[systemd-devel] xorg uses 100% CPU after upgrading to 226

[Jin Liu]

According to strace -p, xorg is spinning on a select(), which always return
the same fd #6, which seems related to the system dbus:


$ pgrep Xorg
614
$ strace -p 614
Process 614 attached
select(256, [1 3 5 6 8 10 19 23 25 29 36 37 38 39 40 41], NULL, NULL, {214,
537000}) = 1 (in [6], left {214, 536993})
select(256, [1 3 5 6 8 10 19 23 25 29 36 37 38 39 40 41], NULL, NULL, {214,
537000}) = 1 (in [6], left {214, 536995})
select(256, [1 3 5 6 8 10 19 23 25 29 36 37 38 39 40 41], NULL, NULL, {214,
537000}) = 1 (in [6], left {214, 536995})
select(256, [1 3 5 6 8 10 19 23 25 29 36 37 38 39 40 41], NULL, NULL, {214,
537000}) = 1 (in [6], left {214, 536995})
select(256, [1 3 5 6 8 10 19 23 25 29 36 37 38 39 40 41], NULL, NULL, {214,
537000}) = 1 (in [6], left {214, 536996})
select(256, [1 3 5 6 8 10 19 23 25 29 36 37 38 39 40 41], NULL, NULL, {214,
536000}) = 1 (in [6], left {214, 535996})
select(256, [1 3 5 6 8 10 19 23 25 29 36 37 38 39 40 41], NULL, NULL, {214,
536000}) = 1 (in [6], left {214, 535996})
^C
$ gdb -p 614
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Attaching to process 614
Reading symbols from /usr/lib/xorg-server/Xorg...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libdbus-1.so.3...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libudev.so.1...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libgcrypt.so.20...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libdl.so.2...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libunwind.so.8...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libpciaccess.so.0...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libdrm.so.2...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libpixman-1.so.0...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libXfont.so.1...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libXau.so.6...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libsystemd.so.0...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libxshmfence.so.1...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libXdmcp.so.6...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libm.so.6...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libc.so.6...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libpthread.so.0...(no debugging symbols
found)...done.
[New LWP 980]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/usr/lib/libthread_db.so.1".
Reading symbols from /usr/lib/librt.so.1...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libresolv.so.2...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libcap.so.2...(no debugging symbols
found)...done.
Reading symbols from /lib64/ld-linux-x86-64.so.2...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libgpg-error.so.0...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/liblzma.so.5...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libfreetype.so.6...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libz.so.1...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libfontenc.so.1...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/liblz4.so.1...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libattr.so.1...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libbz2.so.1.0...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libpng16.so.16...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libharfbuzz.so.0...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libglib-2.0.so.0...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libgraphite2.so.3...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libpcre.so.1...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/xorg/modules/extensions/libglx.so...(no
debugging symbols found)...done.
Reading symbols from /usr/lib/libGL.so.1...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libexpat.so.1...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libglapi.so.0...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libXext.so.6...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libXdamage.so.1...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libXfixes.so.3...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libX11-xcb.so.1...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libX11.so.6...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libxcb-glx.so.0...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libxcb-dri2.so.0...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libxcb-dri3.so.0...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libxcb-present.so.0...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libxcb-randr.so.0...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libxcb-xfixes.so.0...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libxcb-render.so.0...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libxcb-shape.so.0...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libxcb-sync.so.1...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libxcb.so.1...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libXxf86vm.so.1...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/xorg/modules/drivers/intel_drv.so...(no
debugging symbols found)...done.
Reading symbols from /usr/lib/libdrm_intel.so.1...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libstdc++.so.6...done.
Reading symbols from /usr/lib/libgcc_s.so.1...done.
Reading symbols from /usr/lib/xorg/modules/input/evdev_drv.so...(no
debugging symbols found)...done.
Reading symbols from /usr/lib/libmtdev.so.1...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libevdev.so.2...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/xorg/modules/input/synaptics_drv.so...(no
debugging symbols found)...done.
Reading symbols from /usr/lib/xorg/modules/dri/i965_dri.so...(no debugging
symbols found)...done.
Reading symbols from /usr/lib/libdrm_nouveau.so.2...(no debugging symbols
found)...done.
Reading symbols from /usr/lib/libdrm_radeon.so.1...(no debugging symbols
found)...done.
0x00007f47ceec8e23 in select () from /usr/lib/libc.so.6
(gdb) bt
#0  0x00007f47ceec8e23 in select () from /usr/lib/libc.so.6
#1  0x000000000058f537 in WaitForSomething ()
#2  0x0000000000438be1 in ?? ()
#3  0x000000000043cf0b in ?? ()
#4  0x00007f47cee07610 in __libc_start_main () from /usr/lib/libc.so.6
#5  0x0000000000427319 in _start ()
(gdb) quit
A debugging session is active.

