drm/ttm: ttm_bo_release called without lock

[Christian König]

Hi Petr,

yes that is a known bug in qxl and yes the patch you mentioned makes it 
worse.

Going to reduce the warning into a WARN_ON_ONCE().

Regards,
Christian.

Am 03.03.21 um 15:34 schrieb Petr Mladek:
> Hi,
>
> the following warning is filling my kernel log buffer
> with 5.12-rc1+ kernels:
>
> [  941.070598] WARNING: CPU: 0 PID: 11 at drivers/gpu/drm/ttm/ttm_bo.c:139 ttm_bo_move_to_lru_tail+0x1ba/0x210
> [  941.070601] Modules linked in:
> [  941.070603] CPU: 0 PID: 11 Comm: kworker/0:1 Kdump: loaded Tainted: G        W         5.12.0-rc1-default+ #81
> [  941.070605] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-59-gc9ba527-rebuilt.opensuse.org 04/01/2014
> [  941.070606] Workqueue: events qxl_gc_work
> [  941.070609] RIP: 0010:ttm_bo_move_to_lru_tail+0x1ba/0x210
> [  941.070610] Code: 93 e8 02 00 00 48 89 0a e9 00 ff ff ff 48 8b 87 38 01 00 00 be ff ff ff ff 48 8d 78 70 e8 8e 7d 46 00 85 c0 0f 85 6f fe ff ff <0f> 0b 8b 93 fc 02 00 00 85 d2 0f 84 6d fe ff ff 48 89 df 5b 5d 41
> [  941.070612] RSP: 0018:ffffbddf4008fd38 EFLAGS: 00010246
> [  941.070614] RAX: 0000000000000000 RBX: ffff95ae485bac00 RCX: 0000000000000002
> [  941.070615] RDX: 0000000000000000 RSI: ffff95ae485badb0 RDI: ffff95ae40305108
> [  941.070616] RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000001
> [  941.070617] R10: ffffbddf4008fc10 R11: ffffffffa5401580 R12: ffff95ae42a94e90
> [  941.070618] R13: ffff95ae485bae70 R14: ffff95ae485bac00 R15: ffff95ae455d1800
> [  941.070620] FS:  0000000000000000(0000) GS:ffff95aebf600000(0000) knlGS:0000000000000000
> [  941.070621] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [  941.070622] CR2: 00007f8ffb2f8000 CR3: 0000000102c5e005 CR4: 0000000000370ef0
> [  941.070624] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [  941.070626] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> [  941.070627] Call Trace:
> [  941.070630]  ttm_bo_release+0x551/0x600
> [  941.070635]  qxl_bo_unref+0x3a/0x50
> [  941.070638]  qxl_release_free_list+0x62/0xc0
> [  941.070643]  qxl_release_free+0x76/0xe0
> [  941.070646]  qxl_garbage_collect+0xd9/0x190
> [  941.080241]  process_one_work+0x2b0/0x630
> [  941.080249]  ? process_one_work+0x630/0x630
> [  941.080251]  worker_thread+0x39/0x3f0
> [  941.080255]  ? process_one_work+0x630/0x630
> [  941.080257]  kthread+0x13a/0x150
> [  941.080260]  ? kthread_create_worker_on_cpu+0x70/0x70
> [  941.080265]  ret_from_fork+0x1f/0x30
> [  941.080277] irq event stamp: 757191
> [  941.080278] hardirqs last  enabled at (757197): [<ffffffffa217431f>] vprintk_emit+0x27f/0x2c0
> [  941.080280] hardirqs last disabled at (757202): [<ffffffffa21742dc>] vprintk_emit+0x23c/0x2c0
> [  941.080281] softirqs last  enabled at (755768): [<ffffffffa300030f>] __do_softirq+0x30f/0x432
> [  941.080284] softirqs last disabled at (755763): [<ffffffffa20eb0aa>] irq_exit_rcu+0xea/0xf0
>
> My wild guess is that it might be related to the commit
> 3d1a88e1051f5d788d789 ("drm/ttm: cleanup LRU handling further").
>
> Does it ring any bell, please?
>
> Best Regards,
> Petr