/usr/lib/cups/backend/hp eats 100% CPU cloning processes

[Alexey Khoroshilov]

Probably after turning off Hewlett-Packard-HP_LaserJet_Professional_P_1102w, while there is an active print job , I got /usr/lib/cups/backend/hp eating 100% CPU.

strace shows the following cycle:
[pid 5886] +++ exited with 0 +++
[pid 5887] set_robust_list(0x7f6c2e7fc9e0, 24) = 0
[pid 22792] <... clone resumed> child_stack=0x7f6c2e7fbfb0, flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SYSVSEM|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID, parent_tidptr=0x7f6c2e7fc9d0, tls=0x7f6c2e7fc700, child_tidptr=0x7f6c2e7fc9d0) = 5887
[pid 22792] futex(0x7f6c373f06dc, FUTEX_WAIT_BITSET_PRIVATE|FUTEX_CLOCK_REALTIME, 1645005345, {1417641070, 28878000}, ffffffff <unfinished ...>
[pid 5887] timerfd_settime(13, TFD_TIMER_ABSTIME, {it_interval={0, 0}, it_value={385967, 675423000}}, NULL) = 0
[pid 5887] ioctl(14, USBDEVFS_SUBMITURB, 0x7f6c30000b50) = -1 ENODEV (No such device)
[pid 5887] timerfd_settime(13, 0, {it_interval={0, 0}, it_value={0, 0}}, NULL) = 0
[pid 5887] futex(0x7f6c373f06dc, FUTEX_WAKE_OP_PRIVATE, 1, 1, 0x7f6c373f06d8, {FUTEX_OP_SET, 0, FUTEX_OP_CMP_GT, 1}) = 1
[pid 22792] <... futex resumed> ) = 0
[pid 5887] madvise(0x7f6c2dffc000, 8368128, MADV_DONTNEED <unfinished ...>
[pid 22792] futex(0x7f6c373f06b0, FUTEX_WAKE_PRIVATE, 1 <unfinished ...>
[pid 5887] <... madvise resumed> ) = 0
[pid 22792] <... futex resumed> ) = 0
[pid 5887] _exit(0) = ?
[pid 22792] clone(Process 5888 attached
 <unfinished ...>
[pid 5887] +++ exited with 0 +++
[pid 5888] set_robust_list(0x7f6c2f7fe9e0, 24) = 0

So it seems pthread is constantly created and finished.

Relevant messages from syslog:
Dec 3 08:45:50 kernel: [105012.797064] usblp0: removed
Dec 3 08:45:51 hp[22792]: prnt/backend/hp.c 371: read new pjl status: 10023
Dec 3 08:46:04 kernel: [105026.779759] usb 1-1.2: USB disconnect, device number 12
Dec 3 08:46:04 udev-configure-printer: remove /devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2
Dec 3 08:46:04 colord: device removed: sysfs-Hewlett-Packard-HP_LaserJet_Professional_P_1102w
Dec 3 08:46:21 kernel: [105044.131029] usb 1-1.2: new high-speed USB device number 13 using ehci-pci
Dec 3 08:46:21 kernel: [105044.224815] usb 1-1.2: New USB device found, idVendor=03f0, idProduct=102a
Dec 3 08:46:21 kernel: [105044.224823] usb 1-1.2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
Dec 3 08:46:21 kernel: [105044.224827] usb 1-1.2: Product: HP LaserJet Professional P 1102w
Dec 3 08:46:21 kernel: [105044.224830] usb 1-1.2: Manufacturer: Hewlett-Packard
Dec 3 08:46:21 kernel: [105044.224833] usb 1-1.2: SerialNumber: 000000000W40143EPR1a
Dec 3 08:46:21 kernel: [105044.227663] usblp 1-1.2:1.0: usblp0: USB Bidirectional printer dev 13 if 0 alt 0 proto 2 vid 0x03F0 pid 0x102A
Dec 3 08:46:21 logger: loading HP Device 001 013
Dec 3 08:46:21 colord: Device added: sysfs-Hewlett-Packard-HP_LaserJet_Professional_P_1102w

> dpkg -s hplip
Package: hplip
Status: install ok installed
Priority: optional
Section: utils
Installed-Size: 394
Maintainer: Ubuntu Developers <email address hidden>
Architecture: amd64
Version: 3.14.3-0ubuntu3.2

[Launchpad Janitor (janitor)]

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