If Xwayland crashed, you should find a backtrace in journalctl at the time of the crash, can you please post that?

Xwayland not crashed it exit with code 01 as you can see above.
> [Inferior 1 (process 5601) exited with code 01]

But this lead to crash gnome-shell process.
https://bugzilla.gnome.org/page.cgi?id=traceparser/trace.html&trace_id=237973

Thread 1 (Thread 0x7f101a3d2ac0 (LWP 1214)):
#0  0x00007f10195167b1 in _g_log_abort (breakpoint=1) at gmessages.c:554
#1  0x00007f10195177ec in g_log_default_handler (log_domain=<optimized out>, log_level=<optimized out>, message=<optimized out>, unused_data=<optimized out>)
    at gmessages.c:3051
#2  0x00005579cc6d4745 in default_log_handler (log_domain=log_domain@entry=0x7f1017aacf73 "mutter", log_level=log_level@entry=6, message=message@entry=0x5579d110fdb0 "Connection to xwayland lost", data=data@entry=0x0) at ../src/main.c:311
#3  0x00007f1019517a7d in g_logv (log_domain=0x7f1017aacf73 "mutter", log_level=G_LOG_LEVEL_ERROR, format=<optimized out>, args=args@entry=0x7fff4a5d74b0) at gmessages.c:1341
#4  0x00007f1019517bef in g_log (log_domain=log_domain@entry=0x7f1017aacf73 "mutter", log_level=log_level@entry=G_LOG_LEVEL_ERROR, format=format@entry=0x7f1017abf1f0 "Connection to xwayland lost") at gmessages.c:1403
#5  0x00007f1017a6f37e in x_io_error (display=<optimized out>) at wayland/meta-xwayland.c:411
#6  0x00007f101618bede in _XIOError (dpy=dpy@entry=0x5579ce5e8420) at XlibInt.c:1469
#7  0x00007f101618976d in _XEventsQueued (dpy=dpy@entry=0x5579ce5e8420, mode=mode@entry=2) at xcb_io.c:352
#8  0x00007f101617b2bd in XPending (dpy=0x5579ce5e8420) at Pending.c:55
#9  0x00007f1016cdc41e in gdk_check_xpending (display=0x5579ce5f80e0 [GdkX11Display]) at gdkeventsource.c:269
#10 0x00007f1016cdc41e in gdk_event_source_prepare (source=<optimized out>, timeout=timeout@entry=0x7fff4a5d7624) at gdkeventsource.c:287
#11 0x00007f1019510439 in g_main_context_prepare (context=context@entry=0x5579ce2e18c0, priority=priority@entry=0x7fff4a5d76b0) at gmain.c:3450
#12 0x00007f1019510e0b in g_main_context_iterate (context=0x5579ce2e18c0, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at gmain.c:3866
#13 0x00007f1019511272 in g_main_loop_run (loop=0x5579ce5d1d40) at gmain.c:4082
#14 0x00007f1017a3ba6c in meta_run () at core/main.c:648
#15 0x00005579cc6d4277 in main (argc=<optimized out>, argv=<optimized out>) at ../src/main.c:462

> #4  0x00007f1019517bef in g_log (log_domain=log_domain@entry=0x7f1017aacf73 "mutter", log_level=log_level@entry=G_LOG_LEVEL_ERROR, format=format@entry=0x7f1017abf1f0 "Connection to xwayland lost") at gmessages.c:1403

The backtrace in comment 2 is from mutter/gnome-shell losing its connection to the Xserver (Xwayland in this case), it's not a bug in gnome-shell, it's Xwayland vanishing.

Xwayland itself won't exit under normal circumstances, so I believe something wrong happened to Xwayland, it might show (something) in the journactl logs.

I hope you got answer here:

