Paul,
Michael J. Sullivan from our performance team told me that
commit 9111b9361f2 EXP: Fine-grained timer diagnostics breaks cpu hot unplug for him.
I can confirm that.
A crash dump show (minus the removed CPU) the following:
[cborntra@s38lp08 linux]$ cat e
PID: 0 TASK: c41800 CPU: 0 COMMAND: "swapper/0"
LOWCORE INFO:
-psw : 0x0404e00180000000 0x0000000000850226
-function : arch_spin_lock_wait at 850226
-prefix : 0x7fffc000
-cpu timer: 0x7fffffece131fc54
-clock cmp: 0x42e72b784707c600
#0 [7fffbbf8] lock_timer_base at 1e4d22
#1 [7fffbc60] mod_timer at 1e5f2c
#2 [7fffbcd0] __sclp_start_request at 6aabae
#3 [7fffbcf8] sclp_process_queue at 6abae0
#4 [7fffbd38] do_ext_interrupt at 10b90e
#5 [7fffbd80] __handle_irq_event_percpu at 1cb590
#6 [7fffbdf0] handle_irq_event_percpu at 1cb746
#7 [7fffbe28] handle_percpu_irq at 1d04a4
#8 [7fffbe58] generic_handle_irq at 1ca53a
#9 [7fffbe70] do_IRQ at 10bd2e
#10 [7fffbea8] ext_int_handler at 85b2c4
PSW: 0404c00180000000 0000000000102bfe (enabled_wait+78)
GPRS: d342e71c70aa3658 0000000000000000 000000007ff5a200 0706c00180000000
00000000001b3f20 000000000086e4a0 ffffffffffffffff 0000000000000000
0000000000000000 0000000000000000 0000000000000000 0000000000d790b8
000000007ff5a200 0000000000860348 0000000000102bfe 0000000000c2fe48
#0 [00c2fe70] arch_cpu_idle at 102f52
#1 [00c2fe90] do_idle at 1b3f3a
#2 [00c2feb8] cpu_startup_entry at 1b4176
#3 [00c2fee0] start_kernel at d24bd8
#4 [00c2ff60] _stext at 100020
PID: 0 TASK: 7d8eb600 CPU: 1 COMMAND: "swapper/1"
LOWCORE INFO:
-psw : 0x0404c00180000000 0x00000000001163a6
-function : smp_yield_cpu at 1163a6
-prefix : 0x7d756000
-cpu timer: 0x7fffffece146c32a
-clock cmp: 0x42e7215bd6c88e00
#0 [7d75bcb0] arch_spin_lock_wait at 850298
#1 [7d75bd08] sclp_interrupt_handler at 6abeda
#2 [7d75bd38] do_ext_interrupt at 10b90e
#3 [7d75bd80] __handle_irq_event_percpu at 1cb590
#4 [7d75bdf0] handle_irq_event_percpu at 1cb746
#5 [7d75be28] handle_percpu_irq at 1d04a4
#6 [7d75be58] generic_handle_irq at 1ca53a
#7 [7d75be70] do_IRQ at 10bd2e
#8 [7d75bea8] ext_int_handler at 85b2c4
PSW: 0404c00180000000 0000000000102bfe (enabled_wait+78)
GPRS: 0000000003247e88 0000000000000000 000000007ff71200 0706c00180000000
00000000001b3f20 000000000086e4a0 0000000000000000 0000000000000000
0000000000000000 0000000000000000 0000000000000000 0000000000000001
000000007ff71200 0000000000860348 0000000000102bfe 000000007d8ffc78
#0 [7d8ffca0] arch_cpu_idle at 102f52
#1 [7d8ffcc0] do_idle at 1b3f3a
#2 [7d8ffce8] cpu_startup_entry at 1b4176
#3 [7d8ffd10] smp_start_secondary at 115d96
#4 [7d8ffd50] restart_int_handler at 85b60a
PID: 84 TASK: 3305a00 CPU: 2 COMMAND: "sh"
LOWCORE INFO:
-psw : 0x0404c00180000000 0x00000000001163a6
-function : smp_yield_cpu at 1163a6
-prefix : 0x7d780000
-cpu timer: 0x7fffffecf69f4974
-clock cmp: 0x42e71c731cb22c00
#0 [033476e0] arch_spin_lock_wait at 850298
#1 [03347738] lock_timer_base at 1e4d22
#2 [033477a0] mod_timer at 1e5f2c
#3 [03347810] __sclp_vt220_write at 6ba912
#4 [033478a0] sclp_vt220_con_write at 6ba9ac
#5 [033478f8] console_unlock at 1c87c8
#6 [03347978] vprintk_emit at 1c8bbe
#7 [03347a08] vprintk_default at 1c8e1c
#8 [03347a68] printk at 1c9d1e
#9 [03347af8] timers_dead_cpu at 1e66f6
#10 [03347b68] cpuhp_invoke_callback at 169b50
#11 [03347c00] _cpu_down at 851522
#12 [03347c58] do_cpu_down at 16b9fa
#13 [03347c88] device_offline at 5a7826
#14 [03347cc0] online_store at 5a796e
#15 [03347cf8] kernfs_fop_write at 3ed8d2
#16 [03347d48] __vfs_write at 34ddb6
#17 [03347e00] vfs_write at 34e10c
#18 [03347e60] sys_write at 34e44e
#19 [03347ea8] system_call at 85abf4
Reverting the patch fixes the issue, but I do not yet understand why.
Christian
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