Re: the stuttering regression in 7.0: should I have done something different?

[Tony Rodriguez]

Just confirmed on my end today.  This regression also impacts both 
SPARC64 S7-2 and SPARC64 T7-1 on v7.0.4 and v7.1-rc2 as well. Different 
systems using the same exact kernels.

** Please see points (A1) (A2) (B1) (B2)

Once again, I am not experiencing such issues when "my patch" (link 
below) is added to address this regression.

https://github.com/sparclinux/issues/issues/79#issuecomment-4362173884

Output demonstrating issues for SPARC64 S7-2 and T7-1 systems (without 
my regression patch):

PS - On May 2nd 2026 at 9:42 PM: I also sent an email to Thomas Gleixner 
regarding this issue.  Will be happy to validate any patches from your 
end regarding this issue, as time permits me to do so.


Best Regards,

Tony Rodriguez


 A1) SPARC64 S7-2: Kernel v7.1.0-rc2
uname -a
Linux s7t7-debian-test 7.1.0-rc2-test01 #1 SMP Fri May  8 10:02:12 PDT 
2026 sparc64 GNU/Linux

cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-7.1.0-rc2-test01 
root=UUID=ce937a4b-126a-41bd-a54b-03a424421086 ro console=ttyHV0,9600n81 
systemd.log_level=info systemd.show_status=1 
systemd.journald.forward_to_console=0 plymouth.enable=0 quiet

[  243.267359] INFO: task kworker/u512:1:706 blocked for more than 120 
seconds.
[  243.281208]       Not tainted 7.1.0-rc2-test01 #1
[  243.290583] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" 
disables this message.
[  243.306349] INFO: task kworker/127:1:714 blocked for more than 120 
seconds.
[  243.320106]       Not tainted 7.1.0-rc2-test01 #1
[  243.329476] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" 
disables this message.

[  364.099350] INFO: task kworker/u512:1:706 blocked for more than 241 
seconds.
[  364.113199]       Not tainted 7.1.0-rc2-test01 #1
[  364.122585] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" 
disables this message.
[  364.138328] INFO: task kworker/127:1:714 blocked for more than 241 
seconds.
[  364.152086]       Not tainted 7.1.0-rc2-test01 #1
[  364.161470] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" 
disables this message.

[  485.295360] INFO: task kworker/u512:1:706 blocked for more than 362 
seconds.
[  485.309209]       Not tainted 7.1.0-rc2-test01 #1
[  485.318581] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" 
disables this message.
[  485.334345] INFO: task kworker/127:1:714 blocked for more than 362 
seconds.
[  485.348099]       Not tainted 7.1.0-rc2-test01 #1
[  485.357467] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" 
disables this message.

[  726.849598] INFO: task kworker/u512:1:706 blocked for more than 604 
seconds.
[  726.863444]       Not tainted 7.1.0-rc2-test01 #1
[  726.872832] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" 
disables this message.
[  726.888573] INFO: task kworker/127:1:714 blocked for more than 604 
seconds.
[  726.902340]       Not tainted 7.1.0-rc2-test01 #1
[  726.911708] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" 
disables this message.

sudo dmesg | grep -iE block | grep -iE worker
[  243.267359] INFO: task kworker/u512:1:706 blocked for more than 120 
seconds.
[  243.306349] INFO: task kworker/127:1:714 blocked for more than 120 
seconds.
[  364.099350] INFO: task kworker/u512:1:706 blocked for more than 241 
seconds.
[  364.138328] INFO: task kworker/127:1:714 blocked for more than 241 
seconds.
[  485.295360] INFO: task kworker/u512:1:706 blocked for more than 362 
seconds.
[  485.334345] INFO: task kworker/127:1:714 blocked for more than 362 
seconds.
[  605.849474] INFO: task kworker/u512:1:706 blocked for more than 483 
seconds.
[  605.888461] INFO: task kworker/127:1:714 blocked for more than 483 
seconds.

sudo poweroff or sudo reboot
NOTE(S): Random hangs during startup. Also, hangs during shutdown/reboot 
process.
-------------------------------------------------------------------------------------------
A2) SPARC64 S7-2: Kernel v7.0.4
[  OK  ] Finished e2scrub_reap.service - Remove Stale Online ext4 
Metadata Check Snapshots.

