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

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Date:   Tue, 24 Apr 2018 15:52:45 +0000
From:   "Panariti, David" <David.Panariti@....com>
To:     "Grodzovsky, Andrey" <Andrey.Grodzovsky@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "amd-gfx@...ts.freedesktop.org" <amd-gfx@...ts.freedesktop.org>
CC:     "Deucher, Alexander" <Alexander.Deucher@....com>,
        "Koenig, Christian" <Christian.Koenig@....com>,
        "oleg@...hat.com" <oleg@...hat.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "ebiederm@...ssion.com" <ebiederm@...ssion.com>,
        "Grodzovsky, Andrey" <Andrey.Grodzovsky@....com>
Subject: RE: [PATCH 3/3] drm/amdgpu: Switch to interrupted wait to recover
 from ring hang.

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@....com> 
Sent: Tuesday, April 24, 2018 11:31 AM
To: linux-kernel@...r.kernel.org; amd-gfx@...ts.freedesktop.org
Cc: Deucher, Alexander <Alexander.Deucher@....com>; Koenig, Christian <Christian.Koenig@....com>; Panariti, David <David.Panariti@....com>; oleg@...hat.com; akpm@...ux-foundation.org; ebiederm@...ssion.com; Grodzovsky, Andrey <Andrey.Grodzovsky@....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@....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;
+			}
 		}
 	}
 
--
2.7.4