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Subject: Re: [ANNOUNCE] v5.14-rc5-rt8
To:     Clark Williams <williams@redhat.com>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        LKML <linux-kernel@vger.kernel.org>,
        RT <linux-rt-users@vger.kernel.org>
References: <20210810163731.2qvfuhenolq2gdlv@linutronix.de>
 <20210812151803.52f84aaf@theseus.lan>
From:   Vlastimil Babka <vbabka@suse.cz>
Message-ID: <5f0c793d-5084-4607-8475-209fa7310ba2@suse.cz>
Date:   Thu, 12 Aug 2021 22:45:19 +0200
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On 8/12/21 10:18 PM, Clark Williams wrote:
> On Tue, 10 Aug 2021 18:37:31 +0200
> Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote:
> 
> Sebastian, et al,
> 
> Got the following panic running v5.14-rc5-rt8:
> 
> Aug 13 06:35:05 oberon kernel: page:000000009ac5dd73 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1ab3db
> Aug 13 06:35:05 oberon kernel: flags: 0x17ffffc0000000(node=0|zone=2|lastcpupid=0x1fffff)
> Aug 13 06:35:05 oberon kernel: raw: 0017ffffc0000000 ffffee1286aceb88 ffffee1287b66288 0000000000000000
> Aug 13 06:35:05 oberon kernel: raw: 0000000000000000 0000000000100000 00000000ffffffff 0000000000000000
> Aug 13 06:35:05 oberon kernel: page dumped because: VM_BUG_ON_PAGE(!PageSlab(page))
> Aug 13 06:35:05 oberon kernel: ------------[ cut here ]------------
> Aug 13 06:35:05 oberon kernel: kernel BUG at include/linux/page-flags.h:814!
> Aug 13 06:35:05 oberon kernel: invalid opcode: 0000 [#1] PREEMPT_RT SMP PTI
> Aug 13 06:35:05 oberon kernel: CPU: 3 PID: 12345 Comm: hackbench Not tainted 5.14.0-rc5-rt8+ #12
> Aug 13 06:35:05 oberon kernel: Hardware name:  /NUC5i7RYB, BIOS RYBDWi35.86A.0359.2016.0906.1028 09/06/2016
> Aug 13 06:35:05 oberon kernel: RIP: 0010:___slab_alloc+0x340/0x940

Are you able to translate this RIP via addr2line?

> Aug 13 06:35:05 oberon kernel: Code: c6 48 0f a3 05 b1 7b 57 03 72 99 c7 85 78 ff ff ff ff ff ff ff 48 8b 7d 88 e9 8d fd ff ff 48 c7 c6 50 5a 7c b0 e>
> Aug 13 06:35:05 oberon kernel: RSP: 0018:ffffba1c4a8b7ab0 EFLAGS: 00010293
> Aug 13 06:35:05 oberon kernel: RAX: 0000000000000000 RBX: 0000000000000002 RCX: ffff9bb765118000
> Aug 13 06:35:05 oberon kernel: RDX: 0000000000000000 RSI: ffffffffaf426050 RDI: 00000000ffffffff
> Aug 13 06:35:05 oberon kernel: RBP: ffffba1c4a8b7b70 R08: 0000000000000000 R09: 0000000000000000
> Aug 13 06:35:05 oberon kernel: R10: 0000000000000000 R11: 0000000000000000 R12: ffff9bb7410d3600
> Aug 13 06:35:05 oberon kernel: R13: 0000000000400cc0 R14: 00000000001f7770 R15: ffff9bbe76df7770
> Aug 13 06:35:05 oberon kernel: FS:  00007f474b1be740(0000) GS:ffff9bbe76c00000(0000) knlGS:0000000000000000
> Aug 13 06:35:05 oberon kernel: CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> Aug 13 06:35:05 oberon kernel: CR2: 00007f60c04bdaf8 CR3: 0000000124f3a003 CR4: 00000000003706e0
> Aug 13 06:35:05 oberon kernel: Call Trace:
> Aug 13 06:35:05 oberon kernel:  ? __alloc_skb+0x1db/0x270
> Aug 13 06:35:05 oberon kernel:  ? __alloc_skb+0x1db/0x270
> Aug 13 06:35:05 oberon kernel:  ? kmem_cache_alloc_node+0xa4/0x2b0
> Aug 13 06:35:05 oberon kernel:  kmem_cache_alloc_node+0xa4/0x2b0
> Aug 13 06:35:05 oberon kernel:  __alloc_skb+0x1db/0x270
> Aug 13 06:35:05 oberon kernel:  alloc_skb_with_frags+0x64/0x250
> Aug 13 06:35:05 oberon kernel:  sock_alloc_send_pskb+0x260/0x2b0
> Aug 13 06:35:05 oberon kernel:  ? bpf_lsm_socket_getpeersec_dgram+0xa/0x10
> Aug 13 06:35:05 oberon kernel:  unix_stream_sendmsg+0x27c/0x550
> Aug 13 06:35:05 oberon kernel:  ? unix_seqpacket_recvmsg+0x60/0x60
> Aug 13 06:35:05 oberon kernel:  sock_sendmsg+0xbd/0xd0
> Aug 13 06:35:05 oberon kernel:  sock_write_iter+0xb9/0x120
> Aug 13 06:35:05 oberon kernel:  new_sync_write+0x175/0x200
> Aug 13 06:35:05 oberon kernel:  vfs_write+0x3c4/0x510
> Aug 13 06:35:05 oberon kernel:  ksys_write+0xc9/0x110
> Aug 13 06:35:05 oberon kernel:  do_syscall_64+0x3b/0x90
> Aug 13 06:35:05 oberon kernel:  entry_SYSCALL_64_after_hwframe+0x44/0xae

