Re: [lkp-robot] [torture] b151f93a71: INFO:rcu_preempt_detected_stalls_on_CPUs/tasks

Paul E. McKenney
2017-11-28T20:46:27Z

On Tue, Nov 28, 2017 at 09:35:54AM -0800, Paul E. McKenney wrote:
> On Tue, Nov 28, 2017 at 06:10:08PM +0100, Thomas Gleixner wrote:
> > On Tue, 28 Nov 2017, Paul E. McKenney wrote:
> > > On Tue, Nov 28, 2017 at 05:47:35PM +0100, Thomas Gleixner wrote:
> > > diff --git a/kernel/time/timer.c b/kernel/time/timer.c
> > > index db774b0f217e..a3321bb565db 100644
> > > --- a/kernel/time/timer.c
> > > +++ b/kernel/time/timer.c
> > > @@ -1803,7 +1803,7 @@ signed long __sched schedule_timeout(signed long timeout)
> > > idx = timer_get_idx(&timer.timer);
> > > idx_now = calc_wheel_index(j, base->clk);
> > > raw_spin_unlock_irqrestore(&base->lock, flags);
> > > - pr_info("%s: Waylayed timer idx: %u idx_now: %u\n", __func__, idx, idx_now);
> > > + pr_info("%s: Waylayed timer base->clk: %#lx jiffies: %#lx base->next_expiry: %#lx timer->flags: %#x timer->expires %#lx idx: %u idx_now: %u\n", __func__, base->clk, j, base->next_expiry, timer.timer.flags, timer.timer.expires, idx, idx_now);
> >
> > Please print idx and idx_now as hex values. It's simpler to decode that way.
>
> Here you go! Starting tests at this end, focusing on TREE01 and TREE04.
> BTW, TREE04 doesn't do any CPU hotplug, providing a counterexample to
> my long-held assumption that this only happened in the presence of CPU
> hotplug operations.

And here is output with changes discussed on IRC. TREE04 managed to
have not one but two overlapping RCU CPU stall warnings, one for RCU-bh
and the second for RCU-sched. TREE04 and TREE04. HZ=1000.

------------------------------------------------------------------------
TREE04
------------------------------------------------------------------------

[ 28.336052] INFO: rcu_bh detected stalls on CPUs/tasks:
[ 28.347354] 1-...!: (14 ticks this GP) idle=c2a/1/4611686018427387904 softirq=0/0 fqs=3 last_accelerate: 0000/dad0, nonlazy_posted: 0, LD
[ 28.349312] 2-...!: (81 GPs behind) idle=892/1/4611686018427387904 softirq=0/0 fqs=3 last_accelerate: 0000/dad0, nonlazy_posted: 0, LD
[ 28.351338] 3-...!: (11 GPs behind) idle=31e/1/4611686018427387904 softirq=0/0 fqs=3 last_accelerate: 0000/dad0, nonlazy_posted: 0, LD
[ 28.353177] 4-...!: (81 GPs behind) idle=dd6/1/4611686018427387904 softirq=0/0 fqs=3 last_accelerate: 0000/dad0, nonlazy_posted: 0, LD
[ 28.354966] 5-...!: (81 GPs behind) idle=cbe/1/4611686018427387904 softirq=0/0 fqs=3 last_accelerate: 0000/dad0, nonlazy_posted: 0, LD
[ 28.356866] 7-...!: (81 GPs behind) idle=fa2/1/4611686018427387904 softirq=0/0 fqs=3 last_accelerate: 0000/dad0, nonlazy_posted: 0, LD
[ 28.358698] (detected by 0, t=21002 jiffies, g=-219, c=-220, q=0)
[ 28.359697] Sending NMI from CPU 0 to CPUs 1:
[ 28.360694] NMI backtrace for cpu 1
[ 28.360897] CPU: 1 PID: 771 Comm: rcu_torture_rea Not tainted 4.15.0-rc1+ #1
