linux-kernel - [PATCH AUTOSEL 6.6 19/23] drm/amdgpu: grab an additional reference on the gang fence v2

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Message-Id: <20250403191816.2681439-19-sashal@kernel.org>
Date: Thu,  3 Apr 2025 15:18:12 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Christian König <christian.koenig@....com>,
	Srinivasan Shanmugam <srinivasan.shanmugam@....com>,
	Alex Deucher <alexander.deucher@....com>,
	Sasha Levin <sashal@...nel.org>,
	airlied@...il.com,
	simona@...ll.ch,
	lijo.lazar@....com,
	sunil.khatri@....com,
	Hawking.Zhang@....com,
	Jun.Ma2@....com,
	Yunxiang.Li@....com,
	amd-gfx@...ts.freedesktop.org,
	dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 6.6 19/23] drm/amdgpu: grab an additional reference on the gang fence v2

From: Christian König <christian.koenig@....com>

[ Upstream commit 0d9a95099dcb05b5f4719c830d15bf4fdcad0dc2 ]

We keep the gang submission fence around in adev, make sure that it
stays alive.

v2: fix memory leak on retry

Signed-off-by: Christian König <christian.koenig@....com>
Acked-by: Srinivasan Shanmugam <srinivasan.shanmugam@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
index 45dd6cbad81e7..10f5a3d0f5916 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
@@ -6015,6 +6015,7 @@ struct dma_fence *amdgpu_device_switch_gang(struct amdgpu_device *adev,
 {
 	struct dma_fence *old = NULL;
 
+	dma_fence_get(gang);
 	do {
 		dma_fence_put(old);
 		rcu_read_lock();
@@ -6024,12 +6025,19 @@ struct dma_fence *amdgpu_device_switch_gang(struct amdgpu_device *adev,
 		if (old == gang)
 			break;
 
-		if (!dma_fence_is_signaled(old))
+		if (!dma_fence_is_signaled(old)) {
+			dma_fence_put(gang);
 			return old;
+		}
 
 	} while (cmpxchg((struct dma_fence __force **)&adev->gang_submit,
 			 old, gang) != old);
 
+	/*
+	 * Drop it once for the exchanged reference in adev and once for the
+	 * thread local reference acquired in amdgpu_device_get_gang().
+	 */
+	dma_fence_put(old);
 	dma_fence_put(old);
 	return NULL;
 }
-- 
2.39.5