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Subject: Re: 5.6-rc3: WARNING: CPU: 48 PID: 17435 at kernel/sched/fair.c:380
 enqueue_task_fair+0x328/0x440
From:   Christian Borntraeger <borntraeger@de.ibm.com>
To:     Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
References: <ace7327f-0fd6-4f36-39ae-a8d7d1c7f06b@de.ibm.com>
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Date:   Fri, 28 Feb 2020 13:04:24 +0100
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I was able to reproduce this with 5.5.0


On 28.02.20 08:54, Christian Borntraeger wrote:
> Peter,
> 
> it seems that your new assert did trigger for me:
> 
> The system was running fine for 4 hours and then this happened.
> Unfortunately I have no idea if this reproduces and if so how.
> 
> [15260.753944] ------------[ cut here ]------------
> [15260.753949] rq->tmp_alone_branch != &rq->leaf_cfs_rq_list
> [15260.753959] WARNING: CPU: 48 PID: 17435 at kernel/sched/fair.c:380 enqueue_task_fair+0x328/0x440
> [15260.753961] Modules linked in: kvm xt_CHECKSUM xt_MASQUERADE nf_nat_tftp nf_conntrack_tftp xt_CT tun bridge stp llc xt_tcpudp ip6t_REJECT nf_reject_ipv6 ip6t_rpfilter ipt_REJECT nf_reject_ipv4 xt_conntrack ip6table_nat ip6table_mangle ip6table_raw ip6table_security iptable_nat nf_nat iptable_mangle iptable_raw iptable_security nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ip_set nfnetlink ip6table_filter ip6_tables iptable_filter rpcrdma sunrpc rdma_ucm rdma_cm iw_cm ib_cm configfs s390_trng mlx5_ib ghash_s390 prng ib_uverbs aes_s390 ib_core des_s390 libdes sha3_512_s390 genwqe_card vfio_ccw vfio_mdev sha3_256_s390 mdev crc_itu_t sha512_s390 vfio_iommu_type1 sha1_s390 vfio eadm_sch zcrypt_cex4 sch_fq_codel ip_tables x_tables mlx5_core sha256_s390 sha_common pkey zcrypt rng_core autofs4
> [15260.754002] CPU: 48 PID: 17435 Comm: cc1 Not tainted 5.6.0-rc3+ #24
> [15260.754004] Hardware name: IBM 3906 M04 704 (LPAR)
> [15260.754005] Krnl PSW : 0404c00180000000 0000000942282e3c (enqueue_task_fair+0x32c/0x440)
> [15260.754008]            R:0 T:1 IO:0 EX:0 Key:0 M:1 W:0 P:0 AS:3 CC:0 PM:0 RI:0 EA:3
> [15260.754010] Krnl GPRS: 00000000000003e0 0000001fbd60ee00 000000000000002d 00000009435347c2
> [15260.754012]            000000000000002c 00000009428ec950 0000000900000000 0000000000000001
> [15260.754013]            0000001fbd60ed00 0000001fbd60ed00 0000001fbd60ee00 0000000000000000
> [15260.754014]            0000001c633ea000 0000000942c34670 0000000942282e38 000003e00140baf8
> [15260.754066] Krnl Code: 0000000942282e2c: c020005d39d8	larl	%r2,0000000942e2a1dc
>                           0000000942282e32: c0e5fffdcc3f	brasl	%r14,000000094223c6b0
>                          #0000000942282e38: af000000		mc	0,0
>                          >0000000942282e3c: a7f4ff22		brc	15,0000000942282c80
>                           0000000942282e40: 41b06340		la	%r11,832(%r6)
>                           0000000942282e44: e3d063480004	lg	%r13,840(%r6)
>                           0000000942282e4a: b904004b		lgr	%r4,%r11
>                           0000000942282e4e: b904003d		lgr	%r3,%r13
> [15260.754080] Call Trace:
> [15260.754083]  [<0000000942282e3c>] enqueue_task_fair+0x32c/0x440 
> [15260.754085] ([<0000000942282e38>] enqueue_task_fair+0x328/0x440)
> [15260.754087]  [<0000000942272d78>] activate_task+0x88/0xf0 
> [15260.754088]  [<00000009422732e8>] ttwu_do_activate+0x58/0x78 
> [15260.754090]  [<00000009422742ce>] try_to_wake_up+0x256/0x650 
> [15260.754093]  [<000000094229248e>] swake_up_locked.part.0+0x2e/0x70 
> [15260.754095]  [<00000009422927ac>] swake_up_one+0x54/0x88 
> [15260.754151]  [<000003ff8044c15a>] kvm_vcpu_wake_up+0x52/0x78 [kvm] 
> [15260.754161]  [<000003ff8046af02>] kvm_s390_vcpu_wakeup+0x2a/0x40 [kvm] 
> [15260.754171]  [<000003ff8046b68e>] kvm_s390_idle_wakeup+0x6e/0xa0 [kvm] 
> [15260.754175]  [<00000009422dd05c>] __hrtimer_run_queues+0x114/0x2f0 
> [15260.754178]  [<00000009422dddb4>] hrtimer_interrupt+0x12c/0x2a8 
> [15260.754181]  [<0000000942200d3c>] do_IRQ+0xac/0xb0 
> [15260.754185]  [<0000000942c25684>] ext_int_handler+0x130/0x134 
> [15260.754186] Last Breaking-Event-Address:
> [15260.754189]  [<000000094223c710>] __warn_printk+0x60/0x68
> [15260.754190] ---[ end trace e84a48be72a8b514 ]---
>