Re: Workqueues splat due to ending up on wrong CPU

[Paul E. McKenney]

On Thu, Nov 28, 2019 at 08:18:23AM -0800, Paul E. McKenney wrote:
> On Wed, Nov 27, 2019 at 07:50:27AM -0800, Paul E. McKenney wrote:

[ . . . ]

> And still -ENOREPRODUCE.  It did happen on this system with
> hyperthreading, so the next step is to make rcutorture better tolerate
> very large hyperthreaded systems and try again.

[ . . . ]

And hyperthreading seems to have done the trick!  One splat thus far,
shown below.  The run should complete this evening, Pacific Time.

							Thanx, Paul

------------------------------------------------------------------------

[29139.777628] ------------[ cut here ]------------
[29139.779342] expected on cpu 0 but on cpu 2, pool 0, workfn=sync_rcu_exp_select_node_cpus
[29139.780564] WARNING: CPU: 2 PID: 4 at kernel/workqueue.c:2186 process_one_work+0x53b/0x550
[29139.781854] Modules linked in:
[29139.782376] CPU: 2 PID: 4 Comm: rcu_par_gp Not tainted 5.4.0-rc1+ #35
[29139.783418] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.11.0-2.el7 04/01/2014
[29139.784701] Workqueue:  0x0 (rcu_par_gp)
[29139.785308] RIP: 0010:process_one_work+0x53b/0x550
[29139.786058] Code: 99 0f 0b eb d2 c6 05 3c dd 6d 01 01 65 8b 15 64 78 b8 74 41 8b 4c 24 40 4c 8b 43 18 48 c7 c7 08 72 6c 8c 31 c0 e8 55 08 fe ff <0f> 0b e9 53 fb ff ff 0f 1f 40 00 66 2e 0f 1f 84 00 00 00 00 00 41
[29139.788978] RSP: 0000:ffff91d7c002fe30 EFLAGS: 00010086
[29139.789766] RAX: 0000000000000000 RBX: ffffffff8ca65f68 RCX: ffff91d7c002fcdc
[29139.790851] RDX: 0000000000000002 RSI: ffffffff8ca627d8 RDI: 00000000ffffffff
[29139.791982] RBP: ffff8d369ec95600 R08: 0000000000000001 R09: 0000000000000000
[29139.793129] R10: 757063206e6f2074 R11: 7562203020757063 R12: ffff8d369f228a80
[29139.794219] R13: ffff8d369f22d400 R14: 0000000000000000 R15: ffff8d369ec95600
[29139.795316] FS:  0000000000000000(0000) GS:ffff8d369f280000(0000) knlGS:0000000000000000
[29139.796596] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[29139.797509] CR2: 0000000000000148 CR3: 000000001a81e000 CR4: 00000000000006e0
[29139.798625] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[29139.799752] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[29139.801185] Call Trace:
[29139.801765]  rescuer_thread+0x1b5/0x2e0
[29139.802544]  kthread+0xf3/0x130
[29139.803054]  ? worker_thread+0x3c0/0x3c0
[29139.803664]  ? kthread_cancel_delayed_work_sync+0x10/0x10
[29139.804730]  ret_from_fork+0x35/0x40
[29139.805338] ---[ end trace a630d585ddfc6bd2 ]---