linux-kernel - Re: [PATCH 3/3] drm/amdgpu: Switch to interrupted wait to recover from ring hang.

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Date:   Mon, 30 Apr 2018 13:34:04 +0200
From:   Christian König <christian.koenig@....com>
To:     Andrey Grodzovsky <andrey.grodzovsky@....com>,
        linux-kernel@...r.kernel.org, amd-gfx@...ts.freedesktop.org
Cc:     Alexander.Deucher@....com, David.Panariti@....com, oleg@...hat.com,
        akpm@...ux-foundation.org, ebiederm@...ssion.com
Subject: Re: [PATCH 3/3] drm/amdgpu: Switch to interrupted wait to recover
 from ring hang.

Am 24.04.2018 um 17:30 schrieb Andrey Grodzovsky:
> If the ring is hanging for some reason allow to recover the waiting
> by sending fatal signal.
>
> Originally-by: David Panariti <David.Panariti@....com>
> Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@....com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c | 14 ++++++++++----
>   1 file changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
> index eb80edf..37a36af 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
> @@ -421,10 +421,16 @@ int amdgpu_ctx_wait_prev_fence(struct amdgpu_ctx *ctx, unsigned ring_id)
>   
>   	if (other) {
>   		signed long r;
> -		r = dma_fence_wait_timeout(other, false, MAX_SCHEDULE_TIMEOUT);
> -		if (r < 0) {
> -			DRM_ERROR("Error (%ld) waiting for fence!\n", r);
> -			return r;
> +
> +		while (true) {
> +			if ((r = dma_fence_wait_timeout(other, true,
> +					MAX_SCHEDULE_TIMEOUT)) >= 0)
> +				return 0;
> +
> +			if (fatal_signal_pending(current)) {
> +				DRM_ERROR("Error (%ld) waiting for fence!\n", r);
> +				return r;
> +			}

Please drop the whole extra handling. The caller is perfectly capable of 
dealing with interrupted waits.

So all we need to do here is change "dma_fence_wait_timeout(other, 
false, ..." into "dma_fence_wait_timeout(other, true, ..." and suppress 
the error message when the IOCTL was just interrupted by a signal.

Regards,
Christian.

>   		}
>   	}
>