Re: [PATCH v2] fix AMDGPU failure with periodic signal

[Lorenzo Stoakes <lorenzo.stoakes@oracle.com>]

Andrew,

I'm not sure if the git repos are lagging vs. quilt, but as reported this
patch breaks the VMA tests, and the tests are _still_ broken.

Yet it's still in mm-new, mm-unstable, and even mm-hotfixes-unstable.

This is interfering with my work, can we please drop this.

Also the v3 is currently being debated, so surely should have been dropped
until we have this resolved?

Thanks, Lorenzo

On Fri, Nov 07, 2025 at 06:48:01PM +0100, Mikulas Patocka wrote:
> If a process sets up a timer that periodically sends a signal in short
> intervals and if it uses OpenCL on AMDGPU at the same time, we get random
> errors. Sometimes, probing the OpenCL device fails (strace shows that
> open("/dev/kfd") failed with -EINTR). Sometimes we get the message
> "amdgpu: init_user_pages: Failed to register MMU notifier: -4" in the
> syslog.
>
> The bug can be reproduced with this program:
> http://www.jikos.cz/~mikulas/testcases/opencl/opencl-bug-small.c
>
> The root cause for these failures is in the function mm_take_all_locks.
> This function fails with -EINTR if there is pending signal. The -EINTR is
> propagated up the call stack to userspace and userspace fails if it gets
> this error.
>
> There is the following call chain: kfd_open -> kfd_create_process ->
> create_process -> mmu_notifier_get -> mmu_notifier_get_locked ->
> __mmu_notifier_register -> mm_take_all_locks -> "return -EINTR"
>
> If the failure happens in init_user_pages, there is the following call
> chain: init_user_pages -> amdgpu_hmm_register ->
> mmu_interval_notifier_insert -> mmu_notifier_register ->
> __mmu_notifier_register -> mm_take_all_locks -> "return -EINTR"
>
> In order to fix these failures, this commit changes
> signal_pending(current) to fatal_signal_pending(current) in
> mm_take_all_locks, so that it is interrupted only if the signal is
> actually killing the process.
>
> Also, this commit skips pr_err in init_user_pages if the process is being
> killed - in this situation, there was no error and so we don't want to
> report it in the syslog.
>
> I'm submitting this patch for the stable kernels, because this bug may
> cause random failures in any OpenCL code.
>
> Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
> Cc: stable@vger.kernel.org
>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c |    9 +++++++--
>  mm/vma.c                                         |    8 ++++----
>  2 files changed, 11 insertions(+), 6 deletions(-)
>
> Index: linux-6.17.7/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> ===================================================================
> --- linux-6.17.7.orig/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> +++ linux-6.17.7/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> @@ -1069,8 +1069,13 @@ static int init_user_pages(struct kgd_me
>
>  	ret = amdgpu_hmm_register(bo, user_addr);
>  	if (ret) {
> -		pr_err("%s: Failed to register MMU notifier: %d\n",
> -		       __func__, ret);
> +		/*
> +		 * If we got EINTR because the process was killed, don't report
> +		 * it, because no error happened.
> +		 */
> +		if (!(fatal_signal_pending(current) && ret == -EINTR))
> +			pr_err("%s: Failed to register MMU notifier: %d\n",
> +			       __func__, ret);
>  		goto out;
>  	}
>
> Index: linux-6.17.7/mm/vma.c
> ===================================================================
> --- linux-6.17.7.orig/mm/vma.c
> +++ linux-6.17.7/mm/vma.c
> @@ -2175,14 +2175,14 @@ int mm_take_all_locks(struct mm_struct *
>  	 * is reached.
>  	 */
>  	for_each_vma(vmi, vma) {
> -		if (signal_pending(current))
> +		if (fatal_signal_pending(current))
>  			goto out_unlock;
>  		vma_start_write(vma);
>  	}
>
>  	vma_iter_init(&vmi, mm, 0);
>  	for_each_vma(vmi, vma) {
> -		if (signal_pending(current))
> +		if (fatal_signal_pending(current))
>  			goto out_unlock;
>  		if (vma->vm_file && vma->vm_file->f_mapping &&
>  				is_vm_hugetlb_page(vma))
> @@ -2191,7 +2191,7 @@ int mm_take_all_locks(struct mm_struct *
>
>  	vma_iter_init(&vmi, mm, 0);
>  	for_each_vma(vmi, vma) {
> -		if (signal_pending(current))
> +		if (fatal_signal_pending(current))
>  			goto out_unlock;
>  		if (vma->vm_file && vma->vm_file->f_mapping &&
>  				!is_vm_hugetlb_page(vma))
> @@ -2200,7 +2200,7 @@ int mm_take_all_locks(struct mm_struct *
>
>  	vma_iter_init(&vmi, mm, 0);
>  	for_each_vma(vmi, vma) {
> -		if (signal_pending(current))
> +		if (fatal_signal_pending(current))
>  			goto out_unlock;
>  		if (vma->anon_vma)
>  			list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
>
>