[99333.663897] localhost.localdomain org.gnome.Shell.desktop[1821]: Key repeat discarded, Wayland compositor doesn't seem to be processing events fast enough!
[99333.700841] localhost.localdomain org.gnome.Shell.desktop[1821]: Key repeat discarded, Wayland compositor doesn't seem to be processing events fast enough!
[99333.737579] localhost.localdomain org.gnome.Shell.desktop[1821]: Key repeat discarded, Wayland compositor doesn't seem to be processing events fast enough!
[99333.774870] localhost.localdomain org.gnome.Shell.desktop[1821]: Key repeat discarded, Wayland compositor doesn't seem to be processing events fast enough!
[99333.812243] localhost.localdomain org.gnome.Shell.desktop[1821]: Key repeat discarded, Wayland compositor doesn't seem to be processing events fast enough!
[99333.849728] localhost.localdomain org.gnome.Shell.desktop[1821]: Key repeat discarded, Wayland compositor doesn't seem to be processing events fast enough!
[99333.886684] localhost.localdomain org.gnome.Shell.desktop[1821]: Key repeat discarded, Wayland compositor doesn't seem to be processing events fast enough!
[99333.923310] localhost.localdomain org.gnome.Shell.desktop[1821]: Key repeat discarded, Wayland compositor doesn't seem to be processing events fast enough!
[99333.960973] localhost.localdomain org.gnome.Shell.desktop[1821]: Key repeat discarded, Wayland compositor doesn't seem to be processing events fast enough!
[99333.997842] localhost.localdomain org.gnome.Shell.desktop[1821]: Key repeat discarded, Wayland compositor doesn't seem to be processing events fast enough!
[99334.033116] localhost.localdomain org.gnome.Shell.desktop[1821]: Key repeat discarded, Wayland compositor doesn't seem to be processing events fast enough!
[99334.060056] localhost.localdomain org.gnome.Shell.desktop[1821]: (EE)
[99334.060056] localhost.localdomain org.gnome.Shell.desktop[1821]: Fatal server error:
[99334.060056] localhost.localdomain org.gnome.Shell.desktop[1821]: (EE) Error sending request: Resource temporarily unavailable
[99334.060056] localhost.localdomain org.gnome.Shell.desktop[1821]: (EE)
[99334.119365] localhost.localdomain gsd-clipboard[2028]: gsd-clipboard: Fatal IO error 11 (Resource temporarily unavailable) on X server :0.
[99334.120388] localhost.localdomain gsd-a11y-keyboa[2024]: gsd-a11y-keyboard: Fatal IO error 11 (Resource temporarily unavailable) on X server :0.
[99334.121221] localhost.localdomain sealertauto.desktop[2147]: seapplet: Fatal IO error 11 (Resource temporarily unavailable) on X server :0.
[99334.121970] localhost.localdomain gsd-power[1992]: gsd-power: Fatal IO error 11 (Resource temporarily unavailable) on X server :0.
[99334.134687] localhost.localdomain at-spi-bus-launcher[1850]: XIO:  fatal IO error 11 (Resource temporarily unavailable) on X server ":0"
[99334.134687] localhost.localdomain at-spi-bus-launcher[1850]:       after 83655 requests (83655 known processed) with 0 events remaining.
[99334.137405] localhost.localdomain gsd-media-keys[2037]: gsd-media-keys: Fatal IO error 11 (Resource temporarily unavailable) on X server :0.
[99334.138220] localhost.localdomain gsd-keyboard[2033]: gsd-keyboard: Fatal IO error 11 (Resource temporarily unavailable) on X server :0.
[99334.138974] localhost.localdomain gsd-color[2032]: gsd-color: Fatal IO error 11 (Resource temporarily unavailable) on X server :0.
[99334.139778] localhost.localdomain gsd-xsettings[2011]: gsd-xsettings: Fatal IO error 11 (Resource temporarily unavailable) on X server :0.
[99334.193245] localhost.localdomain gnome-session[1694]: gnome-session-binary[1694]: WARNING: App 'org.gnome.SettingsDaemon.Keyboard.desktop' exited with code 1
[99334.204979] localhost.localdomain gnome-session-binary[1694]: WARNING: App 'org.gnome.SettingsDaemon.Keyboard.desktop' exited with code 1
[99334.228878] localhost.localdomain ibus-daemon[1910]: GChildWatchSource: Exit status of a child process was requested but ECHILD was received by waitpid(). Most likely the process is ignoring SIGCHLD, or some other thread is invoking waitpid() with a nonpositive first argument; either behavior can break applications that use g_child_watch_add()/g_spawn_sync() either directly or indirectly.
[99334.230418] localhost.localdomain bluetoothd[781]: Endpoint unregistered: sender=:1.67 path=/MediaEndpoint/A2DPSource
[99334.231533] localhost.localdomain bluetoothd[781]: Endpoint unregistered: sender=:1.67 path=/MediaEndpoint/A2DPSink
[99334.232152] localhost.localdomain org.gnome.Shell.desktop[1821]: xcb_connection_has_error() returned true
[99334.305815] localhost.localdomain gnome-session[1694]: gnome-session-binary[1694]: WARNING: App 'org.gnome.SettingsDaemon.Clipboard.desktop' exited with code 1
[99334.307541] localhost.localdomain gnome-session-binary[1694]: WARNING: App 'org.gnome.SettingsDaemon.Clipboard.desktop' exited with code 1
[99334.341310] localhost.localdomain gnome-session[1694]: gnome-session-binary[1694]: WARNING: App 'org.gnome.SettingsDaemon.A11yKeyboard.desktop' exited with code 1
[99334.342529] localhost.localdomain gnome-session-binary[1694]: WARNING: App 'org.gnome.SettingsDaemon.A11yKeyboard.desktop' exited with code 1
[99334.364058] localhost.localdomain org.gnome.SettingsDaemon.Keyboard.desktop[1351]: Cannot open display:
[99334.393396] localhost.localdomain gsd-color[1528]: failed to connect to device: Failed to connect to missing device /org/freedesktop/ColorManager/devices/xrandr_Ancor_Communications_Inc_ASUS_ML239_BCLMIB555112_mikhail_1000
[99334.409190] localhost.localdomain org.gnome.SettingsDaemon.Clipboard.desktop[1354]: Cannot open display:
[99334.414772] localhost.localdomain gnome-session[1694]: gnome-session-binary[1694]: WARNING: Child process 2011 was already dead.
[99334.415652] localhost.localdomain gnome-session-binary[1694]: WARNING: Child process 2011 was already dead.
[99334.452167] localhost.localdomain gnome-session[1694]: gnome-session-binary[1694]: WARNING: Child process 2032 was already dead.
[99334.453076] localhost.localdomain gnome-session-binary[1694]: WARNING: Child process 2032 was already dead.