[ 28.360899] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
[ 28.360923] task: ffff95965de172c0 task.stack: ffffa09d80bcc000
[ 28.361249] RIP: 0010:delay_tsc+0x30/0x50
[ 28.361250] RSP: 0018:ffffa09d80bcfe50 EFLAGS: 00000206
[ 28.361253] RAX: 000000100247c65a RBX: 000000000000000d RCX: 0000000000084130
[ 28.361254] RDX: 0000001000000000 RSI: 00000010023f852a RDI: 00000000001e717e
[ 28.361256] RBP: ffffa09d80bcfe90 R08: 0000000000000001 R09: 0000000000000101
[ 28.361257] R10: 0000000000000000 R11: ffffa09d80bcfe58 R12: 0000000001b42b8a
[ 28.361259] R13: ffffffffffffff24 R14: 00000006a7ca1638 R15: ffffffffffffff25
[ 28.361261] FS: 0000000000000000(0000) GS:ffff95965fc40000(0000) knlGS:0000000000000000
[ 28.361267] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 28.361269] CR2: 0000000008d98b40 CR3: 000000000820a000 CR4: 00000000000006e0
[ 28.361269] Call Trace:
[ 28.361604] rcu_read_delay+0xab/0xf0
[ 28.361809] rcu_torture_reader+0x175/0x2e0
[ 28.361837] ? rcu_torture_reader+0x2e0/0x2e0
[ 28.361864] ? kthread+0xf0/0x130
[ 28.361866] kthread+0xf0/0x130
[ 28.361938] ? rcu_torture_timer_cb+0x10/0x10
[ 28.361940] ? kthread_destroy_worker+0x40/0x40
[ 28.362012] ? call_usermodehelper_exec_async+0x11c/0x120
[ 28.362059] ret_from_fork+0x1f/0x30
[ 28.362106] Code: 03 10 5a 0f ae e8 0f 31 48 c1 e2 20 48 89 d6 48 09 c6 0f ae e8 0f 31 48 c1 e2 20 48 09 d0 48 89 c1 48 29 f1 48 39 cf 76 19 f3 90 <65> 8b 0d f9 02 10 5a 41 39 c8 74 db 48 29 c6 41 89 c8 48 01 f7
[ 28.362281] INFO: NMI handler (nmi_cpu_backtrace_handler) took too long to run: 1.540 msecs
[ 28.362458] Sending NMI from CPU 0 to CPUs 2:
[ 28.362489] NMI backtrace for cpu 2
[ 28.362512] CPU: 2 PID: 775 Comm: rcu_torture_rea Not tainted 4.15.0-rc1+ #1
[ 28.362513] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
[ 28.362515] task: ffff95965e348000 task.stack: ffffa09d8151c000
[ 28.362519] RIP: 0010:kthread_should_stop+0x0/0x30
[ 28.362520] RSP: 0000:ffffa09d8151fe70 EFLAGS: 00000246
[ 28.362523] RAX: 0000000000000001 RBX: ffffffffa7b79a60 RCX: 000000000000000a
[ 28.362524] RDX: 0000000000000000 RSI: 00000000fffffe01 RDI: ffffffffa61d6272
[ 28.362525] RBP: ffffa09d8151ff00 R08: 0000000000000002 R09: 0000000000000101
[ 28.362527] R10: 0000000000000000 R11: ffffa09d8151fe58 R12: ffffffffffffff24
[ 28.362528] R13: 0000000000000000 R14: 00000006aa8d6d83 R15: ffffffffffffff25
[ 28.362530] FS: 0000000000000000(0000) GS:ffff95965fc80000(0000) knlGS:0000000000000000
[ 28.362543] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 28.362548] CR2: 0000000000000000 CR3: 000000000820a000 CR4: 00000000000006e0
[ 28.362549] Call Trace:
[ 28.362585] torture_must_stop+0x16/0x20
[ 28.362607] rcu_torture_reader+0xf4/0x2e0
[ 28.362611] ? rcu_torture_reader+0x2e0/0x2e0
[ 28.362613] ? kthread+0xf0/0x130
[ 28.362615] kthread+0xf0/0x130
