Recent kernel upgrade & Radeon RX 5700 XT - Xorg crashes when evolution is invoked

[ja]

Hi
I have recently put together a new machine using
an RX 5700 XT graphics card & X570 motherboard.
I have been using it for about a month.
My understanding is that kernel 5.3 provides "fuller" support for RX 5700
graphics

With the 5.2 kernel (eg 5.2.18-200.fc30.x86_64) it has been working fine.
Only one resolution appeared available but it seemed to work OK
xrandr shows
	Screen 0: minimum 1920 x 1080, current 1920 x 1080, maximum 1920 x 1080
	default connected 1920x1080+0+0 0mm x 0mm
   1920x1080     77.00*

Today's update to 5.3 (5.3.5-200.fc30.x86_64) causes Xorg to crash
when evolution is used.
Xorg restarts and returns the user to the login screen.

Other applications seem to work OK google-chrome, google-earth, brave-browser,
pcmanfm, 

xrandr now shows loads of different resolutions (but not that given above)
	Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 16384 x 16384
	DP-1 disconnected (normal left inverted right x axis y axis)
	DP-2 disconnected (normal left inverted right x axis y axis)
	DP-3 disconnected (normal left inverted right x axis y axis)
	HDMI-1 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 477mm x 268mm
	1920x1080     60.00*+  59.96    60.00    50.00    59.94    59.93
	...

Further tests show that
Logging in as "fred" and "su - ted"  & running evolution as ted
avoids the crash.
Logging in as "fred" and "su - fred" & running evolution as fred
crashes Xorg

Any thoughts/advice?

John

//-------------------------------------------------------------------------------------------------
/var/log/Xorg.0.log.old shows

[   530.028] (II) modeset(0): Modeline "1152x864"x0.0  108.00  1152 1216 1344
1600  864 865 868 900 +hsync +vsync (67.5 kHz e)
[   530.028] (II) modeset(0): Modeline "1440x900"x0.0  136.75  1440 1536 1688
1936  900 903 909 942 -hsync +vsync (70.6 kHz e)
[  1793.339] (EE) 
[  1793.339] (EE) Backtrace:
[  1793.340] (EE) 0: /usr/libexec/Xorg (OsLookupColor+0x13c) [0x564a610dbd2c]
[  1793.340] (EE) 1: /lib64/libpthread.so.0 (funlockfile+0x50) [0x7fe5322c6caf]
[  1793.340] (EE) 2: /lib64/libc.so.6 (gsignal+0x145) [0x7fe532125e35]
[  1793.341] (EE) 3: /lib64/libc.so.6 (abort+0x127) [0x7fe532110895]
[  1793.341] (EE) 4: /lib64/libc.so.6 (__assert_fail_base.cold+0xf) [0x7fe532110769]
[  1793.341] (EE) 5: /lib64/libc.so.6 (__assert_fail+0x46) [0x7fe53211e566]
[  1793.341] (EE) 6: /usr/libexec/Xorg (DRIMoveBuffersHelper+0xc15) [0x564a610a6e15]
[  1793.341] (EE) 7: /usr/libexec/Xorg (DRI2Authenticate+0xa2) [0x564a610a8462]
[  1793.341] (EE) 8: /usr/libexec/Xorg (DRI2GetParam+0x944) [0x564a610a9814]
[  1793.341] (EE) 9: /usr/libexec/Xorg (SendErrorToClient+0x354) [0x564a60f7cd94]
[  1793.341] (EE) 10: /usr/libexec/Xorg (InitFonts+0x3b4) [0x564a60f80e34]
[  1793.342] (EE) 11: /lib64/libc.so.6 (__libc_start_main+0xf3) [0x7fe532111f43]
[  1793.342] (EE) 12: /usr/libexec/Xorg (_start+0x2e) [0x564a60f6a86e]
[  1793.342] (EE) 
[  1793.342] (EE) 
Fatal server error:
[  1793.342] (EE) Caught signal 6 (Aborted). Server aborting
[  1793.342] (EE) 
[  1793.342] (EE) 
Please consult the Fedora Project support 
	 at http://wiki.x.org
 for help. 
[  1793.342] (EE) Please also check the log file at "/var/log/Xorg.0.log" for
additional information.
[  1793.342] (EE) 
[  1793.383] (EE) Server terminated with error (1). Closing log file.
//-------------------------------------------------------------------------------------------------
journalctl shows

                                                           Stack trace of thread 4693:
                                                           #0  0x00007fe532125e35 raise
(libc.so.6)
                                                           #1  0x00007fe532110895 abort
(libc.so.6)
                                                           #2  0x0000564a610de940 OsAbort
(Xorg)
                                                           #3  0x0000564a610e4539
AbortServer (Xorg)
                                                           #4  0x0000564a610e539a
FatalError (Xorg)
                                                           #5  0x0000564a610dbc89
OsSigHandler (Xorg)
                                                           #6  0x00007fe5322c6c60
__restore_rt (libpthread.so.0)
                                                           #7  0x00007fe532125e35 raise
(libc.so.6)
                                                           #8  0x00007fe532110895 abort
(libc.so.6)
                                                           #9  0x00007fe532110769
__assert_fail_base.cold (libc.so.6)
                                                           #10 0x00007fe53211e566
__assert_fail (libc.so.6)
                                                           #11 0x0000564a610a6225
dixGetPrivateAddr.isra.0.part.0 (Xorg)
                                                           #12 0x0000564a610a8462
DRI2Authenticate (Xorg)
                                                           #13 0x0000564a610a9484
ProcDRI2Dispatch (Xorg)
                                                           #14 0x0000564a60f7cd34 Dispatch
(Xorg)
                                                           #15 0x0000564a60f80df4 dix_main
(Xorg)
                                                           #16 0x00007fe532111f43
__libc_start_main (libc.so.6)
                                                           #17 0x0000564a60f6a86e _start
(Xorg)
                                                           
                                                           Stack trace of thread 4722:
                                                           #0  0x00007fe5322c23c5
pthread_cond_wait@(a)GLIBC_2.3.2 (libpthread.so.0)
                                                           #1  0x00007fe52b109c13 cnd_wait
(swrast_dri.so)
                                                           #2  0x00007fe52b109a7b
impl_thrd_routine (swrast_dri.so)
                                                           #3  0x00007fe5322bc4c0
start_thread (libpthread.so.0)
                                                           #4  0x00007fe5321ea553 __clone
(libc.so.6)

                                                           ...

                                                           #0  0x00007fe5322c23c5
pthread_cond_wait@(a)GLIBC_2.3.2 (libpthread.so.0)
                                                           #1  0x00007fe52b109c13 cnd_wait
(swrast_dri.so)
                                                           #2  0x00007fe52b109a7b
impl_thrd_routine (swrast_dri.so)
                                                           #3  0x00007fe5322bc4c0
start_thread (libpthread.so.0)
                                                           #4  0x00007fe5321ea553 __clone
(libc.so.6)