Hello Prarit,
it looks like your commit f9a75c1d717f ("modules: Only return -EEXIST
for modules that have finished loading") _sometimes_ causes hangs on
s390. This is unfortunately not 100% reproducible, however the
mentioned commit seems to be the only relevant one in modules.c.
What I see is a hanging system with messages like this on the console:
[ 65.876040] rcu: INFO: rcu_sched self-detected stall on CPU
[ 65.876049] rcu: 7-....: (5999 ticks this GP) idle=eae/1/0x4000000000000002 softirq=1181/1181 fqs=2729
[ 65.876078] (t=6000 jiffies g=-471 q=17196)
[ 65.876084] Task dump for CPU 7:
[ 65.876088] systemd-udevd R running task 0 731 721 0x06000004
[ 65.876097] Call Trace:
[ 65.876113] ([<0000000000abb264>] __schedule+0x2e4/0x6e0)
[ 65.876122] [<00000000001ee486>] finished_loading+0x4e/0xb0
[ 65.876128] [<00000000001f1ed6>] load_module+0xcce/0x27a0
[ 65.876134] [<00000000001f3af0>] __s390x_sys_init_module+0x148/0x178
[ 65.876142] [<0000000000ac0766>] system_call+0x2aa/0x2c8
crash's backtrace of this task looks like this:
PID: 731 TASK: 1e79ba000 CPU: 7 COMMAND: "systemd-udevd"
LOWCORE INFO:
-psw : 0x0704c00180000000 0x0000000000ab666a
-function : memcmp at ab666a
-prefix : 0x7fe32000
-cpu timer: 0x7fffff5784d0f048
-clock cmp: 0xd60757081cd70d00
-general registers:
0x0000000000000009 0x0000000000000009
0x000003ff80347321 000000000000000000
0x000003ff8034f321 000000000000000000
0x000000000000001e 0x000003ff8c592708
0x000003e0047da900 0x000003ff8034f318
0x0000000000000001 0x0000000000000009
0x000003ff80347300 0x0000000000ad81b8
0x00000000001ee062 0x000003e004357cb0
[...]
#0 [3e004357cf0] load_module at 1f1eb0
#1 [3e004357dd0] __se_sys_init_module at 1f3af0
#2 [3e004357ea8] system_call at ac0766
PSW: 0705000180000000 000003ff8c27ad3e (user space)
GPRS: 000002aa280d2fb0 000003ff8c27ad3c 0000000000000080 00000000000035fd
000003ff8c592708 000002aa280c8770 0000000000000000 000002aa280d7130
0000000000020000 000002aa28915760 000003ff8c592708 000002aa280c00b0
000003ff8c8fff80 000002aa280c00b0 000003ff8c58a456 000003ffe9cfde90
I did not look any further into the dump, however since the commit
touches exactly the code path which seems to be looping... ;)