[ 28.362618] ? rcu_torture_timer_cb+0x10/0x10
[ 28.362620] ? kthread_destroy_worker+0x40/0x40
[ 28.362623] ret_from_fork+0x1f/0x30
[ 28.362625] Code: 90 66 2e 0f 1f 84 00 00 00 00 00 48 8b 4f 40 48 89 d0 be 00 10 00 00 48 c7 c2 e0 6b 1c a6 48 89 c7 e8 65 a8 89 00 48 98 c3 90 90 <65> 48 8b 04 25 00 c4 00 00 f6 40 4e 20 74 11 48 8b 80 b8 05 00
[ 28.363476] Sending NMI from CPU 0 to CPUs 3:
[ 28.363509] NMI backtrace for cpu 3
[ 28.363529] CPU: 3 PID: 774 Comm: rcu_torture_rea Not tainted 4.15.0-rc1+ #1
[ 28.363530] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
[ 28.363532] task: ffff95965e34f2c0 task.stack: ffffa09d81514000
[ 28.363547] RIP: 0010:native_sched_clock+0x28/0x70
[ 28.363548] RSP: 0000:ffffa09d81517e70 EFLAGS: 00000a47
[ 28.363549] RAX: 033b0c542f257800 RBX: ffffffffa7b79a60 RCX: 0000000000000000
[ 28.363550] RDX: 0000000000000004 RSI: 0000000040291878 RDI: 0000000000000001
[ 28.363551] RBP: ffffa09d81517f00 R08: 0000000000000003 R09: 0000000000000101
[ 28.363552] R10: 0000000000000000 R11: ffffa09d81517e58 R12: ffffffffffffff24
[ 28.363553] R13: 0000000000000000 R14: 00000006aa9cf9f2 R15: ffffffffffffff25
[ 28.363554] FS: 0000000000000000(0000) GS:ffff95965fcc0000(0000) knlGS:0000000000000000
[ 28.363558] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 28.363559] CR2: 0000000000000000 CR3: 000000000820a000 CR4: 00000000000006e0
[ 28.363561] Call Trace:
[ 28.363582] trace_clock_local+0x5/0x10
[ 28.363598] rcu_torture_reader+0x146/0x2e0
[ 28.363602] ? rcu_torture_reader+0x2e0/0x2e0
[ 28.363605] ? kthread+0xf0/0x130
[ 28.363606] kthread+0xf0/0x130
[ 28.363608] ? rcu_torture_timer_cb+0x10/0x10
[ 28.363610] ? kthread_destroy_worker+0x40/0x40
[ 28.363616] ret_from_fork+0x1f/0x30
[ 28.363618] Code: 00 00 00 0f 1f 44 00 00 0f 31 48 c1 e2 20 48 09 c2 65 8b 0d cb 67 9f 5a 83 e1 01 48 c1 e1 04 65 8b b1 80 77 01 00 89 f0 48 f7 e2 <65> 48 8b b9 88 77 01 00 48 81 c1 80 77 01 00 65 8b 49 04 48 0f
[ 28.364496] Sending NMI from CPU 0 to CPUs 4:
[ 28.364558] NMI backtrace for cpu 4
[ 28.364580] CPU: 4 PID: 776 Comm: rcu_torture_rea Not tainted 4.15.0-rc1+ #1
[ 28.364581] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
[ 28.364583] task: ffff95965e349980 task.stack: ffffa09d81524000
[ 28.364594] RIP: 0010:rcu_read_delay+0x21/0xf0
[ 28.364595] RSP: 0000:ffffa09d81527e58 EFLAGS: 00000246
[ 28.364596] RAX: 00000000000011b7 RBX: ffffffffa7b79a60 RCX: 00000000000aae60
[ 28.364597] RDX: 000000000004121f RSI: 0000000000000001 RDI: ffffa09d81527e90
[ 28.364598] RBP: ffffa09d81527e90 R08: 0000000000000004 R09: 0000000000000001
[ 28.364599] R10: 0000000000000000 R11: 0000000000000000 R12: ffffffffffffff24
[ 28.364600] R13: 0000000000000000 R14: 00000006aaac8262 R15: ffffffffffffff25
[ 28.364602] FS: 0000000000000000(0000) GS:ffff95965fd00000(0000) knlGS:0000000000000000
