Re: [PATCH 5.15 00/92] 5.15.126-rc1 review

[Guenter Roeck]

On Wed, Aug 09, 2023 at 02:35:59PM -0400, Joel Fernandes wrote:
> On Wed, Aug 9, 2023 at 12:18 PM Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
> >
> > On 8/9/23 06:53, Joel Fernandes wrote:
> > > On Wed, Aug 09, 2023 at 12:40:36PM +0200, Greg Kroah-Hartman wrote:
> > >> This is the start of the stable review cycle for the 5.15.126 release.
> > >> There are 92 patches in this series, all will be posted as a response
> > >> to this one.  If anyone has any issues with these being applied, please
> > >> let me know.
> > >>
> > >> Responses should be made by Fri, 11 Aug 2023 10:36:10 +0000.
> > >> Anything received after that time might be too late.
> > >>
> > >> The whole patch series can be found in one patch at:
> > >>      https://www.kernel.org/pub/linux/kernel/v5.x/stable-review/patch-5.15.126-rc1.gz
> > >> or in the git tree and branch at:
> > >>      git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git linux-5.15.y
> > >> and the diffstat can be found below.
> > >
> > > Not necesscarily new with 5.15 stable but 3 of the 19 rcutorture scenarios
> > > hang with this -rc: TREE04, TREE07, TASKS03.
> > >
> > > 5.15 has a known stop machine issue where it hangs after 1.5 hours with cpu
> > > hotplug rcutorture testing. Me and tglx are continuing to debug this. The
> > > issue does not show up on anything but 5.15 stable kernels and neither on
> > > mainline.
> > >
> >
> > Do you by any have a crash pattern that we could possibly use to find the crash
> > in ChromeOS crash logs ? No idea if that would help, but it could provide some
> > additional data points.
> 
> The pattern shows as a hard hang, the system is unresponsive and all CPUs
> are stuck in stop_machine. Sometimes it recovers on its own from the
> hang and then RCU immediately gives stall warnings. It takes 1.5 hour
> to reproduce and sometimes never happens for several hours.
> 
> It appears related to CPU hotplug since gdb showed me most of the CPUs
> are spinning in multi_cpu_stop() / stop machine after the hang.
> 

Hmm, we do see lots of soft lockups with multi_cpu_stop() in the backtrace,
but not with v5.15.y but with v5.4.y. The actual hang is in stop_machine_yield().
Example:

<0>[63298.624328] watchdog: BUG: soft lockup - CPU#0 stuck for 11s! [migration/0:11]
<4>[63298.624331] Modules linked in: 8021q ccm snd_seq_dummy snd_seq snd_seq_device bridge stp llc tun nf_nat_tftp nf_conntrack_tftp nf_nat_ftp nf_conntrack_ftp esp6 ah6 ip6t_REJECT ip6t_ipv6header vhost_vsock vhost vmw_vsock_virtio_transport_common vsock veth rfcomm xt_cgroup cmac algif_hash algif_skcipher af_alg xt_MASQUERADE uinput iwlmvm snd_soc_skl_ssp_clk iwl7000_mac80211 btusb snd_soc_kbl_da7219_max98357a btrtl btintel snd_soc_hdac_hdmi btbcm bluetooth snd_soc_dmic snd_soc_skl ecdh_generic ecc snd_soc_sst_ipc snd_soc_sst_dsp snd_soc_hdac_hda uvcvideo snd_soc_acpi_intel_match snd_soc_acpi snd_hda_ext_core videobuf2_vmalloc videobuf2_v4l2 videobuf2_common snd_intel_dspcfg videobuf2_memops snd_hda_codec snd_hwdep snd_hda_core iwlwifi snd_soc_da7219 snd_soc_max98357a fuse ip6table_nat cfg80211 lzo_rle lzo_compress zram joydev
<4>[63298.624357] CPU: 0 PID: 11 Comm: migration/0 Tainted: G     U  W         5.4.180-17902-g44152654f29b #1
<4>[63298.624358] Hardware name: Google Nami/Nami, BIOS Google_Nami.10775.145.0 09/19/2019
<4>[63298.624363] RIP: 0010:stop_machine_yield+0xb/0xd
<4>[63298.624366] Code: ff 74 b6 f0 ff 0f 75 b1 48 83 c7 08 e8 1f cb f9 ff eb a6 e8 a0 20 e3 ff eb bc e8 50 4b f5 ff 0f 1f 44 00 00 55 48 89 e5 f3 90 <5d> c3 0f 1f 44 00 00 55 48 89 e5 41 57 41 56 41 55 41 54 53 48 81
<4>[63298.624368] RSP: 0000:ffffbaf90006fe38 EFLAGS: 00000293 ORIG_RAX: ffffffffffffff13
<4>[63298.624370] RAX: 0000000000000000 RBX: ffffbaf90300bca8 RCX: 0000000000000000
<4>[63298.624371] RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffffb0d46920
<4>[63298.624373] RBP: ffffbaf90006fe38 R08: 0000000000000002 R09: 0000398ecf9a0ac5
<4>[63298.624374] R10: 0000000000000171 R11: ffffffffaf9cfb11 R12: 0000000000000001
<4>[63298.624376] R13: ffff9b09baa22201 R14: ffffffffb0d46920 R15: 0000000000000001
<4>[63298.624377] FS:  0000000000000000(0000) GS:ffff9b09baa00000(0000) knlGS:0000000000000000
<4>[63298.624379] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
<4>[63298.624380] CR2: 0000153c00724820 CR3: 0000000171ab8005 CR4: 00000000003606f0
<4>[63298.624382] Call Trace:
<4>[63298.624386]  multi_cpu_stop+0x89/0x119
<4>[63298.624389]  ? stop_two_cpus+0x24d/0x24d
<4>[63298.624391]  cpu_stopper_thread+0x8f/0x111
<4>[63298.624394]  smpboot_thread_fn+0x174/0x212
<4>[63298.624397]  kthread+0x147/0x156
<4>[63298.624399]  ? cpu_report_death+0x43/0x43
<4>[63298.624401]  ? kthread_blkcg+0x2e/0x2e
<4>[63298.624404]  ret_from_fork+0x35/0x40
<0>[63298.624407] Kernel panic - not syncing: softlockup: hung tasks

I guess that is something different ?

Guenter