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Bug 2092322 - [QSD] pid file still exist after qsd process be killed when qsd run as daemonize
Summary: [QSD] pid file still exist after qsd process be killed when qsd run as daemonize
Keywords:
Status: CLOSED CURRENTRELEASE
Alias: None
Product: Red Hat Enterprise Linux 9
Classification: Red Hat
Component: qemu-kvm
Version: 9.1
Hardware: All
OS: Linux
low
low
Target Milestone: rc
: ---
Assignee: Hanna Czenczek
QA Contact: qing.wang
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2022-06-01 09:34 UTC by qing.wang
Modified: 2022-12-21 08:33 UTC (History)
8 users (show)

Fixed In Version:
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
Environment:
Last Closed: 2022-12-21 08:33:47 UTC
Type: ---
Target Upstream Version:
Embargoed:

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System ID Private Priority Status Summary Last Updated
Red Hat Issue Tracker RHELPLAN-123867 0 None None None 2022-06-01 09:44:57 UTC

Description qing.wang 2022-06-01 09:34:17 UTC 
Description of problem:
run qsd with pidfile and daemonize options. the pid file still exist after qsd process be killed.

Version-Release number of selected component (if applicable):
Red Hat Enterprise Linux release 9.1 Beta (Plow)
5.14.0-101.el9.x86_64
qemu-kvm-7.0.0-4.el9.x86_64
seabios-bin-1.16.0-3.el9.noarch
edk2-ovmf-20220221gitb24306f15d-2.el9.noarch
virtio-win-prewhql-0.1-221.iso


How reproducible:
100

Steps to Reproduce:
1.boot qsd with pidfile and daemonize options
qemu-storage-daemon \
--chardev socket,path=qmp.sock,server=on,wait=off,id=char1 \
--monitor chardev=char1 \
--pidfile qsd.pid \
--daemonize \

2.check the process
pgrep  -l -x -F qsd.pid|grep qemu-storage-da

3.kill process
kill  -SIGTERM $(<qsd.pid)

4.check the process
pgrep -l -x qemu-storage-da

5.check the pid file


Actual results:
pif file qsd.pid still exist on disk

Expected results:
This file should be deleted after qsd process quit.

Additional info:
It meet expected result if run without daemonize
Comment 2 Hanna Czenczek 2022-06-09 07:40:58 UTC 
The problem is that daemonizing changes the current working directory to /, so the PID file cannot be removed if it was specified by relative path.  This is also true for qemu itself:

$ pwd
/tmp
$ qemu-system-x86_64 --daemonize --pidfile qemu.pid
$ kill $(cat qemu.pid)
$ ls -l qemu.pid
-rw------- 1 hreitz users 6  9. Jun 09:38 qemu.pid

We should probably always expand the PID file path to absolute paths internally.
Comment 3 qing.wang 2022-07-07 01:35:09 UTC 
It still exist even using absolute paths on
Red Hat Enterprise Linux release 9.0 (Plow)
5.14.0-70.15.1.el9_0.x86_64
qemu-kvm-7.0.0-7.el9.x86_64
seabios-bin-1.15.0-1.el9.noarch
edk2-ovmf-20220126gitbb1bba3d77-3.el9.noarch




root@dell-per6515-03 /home $ qemu-storage-daemon --daemonize --pidfile /tmp/qemu.pid
root@dell-per6515-03 /home $  ps -e ww|grep qemu-storage-daemon|grep -v grep
 208762 ?        Sl     0:00 qemu-storage-daemon --daemonize --pidfile /tmp/qemu.pid
root@dell-per6515-03 /home $ kill -9 208762
root@dell-per6515-03 /home $ ls /tmp/qemu.pid 
/tmp/qemu.pid
Comment 4 Hanna Czenczek 2022-07-07 07:01:36 UTC 
(In reply to qing.wang from comment #3)
> root@dell-per6515-03 /home $ qemu-storage-daemon --daemonize --pidfile
> /tmp/qemu.pid
> root@dell-per6515-03 /home $  ps -e ww|grep qemu-storage-daemon|grep -v grep
>  208762 ?        Sl     0:00 qemu-storage-daemon --daemonize --pidfile
> /tmp/qemu.pid
> root@dell-per6515-03 /home $ kill -9 208762

If you kill the process via SIGKILL, it has no chance to delete the PID file.  This should be the case with or without --daemonize.

The PID file can only be deleted if the process is terminated such that atexit() handlers run, e.g. via SIGTERM (as done in comment 0) or SIGINT.

Hanna
Comment 5 qing.wang 2022-07-11 07:58:41 UTC 
verify on qemu-kvm-7.0.0-8.el9.x86_64:

1.qemu-storage-daemon --daemonize --pidfile /tmp/qemu.pid
2.kill  -SIGTERM $(cat /tmp/qemu.pid)
3. ps -e ww|grep qemu-storage-daemon|grep -v grep
4. ls /tmp/qemu.pid
ls: cannot access '/tmp/qemu.pid': No such file or director

It get expected result.
I suggest adding this to document or help message.
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