[ 28.364606] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 28.364607] CR2: 0000000000000000 CR3: 000000000820a000 CR4: 00000000000006e0
[ 28.364608] Call Trace:
[ 28.364615] rcu_torture_reader+0x175/0x2e0
[ 28.364618] ? rcu_torture_reader+0x2e0/0x2e0
[ 28.364622] ? kthread+0xf0/0x130
[ 28.364623] kthread+0xf0/0x130
[ 28.364625] ? rcu_torture_timer_cb+0x10/0x10
[ 28.364626] ? kthread_destroy_worker+0x40/0x40
[ 28.364633] ret_from_fork+0x1f/0x30
[ 28.364635] Code: 7c 0a ff ff e9 d4 fe ff ff 90 41 55 41 54 55 53 48 89 fd e8 d2 14 08 00 48 63 0d ff 5f 4d 02 31 d2 48 69 c9 a0 86 01 00 48 f7 f1 <48> 85 d2 74 4c 48 89 ef e8 b2 14 08 00 48 63 15 df 5f 4d 02 48
[ 28.365511] Sending NMI from CPU 0 to CPUs 5:
[ 28.365568] NMI backtrace for cpu 5
[ 28.365590] CPU: 5 PID: 777 Comm: rcu_torture_rea Not tainted 4.15.0-rc1+ #1
[ 28.365591] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
[ 28.365593] task: ffff95965e34b300 task.stack: ffffa09d8152c000
[ 28.365600] RIP: 0010:delay_tsc+0x30/0x50
[ 28.365601] RSP: 0000:ffffa09d8152fe50 EFLAGS: 00000206
[ 28.365604] RAX: 0000001002e258ec RBX: 0000000000000030 RCX: 00000000001b1080
[ 28.365605] RDX: 0000001000000000 RSI: 0000001002c7486c RDI: 00000000001e713d
[ 28.365606] RBP: ffffa09d8152fe90 R08: 0000000000000005 R09: 0000000000000101
[ 28.365608] R10: 0000000000000000 R11: ffffa09d8152fe58 R12: 0000000001b4e144
[ 28.365609] R13: ffffffffffffff24 R14: 00000006aa8ff1b1 R15: ffffffffffffff25
[ 28.365611] FS: 0000000000000000(0000) GS:ffff95965fd40000(0000) knlGS:0000000000000000
[ 28.365616] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 28.365617] CR2: 0000000000000000 CR3: 000000000820a000 CR4: 00000000000006e0
[ 28.365618] Call Trace:
[ 28.365626] rcu_read_delay+0xab/0xf0
[ 28.365631] rcu_torture_reader+0x175/0x2e0
[ 28.365634] ? rcu_torture_reader+0x2e0/0x2e0
[ 28.365638] ? kthread+0xf0/0x130
[ 28.365640] kthread+0xf0/0x130
[ 28.365643] ? rcu_torture_timer_cb+0x10/0x10
[ 28.365645] ? kthread_destroy_worker+0x40/0x40
[ 28.365650] ret_from_fork+0x1f/0x30
[ 28.365652] Code: 03 10 5a 0f ae e8 0f 31 48 c1 e2 20 48 89 d6 48 09 c6 0f ae e8 0f 31 48 c1 e2 20 48 09 d0 48 89 c1 48 29 f1 48 39 cf 76 19 f3 90 <65> 8b 0d f9 02 10 5a 41 39 c8 74 db 48 29 c6 41 89 c8 48 01 f7
[ 28.366528] Sending NMI from CPU 0 to CPUs 7:
[ 28.366582] NMI backtrace for cpu 7
[ 28.366606] CPU: 7 PID: 773 Comm: rcu_torture_rea Not tainted 4.15.0-rc1+ #1
[ 28.366607] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
[ 28.366609] task: ffff95965e34a640 task.stack: ffffa09d8150c000
[ 28.366613] RIP: 0010:delay_tsc+0x1a/0x50
[ 28.366615] RSP: 0000:ffffa09d8150fe50 EFLAGS: 00000246
[ 28.366617] RAX: 0000001003014a92 RBX: ffffffffa7b79a60 RCX: 0000000000000007
[ 28.366618] RDX: 0000001000000000 RSI: 0000001002fe3cda RDI: 000000000006169a
[ 28.366619] RBP: ffffa09d8150fe90 R08: 0000000000000007 R09: 0000000000000001