Debian GNU/Linux forky/sid s7t7-debian-test ttyHV0

s7t7-debian-test login: tonyr
Password:
Linux s7t7-debian-test 7.0.4-test01 #1 SMP Fri May  8 09:27:58 PDT 2026 
sparc64
[...]
Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.

login: timed [  114.687722] rcu: INFO: rcu_sched detected stalls on 
CPUs/tasks:
[  114.699319] rcu:     67-...!: (240 GPs behind) idle=e9c0/0/0x0 
softirq=174/174 fqs=0 (false positive?)
[  114.717370] rcu:     102-...!: (73 GPs behind) idle=77e0/0/0x0 
softirq=286/287 fqs=0 (false positive?)
[  114.735419] rcu:     111-...!: (52 GPs behind) idle=11d8/0/0x0 
softirq=860/861 fqs=0 (false positive?)
[  114.753489] rcu:     (detected by 11, t=5268 jiffies, g=4457, q=528 
ncpus=128)
[  114.767628] rcu: rcu_sched kthread timer wakeup didn't happen for 
5270 jiffies! g4457 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
[  114.789647] rcu:     Possible timer handling issue on cpu=105 
timer-softirq=98
[  114.803535] rcu: rcu_sched kthread starved for 5280 jiffies! g4457 
f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=105
[  114.824201] rcu:     Unless rcu_sched kthread gets sufficient CPU 
time, OOM is now expected behavior.
[  114.842080] rcu: RCU grace-period kthread stack dump:
[  114.852221] rcu: Stack dump where RCU GP kthread last ran:
[  135.867723] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
[  135.879326] rcu:     65-...!: (1 GPs behind) idle=35b0/0/0x0 
softirq=483/484 fqs=0 (false positive?)
[  135.897024] rcu:     67-...!: (241 GPs behind) idle=ecc0/0/0x0 
softirq=174/174 fqs=0 (false positive?)
[  135.915082] rcu:     102-...!: (74 GPs behind) idle=7800/0/0x0 
softirq=286/287 fqs=0 (false positive?)
[  135.933123] rcu:     111-...!: (53 GPs behind) idle=1238/0/0x0 
softirq=860/861 fqs=0 (false positive?)
[  135.951184] rcu:     (detected by 64, t=5272 jiffies, g=4461, q=752 
ncpus=128)
[  135.965398] rcu: rcu_sched kthread timer wakeup didn't happen for 
5275 jiffies! g4461 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
[  135.987393] rcu:     Possible timer handling issue on cpu=105 
timer-softirq=98
[  136.001287] rcu: rcu_sched kthread starved for 5285 jiffies! g4461 
f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=105
[  136.021944] rcu:     Unless rcu_sched kthread gets sufficient CPU 
time, OOM is now expected behavior.
[  136.039829] rcu: RCU grace-period kthread stack dump:
[  136.049971] rcu: Stack dump where RCU GP kthread last ran:

NOTE(S): Unable to login and random hangs during system startup.
-------------------------------------------------------------------------
B1) SPARC64 T7-1: Kernel v7.1.0-rc2
lscpu;uname -a
Architecture:          sparc64
  CPU op-mode(s):      32-bit, 64-bit
  Byte Order:          Big Endian
CPU(s):                256
  On-line CPU(s) list: 0-255
Model name:            SPARC-M7
  Thread(s) per core:  8
  Core(s) per socket:  32
  Socket(s):           1
  Flags:               sun4v
Caches (sum of all):
  L1d:                 4 MiB (256 instances)
  L1i:                 4 MiB (256 instances)
  L2:                  64 MiB (256 instances)
Linux s7t7-debian-test 7.1.0-rc2-test01 #1 SMP Fri May  8 10:02:12 PDT 
2026 sparc64 GNU/Linux

