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Date:   Mon, 25 Nov 2019 08:17:29 +0100
From:   Juri Lelli <juri.lelli@gmail.com>
To:     Udo van den Heuvel <udovdh@xs4all.nl>
Cc:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        RT <linux-rt-users@vger.kernel.org>
Subject: Re: 5.2.21-rt13 WARN_ON(rt_mutex_owner(lock) != current)
Message-ID: <20191125071729.GH23227@localhost.localdomain>
References: <1dd8d3b0-1fb3-c9fd-a4c3-935d60f0b034@xs4all.nl>
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In-Reply-To: <1dd8d3b0-1fb3-c9fd-a4c3-935d60f0b034@xs4all.nl>
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Hi,

On 24/11/19 07:08, Udo van den Heuvel wrote:
> Hello,
> 
> Is the WARNING below rt-specific or what is happening here?
> Please advise...
> 
> 
> [  600.401576] ------------[ cut here ]------------
> [  600.401583] DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current)
> [  600.401592] WARNING: CPU: 3 PID: 23306 at
> kernel/locking/rtmutex-debug.c:145 debug_rt_mutex_unlock+0x48/0x50
> [  600.401606] Modules linked in: act_police sch_ingress cls_u32 sch_sfq
> sch_cbq pppoe pppox ip6table_raw nf_log_ipv6 ip6table_mangle xt_u32
> xt_CT xt_nat nf_log_ipv4 nf_log_common xt_statistic nf_nat_sip
> nf_conntrack_sip xt_recent xt_string xt_lscan(O) xt_TARPIT(O)
> iptable_raw nf_nat_h323 nf_conn
> track_h323 xt_TCPMSS xt_length xt_hl xt_tcpmss xt_owner xt_mac xt_mark
> xt_multiport xt_limit nf_nat_irc nf_conntrack_irc xt_LOG xt_DSCP
> xt_REDIRECT xt_MASQUERADE xt_dscp nf_nat_ftp nf_conntrack_ftp
> iptable_mangle iptable_nat mq_deadline 8021q ipt_REJECT nf_reject_ipv4
> iptable_filter ip6t_REJECT n
> f_reject_ipv6 xt_state xt_conntrack ip6table_filter nct6775 ip6_tables
> sunrpc amd_freq_sensitivity aesni_intel pl2303 aes_x86_64 amdgpu
> snd_hda_codec_realtek glue_helper mfd_core snd_hda_codec_generic
> crypto_simd cryptd gpu_sched drm_kms_helper syscopyarea sysfillrect
> sysimgblt i2c_piix4 fb_sys_f
> ops snd_hda_codec_hdmi ttm drm drm_panel_orientation_quirks cfbfillrect
> snd_hda_intel cfbimgblt snd_hda_codec
> [  600.401695]  cfbcopyarea snd_hda_core i2c_algo_bit snd_pcm fb fbdev
> snd_timer backlight snd acpi_cpufreq sr_mod cdrom sd_mod autofs4
> [  600.401710] CPU: 3 PID: 23306 Comm: fsfreeze Tainted: G           O
>    5.2.21-rt13 #9
> [  600.401714] Hardware name: To Be Filled By O.E.M. To Be Filled By
> O.E.M./QC5000M-ITX/PH, BIOS P1.10 05/06/2015
> [  600.401716] RIP: 0010:debug_rt_mutex_unlock+0x48/0x50
> [  600.401721] Code: 75 02 f3 c3 e8 99 47 21 00 85 c0 74 f5 8b 05 ef 08
> 04 01 85 c0 75 eb 48 c7 c6 50 f9 d7 81 48 c7 c7 48 06 d7 81 e8 a9 29 fb
> ff <0f> 0b c3 0f 1f 44 00 00 f3 c3 66 66 2e 0f 1f 84 00 00 00 00 00 0f
> [  600.401726] RSP: 0018:ffffc900027d3d80 EFLAGS: 00010082
> [  600.401727] RAX: 0000000000000000 RBX: ffff888136d6eb80 RCX:
> ffffffff820708d8
> [  600.401730] RDX: ffffffff82070a00 RSI: 0000000000000000 RDI:
> ffffffff82070c50
> [  600.401732] RBP: ffff888136d6e918 R08: ffffffff820708c0 R09:
> 0000000000000001
> [  600.401734] R10: ffffffff82070900 R11: ffffc900027d3cc0 R12:
> 0000000000000292
> [  600.401735] R13: ffffc900027d3d98 R14: ffff888136d6e470 R15:
> ffffffff81162a0a
> [  600.401738] FS:  00007f6b80d9d540(0000) GS:ffff88813b380000(0000)
> knlGS:0000000000000000
> [  600.401740] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [  600.401742] CR2: 00007fc4a87fe430 CR3: 000000006382c000 CR4:
> 00000000000406a0
> [  600.401745] Call Trace:
> [  600.401750]  __rt_mutex_unlock+0x56/0xd0
> [  600.401758]  percpu_up_write+0x1a/0x30
> [  600.401763]  thaw_super_locked+0x10a/0x140
> [  600.401769]  ? thaw_super_locked+0xaa/0x140
> [  600.401773]  do_vfs_ioctl+0x5a4/0x6a0
> [  600.401778]  ? __se_sys_newfstat+0x5a/0x70
> [  600.401782]  ksys_ioctl+0x7b/0xa0
> [  600.401785]  __x64_sys_ioctl+0x11/0x20
> [  600.401788]  do_syscall_64+0x6d/0x310
> [  600.401794]  ? __do_page_fault+0x242/0x510
> [  600.401798]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> [  600.401803] RIP: 0033:0x7f6b80ccb34b
> [  600.401806] Code: 0f 1e fa 48 8b 05 3d 9b 0c 00 64 c7 00 26 00 00 00
> 48 c7 c0 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa b8 10 00 00 00 0f
> 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 0d 9b 0c 00 f7 d8 64 89 01 48
> [  600.401811] RSP: 002b:00007ffecbbd7c48 EFLAGS: 00000246 ORIG_RAX:
> 0000000000000010
> [  600.401812] RAX: ffffffffffffffda RBX: 0000000000000003 RCX:
> 00007f6b80ccb34b
> [  600.401814] RDX: 0000000000000000 RSI: 00000000c0045878 RDI:
> 0000000000000003
> [  600.401816] RBP: 0000000000000003 R08: 0000000000000001 R09:
> 0000000000000000
> [  600.401817] R10: 0000000000000000 R11: 0000000000000246 R12:
> 0000000000000002
> [  600.401819] R13: 00007ffecbbda0fe R14: 0000000000000000 R15:
> 0000000000000000
> [  600.401822] ---[ end trace 0000000000000002 ]---

This looks similar to what I already reported (originally on 4.19-rt).

https://lore.kernel.org/lkml/20190326093421.GA29508@localhost.localdomain/

Peter is working on rewriting percpu_rwsem implementation to fix it.

https://lore.kernel.org/lkml/20191113102115.116470462@infradead.org/

Best,

Juri