While SLUB RT rewrite is obvious suspect, could be also a boring slab
misuse (use-after-free etc), wouldn't be the first related to skb's...
If this reproduces well, could you try booting with slub_debug boot
param. Could catch the culprit sooner (but also hide the bug,
unfortunately).

> Aug 13 06:35:05 oberon kernel: RIP: 0033:0x7f474b3a2877
> Aug 13 06:35:05 oberon kernel: Code: 75 05 48 83 c4 58 c3 e8 37 4e ff ff 0f 1f 80 00 00 00 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 01 0>
> Aug 13 06:35:05 oberon kernel: RSP: 002b:00007ffe5e71e7a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> Aug 13 06:35:05 oberon kernel: RAX: ffffffffffffffda RBX: 00000000000003e8 RCX: 00007f474b3a2877
> Aug 13 06:35:05 oberon kernel: RDX: 00000000000003e8 RSI: 00007ffe5e71e7b0 RDI: 0000000000000010
> Aug 13 06:35:05 oberon kernel: RBP: 00007ffe5e71ebf0 R08: 00007ffe5e71e700 R09: 0000000000000000
> Aug 13 06:35:05 oberon kernel: R10: 0000000000000008 R11: 0000000000000246 R12: 00007ffe5e71e7b0
> Aug 13 06:35:05 oberon kernel: R13: 0000000000000008 R14: 0000560b46008210 R15: 0000000000000000
> Aug 13 06:35:05 oberon kernel: Modules linked in: uinput rfcomm snd_seq_dummy snd_hrtimer xt_CHECKSUM xt_MASQUERADE xt_conntrack ipt_REJECT nf_nat_tf>
> Aug 13 06:35:05 oberon kernel:  snd_intel_dspcfg snd_hda_codec mei_hdcp snd_hda_core snd_hwdep cfg80211 snd_seq iTCO_wdt snd_seq_device intel_pmc_bxt>
> Aug 13 06:35:05 oberon kernel: ---[ end trace 0000000000000002 ]---
> Aug 13 06:35:05 oberon kernel: RIP: 0010:___slab_alloc+0x340/0x940
> Aug 13 06:35:05 oberon kernel: Code: c6 48 0f a3 05 b1 7b 57 03 72 99 c7 85 78 ff ff ff ff ff ff ff 48 8b 7d 88 e9 8d fd ff ff 48 c7 c6 50 5a 7c b0 e>
> Aug 13 06:35:05 oberon kernel: RSP: 0018:ffffba1c4a8b7ab0 EFLAGS: 00010293
> Aug 13 06:35:05 oberon kernel: RAX: 0000000000000000 RBX: 0000000000000002 RCX: ffff9bb765118000
> Aug 13 06:35:05 oberon kernel: RDX: 0000000000000000 RSI: ffffffffaf426050 RDI: 00000000ffffffff
> Aug 13 06:35:05 oberon kernel: RBP: ffffba1c4a8b7b70 R08: 0000000000000000 R09: 0000000000000000
> Aug 13 06:35:05 oberon kernel: R10: 0000000000000000 R11: 0000000000000000 R12: ffff9bb7410d3600
> Aug 13 06:35:05 oberon kernel: R13: 0000000000400cc0 R14: 00000000001f7770 R15: ffff9bbe76df7770
> Aug 13 06:35:05 oberon kernel: FS:  00007f474b1be740(0000) GS:ffff9bbe76c00000(0000) knlGS:0000000000000000
> Aug 13 06:35:05 oberon kernel: CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> Aug 13 06:35:05 oberon kernel: CR2: 00007f60c1d901a0 CR3: 0000000124f3a003 CR4: 00000000003706e0
> Aug 13 06:35:05 oberon kernel: Kernel panic - not syncing:
> 
> Config is attached. 
> 
> I was running the rteval script that kicks off parallel kernel builds and hackbench runs as loads and runs cyclictest with a thread on each core:
> 
> $ sudo rteval --duration=10m
> 
> Clark
>