[PATCH] drm/amdgpu: install ctx entities with cmpxchg

[Deucher, Alexander]

[Public]

Acked-by: Alex Deucher <alexander.deucher at amd.com>
________________________________
From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> on behalf of Christian König <ckoenig.leichtzumerken at gmail.com>
Sent: Wednesday, February 23, 2022 8:38 AM
To: amd-gfx at lists.freedesktop.org <amd-gfx at lists.freedesktop.org>
Cc: Koenig, Christian <Christian.Koenig at amd.com>; Xue, Ken <Ken.Xue at amd.com>
Subject: [PATCH] drm/amdgpu: install ctx entities with cmpxchg

Since we removed the context lock we need to make sure that not two threads
are trying to install an entity at the same time.

Signed-off-by: Christian König <christian.koenig at amd.com>
Fixes: e68efb27647f ("drm/amdgpu: remove ctx->lock")
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
index f522b52725e4..16eb1ee600ed 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
@@ -204,9 +204,15 @@ static int amdgpu_ctx_init_entity(struct amdgpu_ctx *ctx, u32 hw_ip,
         if (r)
                 goto error_free_entity;

-       ctx->entities[hw_ip][ring] = entity;
+       /* It's not an error if we fail to install the new entity */
+       if (cmpxchg(&ctx->entities[hw_ip][ring], NULL, entity))
+               goto cleanup_entity;
+
         return 0;

+cleanup_entity:
+       drm_sched_entity_fini(&entity->entity);
+
 error_free_entity:
         kfree(entity);

--
2.25.1

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