On 6/18/26 07:52, Mikhail Gavrilov wrote:
> amdgpu_lockdep_init() trains lockdep on the driver lock ordering by
> taking a chain of dummy locks in order and calling fs_reclaim_acquire()
> in the middle of it. The fs_reclaim_acquire()/fs_reclaim_release() pair
> is placed while notifier_lock (amdgpu_notifier_lock_key) is held, which
> teaches lockdep that it is legal to enter memory reclaim with the MMU
> notifier lock held:
>
> notifier_lock -> vram_lock -> reset_domain->sem -> reset_lock ->
> fs_reclaim
>
> notifier_lock is, however, acquired from the MMU notifier invalidate
> callback amdgpu_hmm_invalidate_gfx(), which mm/ runs from inside memory
> reclaim via __mmu_notifier_invalidate_range_start(). That establishes
> the mandatory reverse ordering:
>
> fs_reclaim -> mmu_notifier_invalidate_range_start -> notifier_lock
>
> The two together form a cycle. It stays dormant until reclaim first
> unmaps a page covered by an amdgpu userptr interval notifier, at which
> point kswapd closes the loop and lockdep reports a false circular
> locking dependency:
>
> WARNING: possible circular locking dependency detected
> kswapd0/268 is trying to acquire lock:
> (&amdgpu_notifier_lock_key){+.+.}, at: amdgpu_hmm_invalidate_gfx
> but task is already holding lock:
> (mmu_notifier_invalidate_range_start){+.+.}, at: try_to_unmap_one
>
> A lock that is taken inside an MMU notifier callback must never be held
> across a reclaiming allocation, so the fs_reclaim annotation does not
> belong inside the notifier_lock region. Drop it. The remaining chain
> still teaches the intended lock nesting.
>
> Fixes: 1d0f5838b126 ("drm/amdgpu: Add lockdep annotations for lock ordering
> validation")
> Signed-off-by: Mikhail Gavrilov <[email protected]>
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_lockdep.c | 8 --------
> 1 file changed, 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_lockdep.c
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_lockdep.c
> index d5d71fd7c70d..eeb3b5007f80 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_lockdep.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_lockdep.c
> @@ -150,12 +150,6 @@ int amdgpu_lockdep_init(void)
> /* Level 6: Reset control lock */
> mutex_lock(&reset_ctl.reset_lock);
>
> - /*
> - * Mark potential memory reclaim boundary.
> - * GPU operations might trigger memory allocation/reclaim.
> - */
> - fs_reclaim_acquire(GFP_KERNEL);
> -
This shouldn't be removed, but instead moved outside the notifier lock.
The notifier lock and vram_lock are also in incorrect order.
@Vitaly can you take care of fixing that? Thanks in advance.
Amdgpus VM eviction lock needs to be handled here as well, but has another
ordering bug with fs_reclaim_acquire().
Patches to fix that are pending on the amdgpu mailing list, but I need to find
time to work on them.
Thanks for the report,
Christian.
> /* Level 7: SRBM register access */
> mutex_lock(&srbm_mutex);
>
> @@ -175,8 +169,6 @@ int amdgpu_lockdep_init(void)
> mutex_unlock(&grbm_idx_mutex);
> mutex_unlock(&srbm_mutex);
>
> - fs_reclaim_release(GFP_KERNEL);
> -
> mutex_unlock(&reset_ctl.reset_lock);
> up_read(&reset_domain->sem);
> mutex_unlock(&vram_lock);
