Created attachment 1738674 [details]
gdm debug log

Description of problem:
After user log in gdm start using 100% cpu from 1 core.

Version-Release number of selected component (if applicable):
3.38.1
3.38.2

How reproducible:
I am not sure. But it is confirmed on 2 different hardware. It is not clear to me if it bug, configuration or hardware.

Steps to Reproduce:
1. Install Fedora 33 on aarch64
2. Log in user
3. Check cpu use

Actual results:
gdm use 1 core 100% or more

Expected results:
gdm should be low on cpu after log in is finished

Additional info:
* I have tried both X11 and Wayland - same result.
* Tried to disable gdm and start gnome session with startx or "XDG_SESSION_TYPE=wayland dbus-run-session gnome-session" - system behave normal.

strace show gdm do a lot of ppoll - I have not been able to find out for what.

# strace -p 1025
strace: Process 1025 attached
ppoll([{fd=7, events=POLLIN}, {fd=10, events=POLLPRI}, {fd=11, events=POLLIN}, {fd=12, events=POLLIN}, {fd=18, events=POLLIN}, {fd=19, events=POLLIN}], 6, {tv_sec=0, tv_nsec=0}, NULL, 0) = 0 (Timeout)

# strace -c -fp 1025
strace: Process 1025 attached with 3 threads
^Cstrace: Process 1025 detached
strace: Process 1029 detached
strace: Process 1034 detached
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
100.00   15.112729           9   1525886           ppoll
------ ----------- ----------- --------- --------- ----------------
100.00   15.112729           9   1525886           total

# gdb --pid=1021
GNU gdb (GDB) Fedora 10.1-2.fc33

Attaching to process 1021
[New LWP 1029]
[New LWP 1034]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
0x0000ffff9b3fb5c0 in __GI___poll (fds=0xaaaad618d2c0, nfds=6, timeout=<optimized out>) at ../sysdeps/unix/sysv/linux/poll.c:41
41	  return SYSCALL_CANCEL (ppoll, fds, nfds, timeout_ts_p, NULL, 0);

(gdb) bt
#0  0x0000ffff9b3fb5c0 in __GI___poll (fds=0xaaaad618d2c0, nfds=6, timeout=<optimized out>) at ../sysdeps/unix/sysv/linux/poll.c:41
#1  0x0000ffff9b8747d0 in g_main_context_poll (priority=<optimized out>, n_fds=6, fds=0xaaaad618d2c0, timeout=<optimized out>, 
    context=0xaaaad6132b10) at ../glib/gmain.c:4422
#2  g_main_context_iterate.constprop.0 (context=0xaaaad6132b10, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>)
    at ../glib/gmain.c:4114
#3  0x0000ffff9b81df80 in g_main_loop_run (loop=0xaaaad6141710) at ../glib/gmain.c:4317
#4  0x0000aaaac4581ec8 in main (argc=<optimized out>, argv=<optimized out>) at ../daemon/main.c:395

(gdb) t apply all bt

Thread 3 (Thread 0xffff87ffeff0 (LWP 1034) "gdbus"):
#0  0x0000ffff9b3fb5c0 in __GI___poll (fds=0xffff8000ccd0, nfds=3, timeout=<optimized out>) at ../sysdeps/unix/sysv/linux/poll.c:41
#1  0x0000ffff9b8747d0 in g_main_context_poll (priority=<optimized out>, n_fds=3, fds=0xffff8000ccd0, timeout=<optimized out>, context=0xaaaad613b060) at ../glib/gmain.c:4422
#2  g_main_context_iterate.constprop.0 (context=0xaaaad613b060, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at ../glib/gmain.c:4114
#3  0x0000ffff9b81df80 in g_main_loop_run (loop=0xaaaad613b150) at ../glib/gmain.c:4317
#4  0x0000ffff9b6ec298 in gdbus_shared_thread_func (user_data=0xaaaad613b030) at ../gio/gdbusprivate.c:280
#5  0x0000ffff9b84e498 in g_thread_proxy (data=0xaaaad612a180) at ../glib/gthread.c:820
#6  0x0000ffff9b0e40c8 in start_thread (arg=0x0) at pthread_create.c:463
#7  0x0000ffff9b405d1c in thread_start () at ../sysdeps/unix/sysv/linux/aarch64/clone.S:78

Thread 2 (Thread 0xffff8c8b5ff0 (LWP 1029) "gmain"):
#0  0x0000ffff9b3fb5c0 in __GI___poll (fds=0xaaaad6127560, nfds=1, timeout=<optimized out>) at ../sysdeps/unix/sysv/linux/poll.c:41
#1  0x0000ffff9b8747d0 in g_main_context_poll (priority=<optimized out>, n_fds=1, fds=0xaaaad6127560, timeout=<optimized out>, context=0xaaaad6129390) at ../glib/gmain.c:4422
#2  g_main_context_iterate.constprop.0 (context=context@entry=0xaaaad6129390, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at ../glib/gmain.c:4114
#3  0x0000ffff9b81b80c in g_main_context_iteration (context=0xaaaad6129390, may_block=may_block@entry=1) at ../glib/gmain.c:4184
#4  0x0000ffff9b81d704 in glib_worker_main (data=<optimized out>) at ../glib/gmain.c:6077
#5  0x0000ffff9b84e498 in g_thread_proxy (data=0xaaaad610fea0) at ../glib/gthread.c:820
#6  0x0000ffff9b0e40c8 in start_thread (arg=0x0) at pthread_create.c:463
#7  0x0000ffff9b405d1c in thread_start () at ../sysdeps/unix/sysv/linux/aarch64/clone.S:78

Thread 1 (Thread 0xffff9ad7b010 (LWP 1021) "gdm"):
#0  0x0000ffff9b3fb5c0 in __GI___poll (fds=0xaaaad618d2c0, nfds=6, timeout=<optimized out>) at ../sysdeps/unix/sysv/linux/poll.c:41
#1  0x0000ffff9b8747d0 in g_main_context_poll (priority=<optimized out>, n_fds=6, fds=0xaaaad618d2c0, timeout=<optimized out>, context=0xaaaad6132b10) at ../glib/gmain.c:4422
#2  g_main_context_iterate.constprop.0 (context=0xaaaad6132b10, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at ../glib/gmain.c:4114
#3  0x0000ffff9b81df80 in g_main_loop_run (loop=0xaaaad6141710) at ../glib/gmain.c:4317
#4  0x0000aaaac4581ec8 in main (argc=<optimized out>, argv=<optimized out>) at ../daemon/main.c:395

* I turned on gdm debug - attach the log.