Christian König wrote:
Arun please take a look at this.
Thanks,
Christian.
FWIW Sashiko claims there is yet another pre-existing bug WRT ordering
here, but since the fix wasn't needed for the rest of the series, I
focused on this one.
Thanks for pointing that out. I have sent a fix for the pre-existing bug
reported by Sashiko as a separate patch.
https://patchwork.freedesktop.org/patch/741782/
Thanks,
Arun.
Thanks,
Thomas
On 7/3/26 15:05, Thomas Hellström wrote:
drmm_cgroup_register_region() is called before INIT_LIST_HEAD() and
gpu_buddy_init() in amdgpu_vram_mgr_init(). If it fails, the
function
returns early and bypasses those initializations.
Since adev->mman.initialized is set to true before
amdgpu_vram_mgr_init()
is called, a failure triggers amdgpu_ttm_fini(), which calls
amdgpu_vram_mgr_fini(), which then:
- Calls list_for_each_entry_safe() on reservations_pending and
reserved_pages, whose list_head::next pointers are zero-
initialized
(NULL). The loop does not recognize them as empty and
dereferences NULL.
- Calls gpu_buddy_fini(), which iterates free_trees[]
unconditionally
via for_each_free_tree(). Since mm->free_trees is NULL
(never allocated), this dereferences NULL.
Both result in a kernel panic on the module load error path.
Fix by moving drmm_cgroup_register_region() to after the list and
buddy
allocator are fully initialized, so the teardown path is safe to
run.
Reported-by: Sashiko-bot <[email protected]>
Closes:
https://sashiko.dev/#/patchset/[email protected]?part=4
Fixes: 2b624a2c1865 ("drm/ttm: Handle cgroup based eviction in
TTM")
Cc: Friedrich Vock <[email protected]>
Cc: Maarten Lankhorst <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Maxime Ripard <[email protected]>
Cc: Christian König <[email protected]>
Cc: Alex Deucher <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: <[email protected]> # v6.14+
Assisted-by: GitHub_Copilot:claude-sonnet-4.6
Signed-off-by: Thomas Hellström <[email protected]>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
index 2a241a5b12c4..ac3f71d77140 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
@@ -918,9 +918,6 @@ int amdgpu_vram_mgr_init(struct amdgpu_device
*adev)
struct ttm_resource_manager *man = &mgr->manager;
int err;
- man->cg = drmm_cgroup_register_region(adev_to_drm(adev),
"vram", adev->gmc.real_vram_size);
- if (IS_ERR(man->cg))
- return PTR_ERR(man->cg);
ttm_resource_manager_init(man, &adev->mman.bdev,
adev->gmc.real_vram_size);
@@ -935,6 +932,10 @@ int amdgpu_vram_mgr_init(struct amdgpu_device
*adev)
if (err)
return err;
+ man->cg = drmm_cgroup_register_region(adev_to_drm(adev),
"vram", adev->gmc.real_vram_size);
+ if (IS_ERR(man->cg))
+ return PTR_ERR(man->cg);
+
ttm_set_driver_manager(&adev->mman.bdev, TTM_PL_VRAM,
&mgr->manager);
ttm_resource_manager_set_used(man, true);
return 0;