Created attachment 1327602 [details]
system log when crash occured

(In reply to Mikhail from comment #5)
> I hope you got answer here:

Sure, there you go:

> [99333.663897] localhost.localdomain org.gnome.Shell.desktop[1821]: Key
> repeat discarded, Wayland compositor doesn't seem to be processing events
> fast enough!

That's a first sign of the system not being able to cope with events.

> [99334.060056] localhost.localdomain org.gnome.Shell.desktop[1821]: (EE)
> [99334.060056] localhost.localdomain org.gnome.Shell.desktop[1821]: Fatal
> server error:
> [99334.060056] localhost.localdomain org.gnome.Shell.desktop[1821]: (EE)
> Error sending request: Resource temporarily unavailable
> [99334.060056] localhost.localdomain org.gnome.Shell.desktop[1821]: (EE)

Basically, what that tells us is that the compositor (gnome-shell) is not fast enough to deal with events from Xwayland and the event queue fills up up until the point where the socket is full and libwayland bails out:

  https://cgit.freedesktop.org/wayland/wayland/tree/src/wayland-client.c?h=1.14#n657

So this is not really an Xwayland issue, it's in between gnome-shell/mutter (which doesn't dequeue Wayland events fast enough) and possibly the hardware/driver which can't deal with the load.

So it impossible to fix?
Machine is fast enough Core i7 + 32GB RAM. And I run very simple 2D game as Pacman.
Very annoying that it lead to incorrect terminating all working applications, lose all unsaved data,  and loosing login into session.

(In reply to Mikhail from comment #8)
> So it impossible to fix?

Cannot anser this without a clear understanding of what is causing this. We have the effect (Xwayland bails out because mutter/gnome-shell cannot cope with the number of Wayland requests sent by Xwayland), but we do not know why yet.

> Machine is fast enough Core i7 + 32GB RAM. And I run very simple 2D game as
> Pacman.

Which video hardware/driver is is using?

> Very annoying that it lead to incorrect terminating all working
> applications, lose all unsaved data,  and loosing login into session.

Yes, but that's another issue, mutter being unable to survive Xwayland, which is being addressed/discussed in other bugs.

> Which video hardware/driver is is using?
Intel® HD Graphics 4600

Created attachment 1328106 [details]
system log from another machine (Core(TM) i5-2310 +  Intel® HD Graphics 2000)

On another machine installed much older Fedora 26. But gnome-shell crashes too when I played PAC-MAN 256 few seconds. And I don't see messages "Wayland compositor doesn't seem to be processing events fast enough!" in system log.

Can you please try with weston to see if the issue occurs with a different Wayland compositor?

Which is yet another Wayland compositor exists in Fedora? I know only about kwin in KDE? I am not sure that kwin already can works in Wayland session.

Weston is the reference implementation of a Wayland compositor.

On Fedora, you can install it with "dnf install weston", that will add a new session "Weston" in the list of available sessions in gdm (*)

You may have to tweak your ~/.config/weston.ini to enable xwayland support in weston (see "man weson.ini" for more details), an example of a minimalist westom.ini I use can be found below:

#---------------------------------------------------------------------#
[core]
modules=xwayland.so
shell=desktop-shell.so

[shell]
background-color=0xff002244
panel-color=0x90ff0000
binding-modifier=alt

[launcher]
icon=/usr/share/icons/gnome/24x24/apps/utilities-terminal.png
path=/usr/bin/weston-terminal
#---------------------------------------------------------------------#


(*) Note: You can also try weston by switching to another VT and running "weston-launch" from the VT console as well, without leaving your session in GNOME.

To quit/terminale weston, simply press ctrl-alt-backspace.

Very interesting, but under weston this issue not happens.

PACMAN 256 on weston: https://youtu.be/sP_tNXn1H6A
PACMAN 256 on mutter (gnome-shell): https://youtu.be/VKinRNOUMA8

But I noted what the mouse pointer are shifted when I use weston . This can be seen on my video (mouse hover effect is shifted above and to the left with respect to the drawn mouse pointer)

(In reply to Mikhail from comment #16)
> Very interesting, but under weston this issue not happens.

So that confirms the problem is with gnome-shell/mutter and not Xwayland.

> But I noted what the mouse pointer are shifted when I use weston . This can
> be seen on my video (mouse hover effect is shifted above and to the left
> with respect to the drawn mouse pointer)

Unrelated.

This bug appears to have been reported against 'rawhide' during the Fedora 28 development cycle.
Changing version to '28'.

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