RE: [PATCH 3/3] drm/amdgpu: Switch to interrupted wait to recover from ring hang.

["Panariti, David" <David.Panariti@amd.com>]

Hi,

It looks like there can be an infinite loop if neither of the if()'s become true.
Is that an impossible condition?

-----Original Message-----
From: Andrey Grodzovsky <andrey.grodzovsky@amd.com> 
Sent: Tuesday, April 24, 2018 11:31 AM
To: linux-kernel@vger.kernel.org; amd-gfx@lists.freedesktop.org
Cc: Deucher, Alexander <Alexander.Deucher@amd.com>; Koenig, Christian <Christian.Koenig@amd.com>; Panariti, David <David.Panariti@amd.com>; oleg@redhat.com; akpm@linux-foundation.org; ebiederm@xmission.com; Grodzovsky, Andrey <Andrey.Grodzovsky@amd.com>
Subject: [PATCH 3/3] drm/amdgpu: Switch to interrupted wait to recover from ring hang.

If the ring is hanging for some reason allow to recover the waiting by sending fatal signal.

Originally-by: David Panariti <David.Panariti@amd.com>
Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.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;
+			}
 		}
 	}
 
--
2.7.4