[ 28.366621] R10: 0000000000000000 R11: 0000000000000002 R12: ffffffffffffff24
[ 28.366622] R13: 0000000000000000 R14: 00000006aaca0452 R15: ffffffffffffff25
[ 28.366624] FS: 0000000000000000(0000) GS:ffff95965fdc0000(0000) knlGS:0000000000000000
[ 28.366629] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 28.366630] CR2: 0000000000000000 CR3: 000000000820a000 CR4: 00000000000006e0
[ 28.366631] Call Trace:
[ 28.366635] rcu_read_delay+0xe8/0xf0
[ 28.366639] rcu_torture_reader+0x175/0x2e0
[ 28.366642] ? rcu_torture_reader+0x2e0/0x2e0
[ 28.366644] ? kthread+0xf0/0x130
[ 28.366646] kthread+0xf0/0x130
[ 28.366648] ? rcu_torture_timer_cb+0x10/0x10
[ 28.366651] ? kthread_destroy_worker+0x40/0x40
[ 28.366654] ret_from_fork+0x1f/0x30
[ 28.366655] Code: 00 00 00 f7 e2 48 8d 7a 01 ff 25 e2 80 5f 00 66 90 65 44 8b 05 28 03 10 5a 0f ae e8 0f 31 48 c1 e2 20 48 89 d6 48 09 c6 0f ae e8 <0f> 31 48 c1 e2 20 48 09 d0 48 89 c1 48 29 f1 48 39 cf 76 19 f3
[ 28.367562] rcu_bh kthread starved for 21016 jiffies! g18446744073709551397 c18446744073709551396 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x402 ->cpu=1
[ 28.367567] rcu_bh I15008 9 2 0x80080000
[ 28.367589] Call Trace:
[ 28.367606] ? __schedule+0x316/0x6b0
[ 28.367607] schedule+0x2d/0x80
[ 28.367610] schedule_timeout+0x159/0x3f0
[ 28.367625] ? __next_timer_interrupt+0xc0/0xc0
[ 28.367629] rcu_gp_kthread+0x627/0xd90
[ 28.367646] ? migrate_swap_stop+0x160/0x180
[ 28.367649] kthread+0xf0/0x130
[ 28.367655] ? rcu_barrier_sched+0x10/0x10
[ 28.367657] ? kthread_destroy_worker+0x40/0x40
[ 28.367659] ret_from_fork+0x1f/0x30
[ 28.567094] schedule_timeout: Waylayed timer base->clk: 0xfffb88d4 jiffies: 0xfffbdbb7 base->next_expiry: 0xfffb88d4 timer->flags: 0x5800001 timer->expires 0xfffb88d5 idx: 16 idx_now: ee base->pending_map 500000 400000000000000 1000000000000 40 0 2 0 0 0
[ 30.330055] INFO: rcu_sched detected stalls on CPUs/tasks:
[ 30.331770] 1-...!: (88 GPs behind) idle=c36/1/4611686018427387904 softirq=0/0 fqs=0 last_accelerate: 0000/e29a, nonlazy_posted: 0, LD
[ 30.335218] 4-...!: (88 GPs behind) idle=de2/1/4611686018427387904 softirq=0/0 fqs=0 last_accelerate: 0000/e29a, nonlazy_posted: 0, LD
[ 30.337537] 5-...!: (88 GPs behind) idle=cca/1/4611686018427387904 softirq=0/0 fqs=0 last_accelerate: 0000/e29a, nonlazy_posted: 0, LD
[ 30.339869] 7-...!: (0 ticks this GP) idle=fae/1/4611686018427387904 softirq=0/0 fqs=0 last_accelerate: 0000/e29a, nonlazy_posted: 0, LD
[ 30.342199] (detected by 0, t=21002 jiffies, g=-212, c=-213, q=80)
[ 30.343442] Sending NMI from CPU 0 to CPUs 1:
[ 30.344302] NMI backtrace for cpu 1
[ 30.344328] CPU: 1 PID: 771 Comm: rcu_torture_rea Not tainted 4.15.0-rc1+ #1
[ 30.344329] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
[ 30.344331] task: ffff95965de172c0 task.stack: ffffa09d80bcc000
[ 30.344347] RIP: 0010:torture_random+0x0/0x50