  526.766867] rcu:     8-...!: (806 GPs behind) idle=069c/0/0x1 
softirq=682/682 fqs=0
[  526.781618] rcu:     22-...!: (0 ticks this GP) idle=7b40/0/0x0 
softirq=739/739 fqs=0 (false positive?)
[  526.799841] rcu:     89-...!: (770 GPs behind) idle=7800/0/0x0 
softirq=270/273 fqs=0 (false positive?)
[  526.817901] rcu:     112-...!: (225 GPs behind) idle=c0c8/0/0x0 
softirq=193/193 fqs=0 (false positive?)
[  526.836131] rcu:     189-...!: (0 ticks this GP) idle=8ef0/0/0x0 
softirq=1016/1016 fqs=0 (false positive?)
[  526.854885] rcu:     204-...!: (0 ticks this GP) idle=5d20/0/0x0 
softirq=774/774 fqs=0 (false positive?)
[  526.873278] rcu:     219-...!: (225 GPs behind) idle=d580/0/0x0 
softirq=605/607 fqs=0 (false positive?)
[  526.891508] rcu:     226-...!: (233 GPs behind) idle=ec08/0/0x0 
softirq=1189/1190 fqs=0 (false positive?)
[  526.910079] rcu:     (detected by 157, t=5289 jiffies, g=5989, q=5339 
ncpus=256)
[  526.924916] rcu: rcu_sched kthread timer wakeup didn't happen for 
5295 jiffies! g5989 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
[  526.946930] rcu:     Possible timer handling issue on cpu=94 
timer-softirq=279
[  526.960818] rcu: rcu_sched kthread starved for 5302 jiffies! g5989 
f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=94
[  526.981300] rcu:     Unless rcu_sched kthread gets sufficient CPU 
time, OOM is now expected behavior.
[  526.999182] rcu: RCU grace-period kthread stack dump:
[  527.009301] rcu: Stack dump where RCU GP kthread last ran:
[  548.035259] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
[  548.046861] rcu:     8-...!: (807 GPs behind) idle=071c/0/0x1 
softirq=682/682 fqs=0
[  548.061608] rcu:     17-...!: (0 ticks this GP) idle=00e8/0/0x0 
softirq=812/812 fqs=0 (false positive?)
[  548.079831] rcu:     84-...!: (0 ticks this GP) idle=d2b0/0/0x0 
softirq=797/797 fqs=0 (false positive?)
[  548.098070] rcu:     89-...!: (771 GPs behind) idle=7be8/0/0x0 
softirq=270/273 fqs=0 (false positive?)
[  548.116122] rcu:     112-...!: (226 GPs behind) idle=c110/0/0x0 
softirq=193/193 fqs=0 (false positive?)
[  548.134342] rcu:     185-...!: (0 ticks this GP) idle=45b8/0/0x0 
softirq=871/871 fqs=0 (false positive?)
[  548.152759] rcu:     193-...!: (0 ticks this GP) idle=1758/0/0x0 
softirq=1520/1520 fqs=0 (false positive?)
[  548.171509] rcu:     205-...!: (0 ticks this GP) idle=1e98/0/0x0 
softirq=852/852 fqs=0 (false positive?)
[  548.189893] rcu:     219-...!: (226 GPs behind) idle=d5c8/0/0x0 
softirq=605/607 fqs=0 (false positive?)
[  548.208128] rcu:     226-...!: (234 GPs behind) idle=eff0/0/0x0 
softirq=1189/1190 fqs=0 (false positive?)
[  548.226699] rcu:     (detected by 115, t=5300 jiffies, g=5993, q=5539 
ncpus=256)
[  548.241699] rcu: rcu_sched kthread timer wakeup didn't happen for 
5303 jiffies! g5993 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
[  548.263704] rcu:     Possible timer handling issue on cpu=94 
timer-softirq=279
[  548.277593] rcu: rcu_sched kthread starved for 5311 jiffies! g5993 
f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=94
[  548.298081] rcu:     Unless rcu_sched kthread gets sufficient CPU 
time, OOM is now expected behavior.
[  548.315971] rcu: RCU grace-period kthread stack dump:
[  548.326084] rcu: Stack dump where RCU GP kthread last ran:
[  569.343268] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
[  569.354868] rcu:     8-...!: (808 GPs behind) idle=07ac/0/0x1 
softirq=682/682 fqs=0
[  569.369617] rcu:     89-...!: (772 GPs behind) idle=8518/0/0x0 
softirq=270/273 fqs=0 (false positive?)
[  569.387674] rcu:     112-...!: (227 GPs behind) idle=c168/0/0x0 
softirq=193/193 fqs=0 (false positive?)
[  569.405894] rcu:     219-...!: (227 GPs behind) idle=d620/0/0x0 
softirq=605/607 fqs=0 (false positive?)
