RE: [PATCH] sched/fair: fix select_task_rq_fair return -1

[Zhang, Jun]

Hello, Hillf
This issue happened in 3.14.25. 
Do you know which patch to fix it in 3.18-rc7?
We can try it.

-----Original Message-----
From: Hillf Danton [mailto:hillf.zj@xxxxxxxxxxxxxxx] 
Sent: Thursday, December 04, 2014 5:05 PM
To: Zhang, Jun
Cc: Ingo Molnar; Peter Zijlstra; linux-kernel; Liu, Chuansheng; Liu, Changcheng; Hillf Danton; Vincent Guittot
Subject: Re: [PATCH] sched/fair: fix select_task_rq_fair return -1

> 
> From: zhang jun <jun.zhang@xxxxxxxxx>
> 
> when cpu == -1 and sd->child == NULL, select_task_rq_fair return -1, system panic.
> 
> [ 0.738326] BUG: unable to handle kernel paging request at 
> ffff8800997ea928 [ 0.746138] IP: [<ffffffff810b15d3>] 
> wake_up_new_task+0x43/0x1b0 [ 0.752886] PGD 25df067 PUD 0 [ 0.756321] 
> Oops: 0000 1 PREEMPT SMP [ 0.760743] Modules linked in:
> [ 0.764179] CPU: 0 PID: 6 Comm: kworker/u8:0 Not tainted 
> 3.14.19-quilt-b27ac761 #2 [ 0.772651] Hardware name: Intel Corporation 
> CHERRYVIEW B1 PLATFORM/Cherry Trail CR, BIOS 
> CHTTRVP1.X64.0003.R08.1411110453
> 11/11/2014
> [ 0.786084] Workqueue: khelper __call_usermodehelper [ 0.791649] task: 
> ffff88007955a150 ti: ffff88007955c000 task.ti: ffff88007955c000 [ 
> 0.800021] RIP: 0010:[<ffffffff810b15d3>] [<ffffffff810b15d3>] 
> wake_up_new_task+0x43/0x1b0 [ 0.809478] RSP: 0000:ffff88007955dd58 
> EFLAGS: 00010092 [ 0.815422] RAX: 00000000ffffffff RBX: 
> 0000000000000001 RCX: 0000000000000020 [ 0.823404] RDX: 
> 00000000ffffffff RSI: 0000000000000020 RDI: 0000000000000020 [ 
> 0.831386] RBP: ffff88007955dd80 R08: ffff880079604b58 R09: 
> 00000000ffffffff [ 0.839368] R10: 0000000000000004 R11: 
> eae0000000000000 R12: ffff8800797ea650 [ 0.847350] R13: 
> 0000000000004000 R14: ffff8800797ead52 R15: 0000000000000206 [ 
> 0.855335] FS: 0000000000000000(0000) GS:ffff88007aa00000(0000) 
> knlGS:0000000000000000 [ 0.864387] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b [ 0.870817] CR2: ffff8800997ea928 CR3: 000000000220b000 CR4: 00000000001007f0 [ 0.878796] Stack:
> [ 0.881046] 0000000000000001 ffff8800797ea650 0000000000004000 
> 0000000000000000 [ 0.889363] 000000000000003c ffff88007955ddf0 
> ffffffff8107ddfd ffffffff810b6a95 [ 0.897680] 0000000000000000 
> ffff8800796beb00 ffff880000000000 ffffffff81000000 [ 0.905998] Call Trace:
> [ 0.908752] [<ffffffff8107ddfd>] do_fork+0x12d/0x3b0 [ 0.914416] 
> [<ffffffff810b6a95>] ? set_next_entity+0x95/0xb0 [ 0.920856] 
> [<ffffffff8107e0a6>] kernel_thread+0x26/0x30 [ 0.926903] 
> [<ffffffff8109703e>] __call_usermodehelper+0x2e/0x90 [ 0.933730] 
> [<ffffffff8109ad31>] process_one_work+0x171/0x490 [ 0.940264] 
> [<ffffffff8109ba4b>] worker_thread+0x11b/0x3a0 [ 0.946508] 
> [<ffffffff8109b930>] ? manage_workers.isra.27+0x2b0/0x2b0
> [ 0.953821] [<ffffffff810a1802>] kthread+0xd2/0xf0 [ 0.959289] 
> [<ffffffff810a1730>] ? kthread_create_on_node+0x170/0x170
> [ 0.966602] [<ffffffff81af81ac>] ret_from_fork+0x7c/0xb0 [ 0.972652] 
> [<ffffffff810a1730>] ? kthread_create_on_node+0x170/0x170
> [ 0.979956] Code: 49 89 fc 4c 89 f7 53 e8 bc 5c a4 00 49 8b 54 24 08 
> 31 c9 49 89 c7 49 8b 44 24 60 4c 89 e7 8b 72 18 ba 08 00 00 00 ff 50 
> 40 89
> c2 <49> 0f a3 94 24 e0 02 00 00 19 c9 85 c9 0f 84 34 01 00 00 48 8b [ 
> 1.001809] RIP [<ffffffff810b15d3>] wake_up_new_task+0x43/0x1b0 [ 
> 1.008641] RSP <ffff88007955dd58> [ 1.012544] CR2: ffff8800997ea928 [ 
> 1.016279] --[ end trace 9737aaa337a5ca10 ]--
> 
> Signed-off-by: zhang jun <jun.zhang@xxxxxxxxx>
> Signed-off-by: Chuansheng Liu <chuansheng.liu@xxxxxxxxx>
> Signed-off-by: Changcheng Liu <changcheng.liu@xxxxxxxxx>
> ---
>  kernel/sched/fair.c |    2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 
> 34baa60..123153f 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4587,6 +4587,8 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_f
>  		if (new_cpu == -1 || new_cpu == cpu) {
>  			/* Now try balancing at a lower domain level of cpu */
>  			sd = sd->child;
> +			if ((!sd) && (new_cpu == -1))
> +				new_cpu = smp_processor_id();
>  			continue;
>  		}
> 
In 3.18-rc7 is -1 still selected?

Hillf