[ 30.344348] RSP: 0018:ffffa09d80bcfe50 EFLAGS: 00000202
[ 30.344351] RAX: 0000000000000e40 RBX: ffffffffa7b79a60 RCX: 00000000000aae60
[ 30.344352] RDX: 000000000006afb0 RSI: 0000000000000001 RDI: ffffa09d80bcfe90
[ 30.344353] RBP: ffffa09d80bcfe90 R08: 0000000000000001 R09: 0000000000000101
[ 30.344355] R10: 0000000000000000 R11: ffffa09d80bcfe58 R12: ffffffffffffff27
[ 30.344356] R13: 0000000000000000 R14: 0000000720ada1cc R15: ffffffffffffff27
[ 30.344358] FS: 0000000000000000(0000) GS:ffff95965fc40000(0000) knlGS:0000000000000000
[ 30.344364] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 30.344365] CR2: 0000000008d98b40 CR3: 000000000820a000 CR4: 00000000000006e0
[ 30.344366] Call Trace:
[ 30.344381] rcu_read_delay+0x2e/0xf0
[ 30.344387] rcu_torture_reader+0x175/0x2e0
[ 30.344390] ? rcu_torture_reader+0x2e0/0x2e0
[ 30.344395] ? kthread+0xf0/0x130
[ 30.344396] kthread+0xf0/0x130
[ 30.344399] ? rcu_torture_timer_cb+0x10/0x10
[ 30.344401] ? kthread_destroy_worker+0x40/0x40
[ 30.344407] ? call_usermodehelper_exec_async+0x11c/0x120
[ 30.344416] ret_from_fork+0x1f/0x30
[ 30.344418] Code: 00 66 2e 0f 1f 84 00 00 00 00 00 31 c0 c3 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 8b 05 4a e0 d2 00 85 c0 0f 95 c0 c3 0f 1f 40 00 <48> 83 6f 08 01 78 14 48 69 07 01 15 61 02 48 05 65 fc 8c 1c 48
[ 30.345302] Sending NMI from CPU 0 to CPUs 4:
[ 30.345329] NMI backtrace for cpu 4
[ 30.345359] CPU: 4 PID: 776 Comm: rcu_torture_rea Not tainted 4.15.0-rc1+ #1
[ 30.345361] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
[ 30.345364] task: ffff95965e349980 task.stack: ffffa09d81524000
[ 30.345375] RIP: 0010:rcu_torture_reader+0xc5/0x2e0
[ 30.345376] RSP: 0000:ffffa09d81527e80 EFLAGS: 00000213
[ 30.345379] RAX: 0000000000000001 RBX: ffffffffa7b79a60 RCX: 000000000000000a
[ 30.345380] RDX: ffffffffa64462c0 RSI: 0000000000000001 RDI: ffffa09d81527e90
[ 30.345382] RBP: ffffa09d81527f00 R08: 0000000000000004 R09: ffff95965fd1a040
[ 30.345383] R10: 0000000000000000 R11: 0000000000000000 R12: ffffffffffffff27
[ 30.345384] R13: 0000000000000000 R14: 0000000720bd3427 R15: ffffffffffffff27
[ 30.345386] FS: 0000000000000000(0000) GS:ffff95965fd00000(0000) knlGS:0000000000000000
[ 30.345392] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 30.345393] CR2: 0000000000000000 CR3: 000000000820a000 CR4: 00000000000006e0
[ 30.345445] Call Trace:
[ 30.345455] ? rcu_torture_reader+0x2e0/0x2e0
[ 30.345459] ? kthread+0xf0/0x130
[ 30.345461] kthread+0xf0/0x130
[ 30.345464] ? rcu_torture_timer_cb+0x10/0x10
[ 30.345466] ? kthread_destroy_worker+0x40/0x40
[ 30.345473] ret_from_fork+0x1f/0x30
[ 30.345476] Code: f8 00 00 00 48 8b 15 53 51 4d 02 4c 89 e0 4d 63 d5 4c 29 f8 b9 0a 00 00 00 65 4a ff 04 d5 20 0f 01 00 48 83 7a 30 01 48 83 d8 ff <48> 83 f8 0a 48 0f 47 c1 65 48 ff 04 c5 c0 0e 01 00 48 8b 05 1b
[ 30.346316] Sending NMI from CPU 0 to CPUs 5:
