Hi all,
In my s390x archtecture, kprobe_eventname selftest have always failed because of rcu_sched stalls.
My environment is QEMU Ubuntu 24.04 KVM Machine Linux version 6.8.0-36-generic (buildd@bos01-s390x-012) (s390x-linux-gnu-gcc-13 (Ubuntu 13.2.0-23ubuntu4) 13.2.0, GNU ld (GNU Binutils for Ubuntu) 2.42) #36
1 configured CPUs, Linux is running under KVM in 64-bit mode
qemu-system-s390x -no-reboot -name auto-inst-test -nographic -m 4096 \ -drive file=disk-image.qcow2,format=qcow2,cache=none,if=virtio \ -netdev user,id=enc0,hostfwd=tcp::10000-:22 \ -device virtio-net-ccw,netdev=enc0 \ -qmp tcp:localhost:4444,server,nowait
Currently, This failure can be always reproduced by this kselftests script:
# tools/testing/selftests/ftrace/ftracetest tools/testing/selftests/ftrace/test.d/kprobe/kprobe_eventname.tc
I've investigating cause of line, then I find this line.
for i in `seq 0 255`; do echo p $FUNCTION_FORK+${i} >> kprobe_events || continue done
cat kprobe_events >> $testlog
echo 1 > events/kprobes/enable # <<<
This line makes "rcu_sched detected stalls" log and stall the system.
[ 7825.578940] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
After this line, the test doesn't go any further.
This test was added in the patch below.
("selftests/ftrace: Add new test case which adds multiple consecutive probes in a function") Link: https://lore.kernel.org/linux-trace-kernel/20230428163842.95118-2-akanksha@l...
I've attached a link to a compressed version of vmcore, vmlinux and config files that I dumped from my environment.
https://drive.google.com/file/d/1O2bCKrRbyJ-yP4zTz_sAd_qM80nHnCGr/view?usp=s...
I used QEMU QMP to dump the vmcore.
$ telnet localhost 4444
{"execute": "qmp_capabilities"}
{"execute":"dump-guest-memory","arguments": {"paging":false,"protocol":"file:/home/paran/vmcore1.img"}}
rcu: INFO: rcu_sched detected stalls on CPUs/tasks:s: rcu: (detected by 0, t=6002 jiffies, g=24353, q=1 ncpus=1)1) rcu: All QSes seen, last rcu_sched kthread activity 6002 (4294978930-4294972928), jiffies_till_next_fqs=1, root ->qsmask 0x0x0 rcu: rcu_sched kthread starved for 6002 jiffies! g24353 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0=0 rcu: Unless rcu_sched kthread gets sufficient CPU time, OOM is now expected behavior.r. rcu: RCU grace-period kthread stack dump:p: task:rcu_sched state:R running task stack:0 pid:16 tgid:16 ppid:2 flags:0x0000000000 Call Trace:e: __schedule+0x346/0x8b8 8 schedule+0x36/0x148 8 schedule_timeout+0x8e/0x148 8 rcu_gp_fqs_loop+0x444/0x548 8 rcu_gp_kthread+0x146/0x198 8 kthread+0x124/0x128 8 __ret_from_fork+0x40/0x58 8 ret_from_fork+0xa/0x30 0 rcu: Stack dump where RCU GP kthread last ran:n: CPU: 0 PID: 1077 Comm: ftracetest Not tainted 6.8.0-36-generic #36-Ubuntu Hardware name: QEMU 8561 QEMU (KVM/Linux) Krnl PSW : 0704f00180000000 0000000000121d32 kprobe_exceptions_notify (/build/linux-3nCxw2/linux-6.8.0/arch/s390/kernel/kprobes.c:519 (discriminator 1)) R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:3 PM:0 RI:0 EA:3:3 Krnl GPRS: 0000000000000000 0000000000000000 0000000000008001 0000000000000000 0000000000000000 0000000000000000 0000000000000000 0000000001956720 ffffffffffffffff 0000000000121c98 0000000001958d40 00000380000cfbd8 000003ff938dbc78 00000380000cfab8 0000000000121d1c 00000380000cf980 Krnl Code: 0000000000121d26: 9103b008
Code starting with the faulting instruction =========================================== 8(%r11),3 0000000000121d2a: a7840004 8,0000000000121d32 #0000000000121d2e: ad03f0a0 stosm 160(%r15),3
0000000000121d32: b9140022
lgfr %r2,%r2 0000000000121d36: ebbff0a80004 %r11,%r15,168(%r15) 0000000000121d3c: a7190000 lghi %r1,0 0000000000121d40: a7390000 lghi %r3,0 0000000000121d44: a7490000 lghi %r4,0 Call Trace: kprobe_exceptions_notify (/build/linux-3nCxw2/linux-6.8.0/arch/s390/kernel/kprobes.c:519 (discriminator 1)) kprobe_exceptions_notify (/build/linux-3nCxw2/linux-6.8.0/arch/s390/kernel/kprobes.c:504 (discriminator 1)) notifier_call_chain (/build/linux-3nCxw2/linux-6.8.0/kernel/notifier.c:93) notify_die (/build/linux-3nCxw2/linux-6.8.0/kernel/notifier.c:597) do_per_trap (/build/linux-3nCxw2/linux-6.8.0/arch/s390/kernel/traps.c:75 (discriminator 1)) __do_pgm_check (/build/linux-3nCxw2/linux-6.8.0/arch/s390/include/asm/irqflags.h:47 (discriminator 1) /build/linux-3nCxw2/linux-6.8.0/arch/s390/include/asm/irqflags.h:52 (discriminator 1) /build/linux-3nCxw2/linux-6.8.0/arch/s390/kernel/traps.c:356 (discriminator 1)) pgm_check_handler (/build/linux-3nCxw2/linux-6.8.0/arch/s390/kernel/entry.S:383) kernel_clone (/build/linux-3nCxw2/linux-6.8.0/arch/s390/include/asm/uaccess.h:119 (discriminator 1) /build/linux-3nCxw2/linux-6.8.0/kernel/fork.c:2927 (discriminator 1)) __do_sys_clone (/build/linux-3nCxw2/linux-6.8.0/kernel/fork.c:3055) __s390x_sys_clone (/build/linux-3nCxw2/linux-6.8.0/kernel/fork.c:3027) __do_syscall (/build/linux-3nCxw2/linux-6.8.0/arch/s390/include/asm/ptrace.h:195 (discriminator 3) /build/linux-3nCxw2/linux-6.8.0/arch/s390/include/asm/ptrace.h:200 (discriminator 3) /build/linux-3nCxw2/linux-6.8.0/arch/s390/kernel/syscall.c:145 (discriminator 3) /build/linux-3nCxw2/linux-6.8.0/arch/s390/kernel/syscall.c:168 (discriminator 3)) system_call (/build/linux-3nCxw2/linux-6.8.0/arch/s390/kernel/entry.S:309) Last Breaking-Event-Address: 0xfdf5045050 ?rcu: INFO: rcu_sched detected stalls on CPUs/tasks:s: @rcu: (detected by 0, t=24007 jiffies, g=24353, q=1 ncpus=1) rcu: All QSes seen, last rcu_sched kthread activity 24007 (4294996935-4294972928), jiffies_till_next_fqs=1, root ->qsmask 0x0x0 rcu: rcu_sched kthread starved for 24007 jiffies! g24353 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0=0 rcu: Unless rcu_sched kthread gets sufficient CPU time, OOM is now expected behavior.r. rcu: RCU grace-period kthread stack dump:p: task:rcu_sched state:R running task stack:0 pid:16 tgid:16 ppid:2 flags:0x0000000000 Call Trace:e: __schedule+0x346/0x8b8 8 schedule+0x36/0x148 8 schedule_timeout+0x8e/0x148 8 rcu_gp_fqs_loop+0x444/0x548 8 rcu_gp_kthread+0x146/0x198 8 kthread+0x124/0x128 8 __ret_from_fork+0x40/0x58 8 ret_from_fork+0xa/0x30 0 rcu: Stack dump where RCU GP kthread last ran:n: CPU: 0 PID: 1077 Comm: ftracetest Not tainted 6.8.0-36-generic #36-Ubuntu Hardware name: QEMU 8561 QEMU (KVM/Linux) Krnl PSW : 0704d00180000000 0000000000ebe0b2 __do_pgm_check (/build/linux-3nCxw2/linux-6.8.0/arch/s390/kernel/traps.c:353) R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:1 PM:0 RI:0 EA:3:3 Krnl GPRS: 0704c00180000000 0000000000000000 00000380000cfb97 0000000000000000 0000000000000000 0704c00180000000 0000000000000000 0000000000000000 0704c00180000000 00000000001a8388 0000000000000000 00000380000cfbd8 000003ff938dbc78 0000000000ed1c6c 0000000000ebe024 00000380000cfaf0 Krnl Code: 0000000000ebe0a4: a504bfff
Code starting with the faulting instruction =========================================== nihh %r0,49151 0000000000ebe0a8: e300f0a80024 %r0,168(%r15) #0000000000ebe0ae: 8000f0a8 168(%r15)
0000000000ebe0b2: 5850b0a0
%r5,160(%r11) 0000000000ebe0b6: c05b0000007f nilf %r5,127 0000000000ebe0bc: a7840012 8,0000000000ebe0e0 0000000000ebe0c0: b91600e5 llgfr %r14,%r5 0000000000ebe0c4: c0400051121e larl %r4,00000000018e0500 Call Trace: __do_pgm_check (/build/linux-3nCxw2/linux-6.8.0/arch/s390/kernel/traps.c:353) __do_pgm_check (/build/linux-3nCxw2/linux-6.8.0/arch/s390/kernel/traps.c:318) pgm_check_handler (/build/linux-3nCxw2/linux-6.8.0/arch/s390/kernel/entry.S:383) kernel_clone (/build/linux-3nCxw2/linux-6.8.0/arch/s390/include/asm/uaccess.h:119 (discriminator 1) /build/linux-3nCxw2/linux-6.8.0/kernel/fork.c:2927 (discriminator 1)) __do_sys_clone (/build/linux-3nCxw2/linux-6.8.0/kernel/fork.c:3055) __s390x_sys_clone (/build/linux-3nCxw2/linux-6.8.0/kernel/fork.c:3027) __do_syscall (/build/linux-3nCxw2/linux-6.8.0/arch/s390/include/asm/ptrace.h:195 (discriminator 3) /build/linux-3nCxw2/linux-6.8.0/arch/s390/include/asm/ptrace.h:200 (discriminator 3) /build/linux-3nCxw2/linux-6.8.0/arch/s390/kernel/syscall.c:145 (discriminator 3) /build/linux-3nCxw2/linux-6.8.0/arch/s390/kernel/syscall.c:168 (discriminator 3)) system_call (/build/linux-3nCxw2/linux-6.8.0/arch/s390/kernel/entry.S:309) Last Breaking-Event-Address: 0x4404c0018000000000
It's not easy for me to resolve this issue. If advice or guidance can be provided on how to resolve this issue, I'll try sending a patch!
Warm regards, Yunseong Kim