Package: src:linux
Version: 4.9.210-1
Severity: normal
Dear Maintainer,
I performed umount on my system and it got stuck.
Investigation findings:
* umount was stuck in D state
* after two minutes, there was a kernel message - "umount blocked for 120
seconds"
* the process that caused the umount to stuck was:
- running on an isolated CPU (no other processes were running on that CPU)
- running in real time priority (SCHED_FIFO)
- running from root
I managed to create an easy reproduction:
* created and mounted a loopback filesystem as follows:
dd if=/dev/zero of=foodisk bs=1M count=10
mkfs.ext4 foodisk
mkdir foodir
mount foodisk foodir
* compiled & run the attached program
* performed "umount foodir"
* wait...
* when program is killed, umount is released
Note - when trying to reproduce without the syslog call, issue didn't
reproduce. I don't understand the correlation.
Thanks,
Roi
-- Package-specific info:
** Version:
Linux version 4.9.0-12-amd64 (debian-ker...@lists.debian.org) (gcc version
6.3.0 20170516 (Debian 6.3.0-18+deb9u1) ) #1 SMP Debian 4.9.210-1 (2020-01-20)
** Command line:
BOOT_IMAGE=/vmlinuz ro isolcpus=3 quiet init=/bin/systemd
systemd.sysv_console=true systemd.show_status=yes
** Tainted: O (4096)
* Out-of-tree module has been loaded.
** Kernel log:
[ 108.864321] EXT4-fs (loop0): mounted filesystem with ordered data mode.
Opts: (null)
[ 364.235368] INFO: task umount:1302 blocked for more than 120 seconds.
[ 364.236530] Tainted: G O 4.9.0-12-amd64 #1 Debian
4.9.210-1
[ 364.237682] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this
message.
[ 364.238842] umount D 0 1302 1267 0x00000000
[ 364.238850] 0000000000000086 ffff8e9ab1e57400 0000000000000000
ffff8e8ab47f8140
[ 364.238855] ffff8e8abf218980 ffffffff85e11500 ffffb964ce97bc90
ffffffff858193f9
[ 364.238860] ffff8e8abf7989e8 00ffb964ce97bcc0 ffff8e8abf218980
000000000000732a
[ 364.238865] Call Trace:
[ 364.238877] [<ffffffff858193f9>] ? __schedule+0x239/0x6f0
[ 364.238881] [<ffffffff858198e2>] ? schedule+0x32/0x80
[ 364.238885] [<ffffffff8581cc7d>] ? schedule_timeout+0x1dd/0x380
[ 364.238890] [<ffffffff852b4a22>] ? enqueue_task_fair+0x82/0x940
[ 364.238894] [<ffffffff8581a321>] ? wait_for_completion+0xf1/0x130
[ 364.238899] [<ffffffff852a72d0>] ? wake_up_q+0x70/0x70
[ 364.238906] [<ffffffff852968fe>] ? flush_work+0x10e/0x1c0
[ 364.238910] [<ffffffff85292e60>] ? destroy_worker+0x80/0x80
[ 364.238916] [<ffffffff853970dd>] ? lru_add_drain_all+0x11d/0x160
[ 364.238925] [<ffffffff854497a1>] ? invalidate_bdev+0x21/0x40
[ 364.238973] [<ffffffffc02c755b>] ? ext4_put_super+0x1fb/0x3a0 [ext4]
[ 364.238980] [<ffffffff8540ff6c>] ? generic_shutdown_super+0x6c/0xf0
[ 364.238984] [<ffffffff854102d1>] ? kill_block_super+0x21/0x60
[ 364.238988] [<ffffffff854103da>] ? deactivate_locked_super+0x3a/0x70
[ 364.238993] [<ffffffff8542f4fb>] ? cleanup_mnt+0x3b/0x80
[ 364.238998] [<ffffffff8529a2bf>] ? task_work_run+0x7f/0xa0
[ 364.239003] [<ffffffff85203754>] ? exit_to_usermode_loop+0xa4/0xb0
[ 364.239007] [<ffffffff85203bd9>] ? do_syscall_64+0xe9/0x100
[ 364.239011] [<ffffffff8581e1ce>] ? entry_SYSCALL_64_after_swapgs+0x58/0xc6
** Model information
sys_vendor: Intel Corporation
product_name: S2600WT2R
product_version: ....................
chassis_vendor: ...............................
chassis_version: ..................
bios_vendor: Intel Corporation
bios_version: SE5C610.86B.01.01.0016.C5.033120161139
board_vendor: Intel Corporation
board_name: S2600WT2R
board_version: H21573-365
** USB devices:
not available
-- System Information:
Debian Release: 9.12
APT prefers oldstable-updates
APT policy: (500, 'oldstable-updates'), (500, 'oldstable')
Architecture: amd64 (x86_64)
Kernel: Linux 4.9.0-12-amd64 (SMP w/88 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8),
LANGUAGE=en_US:en (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
Versions of packages linux-image-4.9.0-12-amd64 depends on:
ii initramfs-tools [linux-initramfs-tool] 0.130
ii kmod 23-2
ii linux-base 4.5
Versions of packages linux-image-4.9.0-12-amd64 recommends:
pn firmware-linux-free <none>
pn irqbalance <none>
Versions of packages linux-image-4.9.0-12-amd64 suggests:
pn debian-kernel-handbook <none>
ii grub-pc 2.02~beta3-5+deb9u2
pn linux-doc-4.9 <none>
Versions of packages linux-image-4.9.0-12-amd64 is related to:
pn firmware-amd-graphics <none>
pn firmware-atheros <none>
pn firmware-bnx2 <none>
pn firmware-bnx2x <none>
pn firmware-brcm80211 <none>
pn firmware-cavium <none>
pn firmware-intel-sound <none>
pn firmware-intelwimax <none>
pn firmware-ipw2x00 <none>
pn firmware-ivtv <none>
pn firmware-iwlwifi <none>
pn firmware-libertas <none>
pn firmware-linux-nonfree <none>
pn firmware-misc-nonfree <none>
pn firmware-myricom <none>
pn firmware-netxen <none>
pn firmware-qlogic <none>
pn firmware-realtek <none>
pn firmware-samsung <none>
pn firmware-siano <none>
pn firmware-ti-connectivity <none>
pn xen-hypervisor <none>
-- no debconf information
#include <iostream>
#include <sched.h>
#include <syslog.h>
using namespace std;
static const int isolCpuNum = 3;
int main() {
cout << "Starting do_nothing..." << endl;
pid_t pid = 0;
cpu_set_t mask;
CPU_ZERO(&mask);
CPU_SET(isolCpuNum, &mask);
size_t cpusetsize = sizeof(mask);
sched_setaffinity(pid, cpusetsize, &mask);
int policy = SCHED_FIFO;
sched_param param;
param.sched_priority = 90;
int ret_val = sched_setscheduler(pid, policy, ¶m);
cout << "sched_setscheduler ret_val: " << ret_val << endl;
syslog(LOG_NOTICE, "Hello World from do_nothing");
int count = 0;
while (true) {
if (count == 50000)
count = 0;
count++;
}
return 0;
}