[  569.424128] rcu:     226-...!: (235 GPs behind) idle=f920/0/0x0 
softirq=1189/1190 fqs=0 (false positive?)
[  569.442700] rcu:     (detected by 76, t=5276 jiffies, g=5997, q=5665 
ncpus=256)
[  569.457146] rcu: rcu_sched kthread timer wakeup didn't happen for 
5278 jiffies! g5997 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
[  569.479149] rcu:     Possible timer handling issue on cpu=94 
timer-softirq=279
[  569.493043] rcu: rcu_sched kthread starved for 5285 jiffies! g5997 
f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=94
[  569.513534] rcu:     Unless rcu_sched kthread gets sufficient CPU 
time, OOM is now expected behavior.
[  569.531419] rcu: RCU grace-period kthread stack dump:
[  569.541536] rcu: Stack dump where RCU GP kthread last ran:
[  590.563260] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
[  590.574870] rcu:     8-...!: (809 GPs behind) idle=0824/0/0x1 
softirq=682/682 fqs=0
[  590.589618] rcu:     89-...!: (773 GPs behind) idle=8850/0/0x0 
softirq=270/273 fqs=0 (false positive?)
[  590.607682] rcu:     112-...!: (228 GPs behind) idle=c198/0/0x0 
softirq=193/193 fqs=0 (false positive?)
[  590.625904] rcu:     195-...!: (0 ticks this GP) idle=7178/0/0x0 
softirq=1038/1038 fqs=0 (false positive?)
[  590.644660] rcu:     207-...!: (0 ticks this GP) idle=9440/0/0x0 
softirq=809/809 fqs=0 (false positive?)
[  590.663056] rcu:     219-...!: (228 GPs behind) idle=d650/0/0x0 
softirq=605/607 fqs=0 (false positive?)
[  590.681285] rcu:     226-...!: (236 GPs behind) idle=fc78/0/0x0 
softirq=1189/1190 fqs=0 (false positive?)
[  590.699859] rcu:     (detected by 138, t=5286 jiffies, g=6001, q=5524 
ncpus=256)
[  590.714623] rcu: rcu_sched kthread timer wakeup didn't happen for 
5288 jiffies! g6001 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
[  590.736635] rcu:     Possible timer handling issue on cpu=94 
timer-softirq=279
[  590.750524] rcu: rcu_sched kthread starved for 5296 jiffies! g6001 
f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=94
[  590.771021] rcu:     Unless rcu_sched kthread gets sufficient CPU 
time, OOM is now expected behavior.
[  590.788903] rcu: RCU grace-period kthread stack dump:
[  590.799012] rcu: Stack dump where RCU GP kthread last ran:
[  606.363275] INFO: task kworker/u1024:0:12 blocked for more than 483 
seconds.
[  606.377139]       Tainted: G        W  7.1.0-rc2-test01 #1
[  606.389636] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" 
disables this message.
[  611.823259] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
[  611.834860] rcu:     8-...!: (810 GPs behind) idle=08bc/0/0x1 
softirq=682/682 fqs=0
[  611.849612] rcu:     89-...!: (774 GPs behind) idle=91a8/0/0x0 
softirq=270/273 fqs=0 (false positive?)
[  611.867665] rcu:     112-...!: (229 GPs behind) idle=c1d8/0/0x0 
softirq=193/193 fqs=0 (false positive?)
[  611.885887] rcu:     205-...!: (0 ticks this GP) idle=2160/0/0x0 
softirq=865/865 fqs=0 (false positive?)
[  611.904290] rcu:     219-...!: (229 GPs behind) idle=d690/0/0x0 
softirq=605/607 fqs=0 (false positive?)
[  611.922525] rcu:     226-...!: (237 GPs behind) idle=05e0/0/0x0 
softirq=1189/1190 fqs=0 (false positive?)
[  611.941095] rcu:     (detected by 166, t=5283 jiffies, g=6005, q=5522 
ncpus=256)
[  611.955789] rcu: rcu_sched kthread timer wakeup didn't happen for 
5285 jiffies! g6005 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
[  611.977793] rcu:     Possible timer handling issue on cpu=94 
timer-softirq=279
[  611.991685] rcu: rcu_sched kthread starved for 5292 jiffies! g6005 
f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=94
[  612.012174] rcu:     Unless rcu_sched kthread gets sufficient CPU 
time, OOM is now expected behavior.
[  612.030060] rcu: RCU grace-period kthread stack dump:
[  612.040180] rcu: Stack dump where RCU GP kthread last ran:

r[  727.195272] INFO: task kworker/u1024:0:12 blocked for more than 604 
seconds.
[  727.209134]       Tainted: G        W  7.1.0-rc2-test01 #1
[  727.221628] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" 
disables this message.

NOTE(S): Random hangs and same messages as S7-2. Takes about 15 minutes 
to see the messages.
---------------------------------------------------------
B2) SPARC64 T7-1 Kernel v7.0.4
[  OK  ] Finished e2scrub_reap.service - Remove Stale Online ext4 
Metadata Check Snapshots.

Debian GNU/Linux forky/sid s7t7-debian-test ttyHV0

s7t7-debian-test login: tonyr
Password:
Linux s7t7-debian-test 7.0.4-test01 #1 SMP Fri May  8 09:27:58 PDT 2026 
sparc64
[..]
Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
[   79.468871] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
[   79.480483] rcu:     114-...!: (424 GPs behind) idle=8760/0/0x0 
softirq=126/126 fqs=0 (false positive?)
[   79.498713] rcu:     (detected by 90, t=5259 jiffies, g=3769, q=818 
ncpus=256)
[   79.512702] rcu: rcu_sched kthread timer wakeup didn't happen for 
5260 jiffies! g3769 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
[   79.534808] rcu:     Possible timer handling issue on cpu=2 
timer-softirq=330
[   79.548516] rcu: rcu_sched kthread starved for 5267 jiffies! g3769 
f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=2
[   79.568838] rcu:     Unless rcu_sched kthread gets sufficient CPU 
time, OOM is now expected behavior.
[   79.586709] rcu: RCU grace-period kthread stack dump:
[   79.596867] rcu: Stack dump where RCU GP kthread last ran:
[  100.612874] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
[  100.624477] rcu:     114-...!: (425 GPs behind) idle=88f0/0/0x0 
softirq=126/126 fqs=0 (false positive?)
[  100.642709] rcu:     157-...!: (0 ticks this GP) idle=4c08/0/0x0 
softirq=122/122 fqs=0 (false positive?)
[  100.661106] rcu:     (detected by 3, t=5264 jiffies, g=3773, q=1046 
ncpus=256)
[  100.675155] rcu: rcu_sched kthread timer wakeup didn't happen for 
5265 jiffies! g3773 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
[  100.697211] rcu:     Possible timer handling issue on cpu=2 
timer-softirq=330
[  100.710934] rcu: rcu_sched kthread starved for 5276 jiffies! g3773 
f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=2
[  100.731244] rcu:     Unless rcu_sched kthread gets sufficient CPU 
time, OOM is now expected behavior.
[  100.749125] rcu: RCU grace-period kthread stack dump:
[  100.759255] rcu: Stack dump where RCU GP kthread last ran:
login: ti[  121.776867] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
[  121.788467] rcu:     114-...!: (426 GPs behind) idle=8a20/0/0x0 
softirq=126/126 fqs=0 (false positive?)
[  121.806703] rcu:     (detected by 3, t=5259 jiffies, g=3777, q=1267 
ncpus=256)
[  121.820664] rcu: rcu_sched kthread timer wakeup didn't happen for 
5260 jiffies! g3777 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
[  121.842799] rcu:     Possible timer handling issue on cpu=2 
timer-softirq=330
[  121.856521] rcu: rcu_sched kthread starved for 5271 jiffies! g3777 
f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=2
[  121.876836] rcu:     Unless rcu_sched kthread gets sufficient CPU 
time, OOM is now expected behavior.
[  121.894717] rcu: RCU grace-period kthread stack dump:
[  121.904824] rcu: Stack dump where RCU GP kthread last ran:
[  142.920877] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
[  142.932481] rcu:     114-...!: (427 GPs behind) idle=8b98/0/0x0 
softirq=126/126 fqs=0 (false positive?)
[  142.950709] rcu:     158-...!: (1 GPs behind) idle=5220/0/0x0 
softirq=142/148 fqs=0 (false positive?)
[  142.968586] rcu:     (detected by 122, t=5260 jiffies, g=3781, q=722 
ncpus=256)
[  142.982808] rcu: rcu_sched kthread timer wakeup didn't happen for 
5265 jiffies! g3781 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
[  143.004857] rcu:     Possible timer handling issue on cpu=2 
timer-softirq=330
[  143.018583] rcu: rcu_sched kthread starved for 5273 jiffies! g3781 