[ 30.346336] NMI backtrace for cpu 5
[ 30.346358] CPU: 5 PID: 777 Comm: rcu_torture_rea Not tainted 4.15.0-rc1+ #1
[ 30.346359] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
[ 30.346361] task: ffff95965e34b300 task.stack: ffffa09d8152c000
[ 30.346369] RIP: 0010:delay_tsc+0x30/0x50
[ 30.346371] RSP: 0000:ffffa09d8152fe50 EFLAGS: 00000202
[ 30.346373] RAX: 00000010ee6c68c7 RBX: 000000000000001e RCX: 0000000000191a4c
[ 30.346374] RDX: 0000001000000000 RSI: 00000010ee534e7b RDI: 00000000001e713d
[ 30.346376] RBP: ffffa09d8152fe90 R08: 0000000000000005 R09: 0000000000000001
[ 30.346377] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000001d2d4b3
[ 30.346378] R13: ffffffffffffff27 R14: 000000071f8edc6b R15: ffffffffffffff27
[ 30.346380] FS: 0000000000000000(0000) GS:ffff95965fd40000(0000) knlGS:0000000000000000
[ 30.346385] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 30.346386] CR2: 0000000000000000 CR3: 000000000820a000 CR4: 00000000000006e0
[ 30.346387] Call Trace:
[ 30.346392] rcu_read_delay+0xab/0xf0
[ 30.346395] rcu_torture_reader+0x175/0x2e0
[ 30.346398] ? rcu_torture_reader+0x2e0/0x2e0
[ 30.346400] ? kthread+0xf0/0x130
[ 30.346402] kthread+0xf0/0x130
[ 30.346404] ? rcu_torture_timer_cb+0x10/0x10
[ 30.346406] ? kthread_destroy_worker+0x40/0x40
[ 30.346409] ret_from_fork+0x1f/0x30
[ 30.346410] Code: 03 10 5a 0f ae e8 0f 31 48 c1 e2 20 48 89 d6 48 09 c6 0f ae e8 0f 31 48 c1 e2 20 48 09 d0 48 89 c1 48 29 f1 48 39 cf 76 19 f3 90 <65> 8b 0d f9 02 10 5a 41 39 c8 74 db 48 29 c6 41 89 c8 48 01 f7
[ 30.347331] Sending NMI from CPU 0 to CPUs 7:
[ 30.347360] NMI backtrace for cpu 7
[ 30.347389] CPU: 7 PID: 773 Comm: rcu_torture_rea Not tainted 4.15.0-rc1+ #1
[ 30.347391] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
[ 30.347393] task: ffff95965e34a640 task.stack: ffffa09d8150c000
[ 30.347403] RIP: 0010:delay_tsc+0x30/0x50
[ 30.347405] RSP: 0000:ffffa09d8150fe50 EFLAGS: 00000216
[ 30.347407] RAX: 00000010ee8b5168 RBX: 0000000000000022 RCX: 0000000000074d6c
[ 30.347408] RDX: 0000001000000000 RSI: 00000010ee8403fc RDI: 00000000001e7101
[ 30.347409] RBP: ffffa09d8150fe90 R08: 0000000000000007 R09: 0000000000000001
[ 30.347410] R10: 0000000000000000 R11: 0000000000000010 R12: 0000000001d2ea95
[ 30.347412] R13: ffffffffffffff27 R14: 000000071fe45867 R15: ffffffffffffff27
[ 30.347414] FS: 0000000000000000(0000) GS:ffff95965fdc0000(0000) knlGS:0000000000000000
[ 30.347419] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 30.347421] CR2: 0000000000000000 CR3: 000000000820a000 CR4: 00000000000006e0
[ 30.347422] Call Trace:
[ 30.347432] rcu_read_delay+0xab/0xf0
[ 30.347436] rcu_torture_reader+0x175/0x2e0
[ 30.347440] ? rcu_torture_reader+0x2e0/0x2e0
[ 30.347444] ? kthread+0xf0/0x130
[ 30.347445] kthread+0xf0/0x130
[ 30.347448] ? rcu_torture_timer_cb+0x10/0x10
[ 30.347451] ? kthread_destroy_worker+0x40/0x40
