On 12/11/25 16:08, Philipp Stanner wrote:

On Thu, 2025-12-11 at 13:16 +0100, Christian König wrote:

...

This allows amdkfd_fences to outlive the amdgpu module.

v2: implement Felix suggestion to lock the fence while signaling it. v3: fix typos v4: fix return code in signal_eviction_fence

Signed-off-by: Christian König christian.koenig@amd.com

drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h    |  7 +++  .../gpu/drm/amd/amdgpu/amdgpu_amdkfd_fence.c  | 44 +++++++++----------  drivers/gpu/drm/amd/amdkfd/kfd_process.c      |  2 +-  drivers/gpu/drm/amd/amdkfd/kfd_svm.c          |  4 +-  4 files changed, 31 insertions(+), 26 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h index 8bdfcde2029b..2f2b277cfaed 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h @@ -196,6 +196,7 @@ int kfd_debugfs_kfd_mem_limits(struct seq_file *m, void *data);  #endif  #if IS_ENABLED(CONFIG_HSA_AMD)  bool amdkfd_fence_check_mm(struct dma_fence *f, struct mm_struct *mm); +bool amdkfd_fence_signal(struct dma_fence *f);  struct amdgpu_amdkfd_fence *to_amdgpu_amdkfd_fence(struct dma_fence *f);  void amdgpu_amdkfd_remove_all_eviction_fences(struct amdgpu_bo *bo);  int amdgpu_amdkfd_evict_userptr(struct mmu_interval_notifier *mni, @@ -210,6 +211,12 @@ bool amdkfd_fence_check_mm(struct dma_fence *f, struct mm_struct *mm)   return false;  }   +static inline +bool amdkfd_fence_signal(struct dma_fence *f) +{

• return false;

+}

Huh? What's that?

That function seems to be just a NOP. It's return code is used nowhere, is it?

It's the dummy which is used when CONFIG_HSA_AMD isn't enabled.

Not sure if it's actually used or not, but we have dummies for all functions declared in this file.

...

static inline  struct amdgpu_amdkfd_fence *to_amdgpu_amdkfd_fence(struct dma_fence *f)  { diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_fence.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_fence.c index 09c919f72b6c..9cd413e325f0 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_fence.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_fence.c @@ -127,29 +127,9 @@ static bool amdkfd_fence_enable_signaling(struct dma_fence *f)   if (!svm_range_schedule_evict_svm_bo(fence))   return true;   }

• return false;

-}

-/**

• • amdkfd_fence_release - callback that fence can be freed
• • @f: dma_fence
• • This function is called when the reference count becomes zero.
• • Drops the mm_struct reference and RCU schedules freeing up the fence.
• */

-static void amdkfd_fence_release(struct dma_fence *f) -{

• struct amdgpu_amdkfd_fence *fence = to_amdgpu_amdkfd_fence(f);
• /* Unconditionally signal the fence. The process is getting

• * terminated.
  

• */
  

• if (WARN_ON(!fence))

• return; /* Not an amdgpu_amdkfd_fence */
  

mmdrop(fence->mm);

• kfree_rcu(f, rcu);

• fence->mm = NULL;
• return false;

}    /** @@ -174,9 +154,27 @@ bool amdkfd_fence_check_mm(struct dma_fence *f, struct mm_struct *mm)   return false;  }   +bool amdkfd_fence_signal(struct dma_fence *f) +{

• struct amdgpu_amdkfd_fence *fence = to_amdgpu_amdkfd_fence(f);
• unsigned long flags;
• bool was_signaled;
• dma_fence_lock_irqsave(f, flags);
• if (fence->mm) {

• mmdrop(fence->mm);
  

• fence->mm = NULL;
  

• }
• was_signaled = dma_fence_is_signaled_locked(f);
• if (!was_signaled)

• dma_fence_signal_locked(f);
  

• dma_fence_unlock_irqrestore(f, flags);
• return was_signaled;

+}

static const struct dma_fence_ops amdkfd_fence_ops = {   .get_driver_name = amdkfd_fence_get_driver_name,   .get_timeline_name = amdkfd_fence_get_timeline_name,   .enable_signaling = amdkfd_fence_enable_signaling,

• .release = amdkfd_fence_release,

}; diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c b/drivers/gpu/drm/amd/amdkfd/kfd_process.c index bb252ec43733..2cf39e3d3fae 100644 --- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c +++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c @@ -1173,7 +1173,7 @@ static void kfd_process_wq_release(struct work_struct *work)   synchronize_rcu();   ef = rcu_access_pointer(p->ef);   if (ef)

• dma_fence_signal(ef);
  

• amdkfd_fence_signal(ef);
  

kfd_process_remove_sysfs(p);   kfd_debugfs_remove_process(p); diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c index 97c2270f278f..0e94f3a976b1 100644 --- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c +++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c @@ -428,7 +428,7 @@ static void svm_range_bo_release(struct kref *kref)     if (!dma_fence_is_signaled(&svm_bo->eviction_fence->base))   /* We're not in the eviction worker. Signal the fence. */

• dma_fence_signal(&svm_bo->eviction_fence->base);
  

• amdkfd_fence_signal(&svm_bo->eviction_fence->base);
  

dma_fence_put(&svm_bo->eviction_fence->base);   amdgpu_bo_unref(&svm_bo->bo);   kfree(svm_bo); @@ -3628,7 +3628,7 @@ static void svm_range_evict_svm_bo_worker(struct work_struct *work)   mmap_read_unlock(mm);   mmput(mm);

• dma_fence_signal(&svm_bo->eviction_fence->base);

• amdkfd_fence_signal(&svm_bo->eviction_fence->base);

And why do you do those changes and why doesn't the commit message explain it?

You stop signalling those fences, after all.

Hui? I don't stop signaling the fences. I just delegate signaling into a separate helper function which does some extra cleanup before signaling the fence.

Regards, Christian.

P.

...

/* This is the last reference to svm_bo, after svm_range_vram_node_free   * has been called in svm_migrate_vram_to_ram