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

From: Tony Rodriguez

Date: Fri May 08 2026 - 16:24:35 EST

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. I 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 SPARC64 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