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Created attachment 1226610 [details] output of "dmesg" command Description of problem: Fedora 25 (64-bit), freshly installed from Live/Workstation image, including all updates. No changes to Xorg configuration. On GNOME desktop (with Xorg, not Wayland), when switching from (default) anti-aliased font display to non-antialiased fonts, Xorg crashes on next login. Makes it basically impossible for the user to ever login again. Xorg is a SUID root binary. Don't know if that crash may affect security. The crash does not happen with Wayland (instead of Xorg). The crash seems to be dependent on graphics hardware/driver, in this case Nvidia (nouveau). No crash with same setup on notebook with Intel i915 graphics. Setting the nouveau kernel option NoAccel=1 will avoid the crash (but makes the PC useless for video playback). Not all anti-aliased fonts seem to crash Xorg, but especially the Italics variants are a major problem (this can be verified by not disabling anti-aliasing completely but using fontconfig to disable it only for specific fonts). I have no idea what makes rendering of Italics variants so difficult for the graphics drivers. Using Fedora for years (including F24), same hardware, never experienced any problems like this. Version-Release number of selected component (if applicable): xorg-x11-server-Xorg-1.19.0-1.fc25.x86_64 xorg-x11-drv-nouveau-1.0.13-1.fc25.x86_64 How reproducible: Always. Steps to Reproduce: 1. Create a fresh user account and login on "gdm" graphics screen, but select "GNOME on Xorg" (not default Wayland). 2. Ignore the Welcome window (gnome-initial-setup), don't close it, let it stay open. 2. Open a "Terminal" (gnome-terminal) and enter "gsettings set org.gnome.settings-daemon.plugins.xsettings antialiasing none". Or use "gnome-tweak-tool", same result. 3. Logout. 4. Login again with same user. 5. As soon as the Welcome window (gnome-initial-setup) opens, Xorg crashes (always, so there's no login possible any longer). 6. In this example, "gnome-initial-setup" just helps to trigger the bug. Other GNOME apps like "gnome-terminal" would trigger the bug as well. Actual results: Xorg crashes when font anti-aliasing is turned off. Expected results: Xorg does not crash, no matter how fonts are configured. Additional info: This may be related to bug #1398071 (but triggered by startx/fontconfig).
Created attachment 1226613 [details] Xorg log from ~/.local/share/xorg/ This is from the second login when the crash occurs.
Created attachment 1226614 [details] Xorg log from ~/.local/share/xorg/ This is from the first login before the crash occurs.
Are you sure it's Xorg and not GNOME shell or gnome-session? I see no indication of crash nor backtrace of Xorg in neither dmesg (attachment 1226610 [details]) nor the logs (attachment 1226613 [details], attachment 1226614 [details]) [ 252.769] (II) Server terminated successfully (0). Closing log file. Out of curiosity, does the same occurs when using the modesettings driver instead of the nouveau driver?
How can I find out which component actually crashes? From a user perspective, the session abruptly ends and the user is put back to the login screen. No notification or log what happened. This bug seems to be related to bug #1398071 (I didn't know for sure when I created this one - just realised afterwards that both are related to font anti-aliasing). Bug #1398071 works with startx/Xorg directly without gnome-shell or gnome-session. Regarding your last question, I'm not sure of this is the proper way to use "modesetting" instead of "nouveau" (default): /etc/X11/xorg.conf.d/99-modesetting.conf Section "Monitor" Identifier "Monitor0" EndSection Section "Device" Identifier "Device0" Driver "modesetting" Option "AccelMethod" "none" EndSection Section "Screen" Identifier "Screen0" Monitor "Monitor0" Device "Device0" EndSection I don't know how to verify that Xorg actually uses "modesetting", but at least the font anti-aliasing crash was gone. However, with default "AccelMethod" (glamor), other programs (eg, mplayer) crash the X server really badly. So I had to disable acceleration (AccelMethod=none) which also disables essential video playback functionality (similar to NoAccel=1 for nouveau, which also makes the crashes go away). Not a real workaround rather than a hint where to search for the bug. Chances are, the Xorg crash may be caused by some acceleration code in the nouveau driver that changed between F24 (xorg-x11-drv-nouveau-1.0.12-4.fc24.x86_64) and F25 (xorg-x11-drv-nouveau-1.0.13-1.fc25.x86_64).
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