drm/kfd: fix a system crash issue during GPU recovery

The crash log as the below:

[Thu Aug 20 23:18:14 2020] general protection fault: 0000 [#1] SMP NOPTI
[Thu Aug 20 23:18:14 2020] CPU: 152 PID: 1837 Comm: kworker/152:1 Tainted: G           OE     5.4.0-42-generic #46~18.04.1-Ubuntu
[Thu Aug 20 23:18:14 2020] Hardware name: GIGABYTE G482-Z53-YF/MZ52-G40-00, BIOS R12 05/13/2020
[Thu Aug 20 23:18:14 2020] Workqueue: events amdgpu_ras_do_recovery [amdgpu]
[Thu Aug 20 23:18:14 2020] RIP: 0010:evict_process_queues_cpsch+0xc9/0x130 [amdgpu]
[Thu Aug 20 23:18:14 2020] Code: 49 8d 4d 10 48 39 c8 75 21 eb 44 83 fa 03 74 36 80 78 72 00 74 0c 83 ab 68 01 00 00 01 41 c6 45 41 00 48 8b 00 48 39 c8 74 25 <80> 78 70 00 c6 40 6d 01 74 ee 8b 50 28 c6 40 70 00 83 ab 60 01 00
[Thu Aug 20 23:18:14 2020] RSP: 0018:ffffb29b52f6fc90 EFLAGS: 00010213
[Thu Aug 20 23:18:14 2020] RAX: 1c884edb0a118914 RBX: ffff8a0d45ff3c00 RCX: ffff8a2d83e41038
[Thu Aug 20 23:18:14 2020] RDX: 0000000000000000 RSI: 0000000000000082 RDI: ffff8a0e2e4178c0
[Thu Aug 20 23:18:14 2020] RBP: ffffb29b52f6fcb0 R08: 0000000000001b64 R09: 0000000000000004
[Thu Aug 20 23:18:14 2020] R10: ffffb29b52f6fb78 R11: 0000000000000001 R12: ffff8a0d45ff3d28
[Thu Aug 20 23:18:14 2020] R13: ffff8a2d83e41028 R14: 0000000000000000 R15: 0000000000000000
[Thu Aug 20 23:18:14 2020] FS:  0000000000000000(0000) GS:ffff8a0e2e400000(0000) knlGS:0000000000000000
[Thu Aug 20 23:18:14 2020] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[Thu Aug 20 23:18:14 2020] CR2: 000055c783c0e6a8 CR3: 00000034a1284000 CR4: 0000000000340ee0
[Thu Aug 20 23:18:14 2020] Call Trace:
[Thu Aug 20 23:18:14 2020]  kfd_process_evict_queues+0x43/0xd0 [amdgpu]
[Thu Aug 20 23:18:14 2020]  kfd_suspend_all_processes+0x60/0xf0 [amdgpu]
[Thu Aug 20 23:18:14 2020]  kgd2kfd_suspend.part.7+0x43/0x50 [amdgpu]
[Thu Aug 20 23:18:14 2020]  kgd2kfd_pre_reset+0x46/0x60 [amdgpu]
[Thu Aug 20 23:18:14 2020]  amdgpu_amdkfd_pre_reset+0x1a/0x20 [amdgpu]
[Thu Aug 20 23:18:14 2020]  amdgpu_device_gpu_recover+0x377/0xf90 [amdgpu]
[Thu Aug 20 23:18:14 2020]  ? amdgpu_ras_error_query+0x1b8/0x2a0 [amdgpu]
[Thu Aug 20 23:18:14 2020]  amdgpu_ras_do_recovery+0x159/0x190 [amdgpu]
[Thu Aug 20 23:18:14 2020]  process_one_work+0x20f/0x400
[Thu Aug 20 23:18:14 2020]  worker_thread+0x34/0x410

When GPU hang, user process will fail to create a compute queue whose
struct object will be freed later, but driver wrongly add this queue to
queue list of the proccess. And then kfd_process_evict_queues will
access a freed memory, which cause a system crash.

v2:
The failure to execute_queues should probably not be reported to
the caller of create_queue, because the queue was already created.
Therefore change to ignore the return value from execute_queues.
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Dennis Li <Dennis.Li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c

@@ -1302,7 +1302,7 @@ static int create_queue_cpsch(struct device_queue_manager *dqm, struct queue *q,
 	if (q->properties.is_active) {
 		increment_queue_count(dqm, q->properties.type);
 
-		retval = execute_queues_cpsch(dqm,
+		execute_queues_cpsch(dqm,
 				KFD_UNMAP_QUEUES_FILTER_DYNAMIC_QUEUES, 0);
 	}