ps hangs when listing root processes

[3depict]

when running "ps a" on my system, the command just blocks, and will not respond to Ctrl+C, nor killall -9 ps.

This also happens in gnome-system-monitor, if and only if viewing all processes (not just "my processes").

Strace output attached. Curiously, I can cancel out with Ctrl+C if using the strace wrapped process.

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: procps 1:3.2.8-10ubuntu5
ProcVersionSignature: Ubuntu 3.0.0-12.20-generic 3.0.4
Uname: Linux 3.0.0-12-generic x86_64
ApportVersion: 1.23-0ubuntu3
Architecture: amd64
Date: Sat Dec 31 02:22:15 2011
InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Release amd64 (20111012)
SourcePackage: procps
UpgradeStatus: No upgrade log present (probably fresh install)
mtime.conffile..etc.sysctl.conf: 2011-12-21T19:15:22.651303

[3depict (tehuser)]

Oh, additonal comment - this is a virtual machine running in VirtualBox 3.2.6

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Michael Burge (michaelburge)]

I'm getting this also. I have a Skype instance that doesn't terminate when closed, but otherwise appears to function normally. When I list all processes with "ps -ax", it hangs and can't be killed.

[drink (martin-espinoza)]

I'm having this problem on latest Quantal.
ps works, ps a or ps x hangs
top works fine

[Hans Deragon (deragon)]

Currently have this problem on 12.04 when running as root and running 'ps -ef'. 'ps' alone works. 'top' works. Below, the output of strace where it hangs. Seams that the problem is Xorg in my case. I just switch my computer to the proprietary ATI driver. Still, regardless of what is running, ps (or the underlining /proc) should never hang. I tried the following and it hangs too. <CTRL-C> does not help.

# cat /proc/1899/cmdline

strace of ps:

[... deleted lines ...]
write(1, "bind 1881 1 0 07:35 ? "..., 72bind 1881 1 0 07:35 ? 00:00:00 /usr/sbin/named -u bind
) = 72
stat("/proc/1899", {st_mode=S_IFDIR|0555, st_size=0, ...}) = 0
open("/proc/1899/stat", O_RDONLY) = 6
read(6, "1899 (Xorg) D 1867 1899 1899 103"..., 1023) = 380
close(6) = 0
open("/proc/1899/status", O_RDONLY) = 6
read(6, "Name:\tXorg\nState:\tD (disk sleep)"..., 1023) = 763
close(6) = 0
open("/proc/1899/cmdline", O_RDONLY) = 6
read(6,

[Lorrin Nelson (lhn-g)]

I just upgraded from 16.04 (via >16.10) to 17.04 and now I'm seeing this too. I tried the strace and observed that ps was hanging trying to list the commandline of the thunderbird process. I had already exited Thunderbird and there were no indications in the GUI that it was still running. I had no luck getting rid of the process with kill -9. Also I could not shut the machine down cleanly. I did findi a bunch of NMI watchdog: BUG: soft lockup messages in syslog, which I'll attach to the bug report.

[Lorrin Nelson (lhn-g)]

Apr 20 08:21:23 gooseberry kernel: [41066.028367] NMI watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [JS Helper:5435]
Apr 20 08:21:23 gooseberry kernel: [41066.028370] Modules linked in: rfcomm pci_stub vboxpci(OE) vboxnetadp(OE) vboxnetflt(OE) vboxdrv(OE) bnep binfmt_misc snd_hda_codec_hdmi zfs(PO) zunicode(PO) zavl(PO) zcommon(PO) znvpair(PO) spl(O) dm_crypt input_leds nvidia_uvm(POE) snd_usb_audio eeepc_wmi asus_wmi snd_usbmidi_lib sparse_keymap video mxm_wmi joydev btusb btrtl btbcm btintel bluetooth intel_rapl x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm irqbypass crct10dif_pclmul snd_hda_codec_realtek crc32_pclmul snd_hda_codec_generic ghash_clmulni_intel pcbc snd_hda_intel snd_hda_codec snd_hda_core snd_hwdep aesni_intel snd_pcm aes_x86_64 crypto_simd glue_helper cryptd snd_seq_midi snd_seq_midi_event nvidia(POE) intel_cstate snd_rawmidi intel_rapl_perf snd_seq lpc_ich snd_seq_device snd_timer snd drm soundcore mei_me mei shpchp
Apr 20 08:21:23 gooseberry kernel: [41066.028399] mac_hid wmi cuse parport_pc ppdev sunrpc lp parport ip_tables x_tables autofs4 wacom hid_generic usbhid hid firewire_ohci e1000e firewire_core ahci crc_itu_t libahci ptp pps_core fjes
Apr 20 08:21:23 gooseberry kernel: [41066.028418] CPU: 0 PID: 5435 Comm: JS Helper Tainted: P D OEL 4.10.0-19-generic #21-Ubuntu
Apr 20 08:21:23 gooseberry kernel: [41066.028419] Hardware name: System manufacturer System Product Name/P8P67 PRO, BIOS 1502 03/02/2011
Apr 20 08:21:23 gooseberry kernel: [41066.028420] task: ffff9881f18eda00 task.stack: ffffaf0343ac4000
Apr 20 08:21:23 gooseberry kernel: [41066.028424] RIP: 0010:native_queued_spin_lock_slowpath+0x12d/0x1a0
Apr 20 08:21:23 gooseberry kernel: [41066.028425] RSP: 0000:ffffaf0343ac7d48 EFLAGS: 00000202 ORIG_RAX: ffffffffffffff10
Apr 20 08:21:23 gooseberry kernel: [41066.028426] RAX: 0000000000000000 RBX: ffffd9b513780a70 RCX: ffff98825f419e40
Apr 20 08:21:23 gooseberry kernel: [41066.028427] RDX: 0000000000180101 RSI: 0000000000000101 RDI: ffffd9b513780a70
Apr 20 08:21:23 gooseberry kernel: [41066.028428] RBP: ffffaf0343ac7d48 R08: 0000000000040000 R09: 0000000000000000
Apr 20 08:21:23 gooseberry kernel: [41066.028429] R10: 001437ee1a0e2cac R11: 00007f58c45f8e60 R12: ffff98811e0297f8
Apr 20 08:21:23 gooseberry kernel: [41066.028429] R13: 3e000000003c18ff R14: ffffaf0343ac7e30 R15: ffff988121b9bc80
Apr 20 08:21:23 gooseberry kernel: [41066.028431] FS: 00007f58c45f9700(0000) GS:ffff98825f400000(0000) knlGS:0000000000000000
Apr 20 08:21:23 gooseberry kernel: [41066.028432] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Apr 20 08:21:23 gooseberry kernel: [41066.028433] CR2: 00007f58a9cffff8 CR3: 00000004de22f000 CR4: 00000000000406f0
Apr 20 08:21:23 gooseberry kernel: [41066.028434] Call Trace:
Apr 20 08:21:23 gooseberry kernel: [41066.028438] _raw_spin_lock+0x20/0x30
Apr 20 08:21:23 gooseberry kernel: [41066.028441] __migration_entry_wait+0x1c/0x180
Apr 20 08:21:23 gooseberry kernel: [41066.028442] migration_entry_wait+0x74/0x80
Apr 20 08:21:23 gooseberry kernel: [41066.028445] do_swap_page+0x5b3/0x770
Apr 20 08:21:23 gooseberry kernel: [41066.028446] ? futex_wake+0x90/0x170
Apr 20 08:21:2...