f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=2
[  143.038893] rcu:     Unless rcu_sched kthread gets sufficient CPU 
time, OOM is now expected behavior.
[  143.056761] rcu: RCU grace-period kthread stack dump:
[  143.066898] rcu: Stack dump where RCU GP kthread last ran:
[  164.084863] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
[  164.096463] rcu:     14-...!: (0 ticks this GP) idle=56b0/0/0x0 
softirq=165/165 fqs=0 (false positive?)
[  164.114695] rcu:     114-...!: (428 GPs behind) idle=8ed0/0/0x0 
softirq=126/126 fqs=0 (false positive?)
[  164.132916] rcu:     (detected by 96, t=5264 jiffies, g=3785, q=750 
ncpus=256)
[  164.146969] rcu: rcu_sched kthread timer wakeup didn't happen for 
5265 jiffies! g3785 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
[  164.169019] rcu:     Possible timer handling issue on cpu=2 
timer-softirq=330
[  164.182728] rcu: rcu_sched kthread starved for 5276 jiffies! g3785 
f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=2
[  164.203055] rcu:     Unless rcu_sched kthread gets sufficient CPU 
time, OOM is now expected behavior.
[  164.220922] rcu: RCU grace-period kthread stack dump:
[  164.231039] rcu: Stack dump where RCU GP kthread last ran:
[  185.248867] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
[  185.260468] rcu:     21-...!: (0 ticks this GP) idle=36c8/0/0x0 
softirq=154/154 fqs=0 (false positive?)
[  185.278684] rcu:     114-...!: (429 GPs behind) idle=8f68/0/0x0 
softirq=126/126 fqs=0 (false positive?)
[  185.296922] rcu:     (detected by 116, t=5264 jiffies, g=3789, q=760 
ncpus=256)
[  185.311140] rcu: rcu_sched kthread timer wakeup didn't happen for 
5265 jiffies! g3789 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
[  185.333205] rcu:     Possible timer handling issue on cpu=2 
timer-softirq=330
[  185.346918] rcu: rcu_sched kthread starved for 5276 jiffies! g3789 
f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=2
[  185.367224] rcu:     Unless rcu_sched kthread gets sufficient CPU 
time, OOM is now expected behavior.
[  185.385113] rcu: RCU grace-period kthread stack dump:
[  185.395229] rcu: Stack dump where RCU GP kthread last ran:
  OK  ] Reached target network-online.target - Network is Online.
[  OK  ] Started anacron.service - Run anacron jobs.
[  OK  ] Started cups-browsed.service - Make remote CUPS printers 
available locally.
         Starting exim4.service - exim Mail Transport Agent...
         Starting xrdp.service - xrdp daemon...
[  OK  ] Finished user-runtime-dir@1000.service - User Runtime Directory 
/run/user/1000.
[  OK  ] Started xrdp.service - xrdp daemon.
[  OK  ] Started serial-getty@ttyHV0.service - Serial Getty on ttyHV0.
         Starting user@1000.service - User Manager for UID 1000...
[  OK  ] Started exim4.service - exim Mail Transport Agent.
[  OK  ] Reached target multi-user.target - Multi-User System.
[  OK  ] Reached target graphical.target - Graphical Interface.
[  OK  ] Started user@1000.service - User Manager for UID 1000.
[FAILED] Failed to start session-1.scope - Session 1 of User tonyr.
See 'systemctl status session-1.scope' for details.
[  206.412865] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
[  206.424477] rcu:     114-...!: (430 GPs behind) idle=97b0/0/0x0 
softirq=126/126 fqs=0 (false positive?)
[  206.442691] rcu:     (detected by 123, t=5259 jiffies, g=3793, q=5473 
ncpus=256)
[  206.457056] rcu: rcu_sched kthread timer wakeup didn't happen for 
5261 jiffies! g3793 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
[  206.479157] rcu:     Possible timer handling issue on cpu=2 
timer-softirq=330
[  206.492868] rcu: rcu_sched kthread starved for 5271 jiffies! g3793 
f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=2
[  206.513173] rcu:     Unless rcu_sched kthread gets sufficient CPU 
time, OOM is now expected behavior.
[  206.531061] rcu: RCU grace-period kthread stack dump:
[  206.541202] rcu: Stack dump where RCU GP kthread last ran:

NOTE(S): Unable to login and random hangs during system startup. Same 
messages/issues as S7-2.


On 5/8/26 12:50 AM, Thorsten Leemhuis wrote:
> [+tglx so he knows about it; details about the problem that Tony faces
> can be found in https://github.com/sparclinux/issues/issues/79 ]
>
> On 5/8/26 09:38, Tony Rodriguez wrote:
> > I still don't believe this is fixed upstream as of v7.03 and v7.1-rc1,
> Yes and no. It looks like d6e152d905bdb1 ("clockevents: Prevent timer
> interrupt starvation") causes two regression.
>
> Thomas fixed one with 4096fd0e8eaea1 ("clockevents: Add missing resets
> of the next_event_forced flag") -- and feedback shows that it definitely
> solved the problem for quite a few people. If that's not the case for
> you, then you seem to face a different problem caused by the same
> change. Happens, that's life sometimes.
>
> Ciao, Thorsten
>
> > only when my patch is applied does the SPARC74 S7-2 system become stable
> > again. I also tested my patch with v7.0.4 and it works their as well.
> > Will perform additional tests without my fix against v7.0.4 and v7.1-rc2
> > later today to revalidate the regression (USA Pacific time).
> >
> > Tony Rodriguez
> > www.linkedin.com/in/unixpro1970
> >
> > > On May 7, 2026, at 11:33 PM, Thorsten Leemhuis <linux@xxxxxxxxxxxxx>
> > > wrote:
> > >
> > > On 5/8/26 07:51, John Paul Adrian Glaubitz wrote:
> > > > On Thu, 2026-04-23 at 18:30 +0200, Thorsten Leemhuis wrote:
> > > > > FWIW, here is the rough timeline of the regression, just to be sure we
> > > > > are all on the same page:
> > > > >
> > > > > * The regression I'm talking about is caused by d6e152d905bdb1
> > > > > ("clockevents: Prevent timer interrupt starvation") [authored:
> > > > > 2026-04-07 10:54:17; committed: 2026-04-10 22:45:38; next arrival:
> > > > > next-20260413; merged: 2026-04-12 19:01:55; v7.0 (2026-04-12 22:48:06)]
> > > > [...]
> > > > Tony Rodriguez from the SPARC community has observed the regression
> > > > on SPARC as well
> > > > and proposed a fix to address it [1]. Not sure whether he has
> > > > retested on the latest
> > > > commit of Linus' tree yet.
> > > >
> > > > Tony, can you verify that 4096fd0e8eaea1 fixes the issue for you?
> > > >
> > > > > [1] https://github.com/sparclinux/issues/issues/79
> > > It's likely a different regressions, as that report's title says that
> > > v7.0.1, v7.0.2, v7.0.3, and v7.1‑rc1 are affected, which all contain the
> > > fix, aka 4096fd0e8eaea1. Reporting in a new thread is likely best, as
> > > the authors of the culprit are not even CCed here.
> > >
> > > Ciao, Thorsten