Inferior 1 [process 614] will be detached.

Quit anyway? (y or n) Y
Detaching from program: /usr/lib/xorg-server/Xorg, process 614
$ ls -l /proc/614/fd/6
lrwx------ 1 jin users 64 9月  23 14:23 /proc/614/fd/6 -> socket:[15637]
$ lsof +E -p 614 | grep 15637
dbus-daem  449 dbus   16u     unix 0xffff8800d8c4e300      0t0   14185
/run/dbus/system_bus_socket type=STREAM ->INO=15637 614,Xorg,6u
Xorg       614  jin    6u     unix 0xffff8800d8c4e680      0t0   15637
type=STREAM ->INO=14185 449,dbus-daem,16u


BTW, I run xorg from a user session, not the usual root.
My software versions:
  systemd / libsystemd 226
  dbus / libdbus 1.10.0-3
  xorg-server 1.17.2-4

On Wed, Sep 23, 2015 at 7:25 AM David Herrmann <dh.herrmann at gmail.com>
wrote:

> Hi
>
> On Tue, Sep 22, 2015 at 9:23 PM, Jin Liu <m.liu.jin at gmail.com> wrote:
> > After upgrading to 226, the Xorg process keeps using 100% CPU. Also, the
> > "xrandr --dpi 168" command in my .xinitrc no longer works.
> >
> > My startx.service and .xinitrc:
> >
> > $ systemctl cat startx.service
> > # /etc/systemd/system/startx.service
> > [Unit]
> > Description=Direct X login
> > After=systemd-user-sessions.service
> > Conflicts=getty at tty1.service
> >
> > [Service]
> > User=jin
> > TTYPath=/dev/tty1
> > PAMName=login
> > Environment=DISPLAY=:0
> > ExecStart=/usr/bin/bash --login -c "cd; (/usr/lib/xorg-server/Xorg
> -nolisten
> > tcp vt1 &); source .xinitrc"
> >
> > [Install]
> > WantedBy=graphical.target
> > $ cat .xinitrc
> > #!/bin/sh
> > #
> > # ~/.xinitrc
> > #
> > # Executed by startx (run your window manager from here)
> >
> > export DESKTOP_SESSION="plasma"
> >
> > if [ -d /etc/X11/xinit/xinitrc.d ]; then
> >  for f in /etc/X11/xinit/xinitrc.d/*; do
> >    [ -x "$f" ] && . "$f"
> >  done
> >  unset f
> > fi
> >
> > xrandr --dpi 168
> >
> > exec /usr/bin/startkde
> >
> > $
> >
> > BTW, if I move the "xrandr --dpi 168" line into /usr/bin/startkde, it
> works
> > again (only DPI setting. Xorg still uses 100% CPU).
> >
> > What change in version 226 could cause the above problem, and how should
> I
> > change the above files to fix it? Thanks.
>
> Please run "strace -p <pid>" on the offending process or "perf top".
> Then try to figure out which function is spinning.
>
> Thanks
> David
>
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