[ 30.347456] ret_from_fork+0x1f/0x30
[ 30.347459] Code: 03 10 5a 0f ae e8 0f 31 48 c1 e2 20 48 89 d6 48 09 c6 0f ae e8 0f 31 48 c1 e2 20 48 09 d0 48 89 c1 48 29 f1 48 39 cf 76 19 f3 90 <65> 8b 0d f9 02 10 5a 41 39 c8 74 db 48 29 c6 41 89 c8 48 01 f7
[ 30.348367] rcu_sched kthread starved for 21002 jiffies! g18446744073709551404 c18446744073709551403 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x402 ->cpu=7
[ 30.348370] rcu_sched I15008 8 2 0x80080000
[ 30.348398] Call Trace:
[ 30.348405] ? __schedule+0x316/0x6b0
[ 30.348410] schedule+0x2d/0x80
[ 30.348414] schedule_timeout+0x159/0x3f0
[ 30.348422] ? __next_timer_interrupt+0xc0/0xc0
[ 30.348428] rcu_gp_kthread+0x627/0xd90
[ 30.348436] ? migrate_swap_stop+0x161/0x180
[ 30.348439] kthread+0xf0/0x130
[ 30.348444] ? rcu_barrier_sched+0x10/0x10
[ 30.348446] ? kthread_destroy_worker+0x40/0x40
[ 30.348448] ret_from_fork+0x1f/0x30
[ 30.371242] schedule_timeout: Waylayed timer base->clk: 0xfffb884b jiffies: 0xfffbe2c3 base->next_expiry: 0xfffb884a timer->flags: 0x20c00007 timer->expires 0xfffb9093 idx: 83 idx_now: f2 base->pending_map 1000 0 1020000000008 800000000000 0 2 0 0 0
[ 30.600337] clocksource: timekeeping watchdog on CPU1: Marking clocksource 'tsc' as unstable because the skew is too large:

And the qemu command is as follows:

qemu-system-x86_64 -enable-kvm -nographic -smp 8 -serial file:/home/paulmck/public_git/linux-rcu/tools/testing/selftests/rcutorture/res/2017.11.28-11:58:02/TREE04/console.log -m 512 -kernel /home/paulmck/public_git/linux-rcu/tools/testing/selftests/rcutorture/res/2017.11.28-11:58:02/TREE04/bzImage -append "noapic selinux=0 initcall_debug debug console=ttyS0 rcutorture.torture_type=rcu_bh rcutree.rcu_fanout_leaf=4 rcutorture.n_barrier_cbs=4 rcutorture.stat_interval=15 rcutorture.shutdown_secs=1800 rcutorture.test_no_idle_hz=1 rcutorture.verbose=1"

You will of course want to adjust the -serial and -kernel parameters.

------------------------------------------------------------------------
TREE04.2
------------------------------------------------------------------------

[ 27.630095] INFO: rcu_bh detected stalls on CPUs/tasks:
[ 27.632352] 1-...!: (20 GPs behind) idle=fc6/1/4611686018427387904 softirq=0/0 fqs=2 last_accelerate: 0000/d80e, nonlazy_posted: 0, LD
[ 27.634299] 3-...!: (121 GPs behind) idle=c32/1/4611686018427387904 softirq=0/0 fqs=2 last_accelerate: 0000/d80e, nonlazy_posted: 0, LD
[ 27.636244] 4-...!: (121 GPs behind) idle=c92/1/4611686018427387904 softirq=0/0 fqs=2 last_accelerate: 0000/d80e, nonlazy_posted: 0, LD
[ 27.638271] 6-...!: (54 GPs behind) idle=93e/1/4611686018427387904 softirq=0/0 fqs=2 last_accelerate: 0000/d80e, nonlazy_posted: 0, LD
[ 27.640210] (detected by 0, t=21002 jiffies, g=-179, c=-180, q=0)
[ 27.641179] Sending NMI from CPU 0 to CPUs 1:
[ 27.641926] NMI backtrace for cpu 1
[ 27.641946] CPU: 1 PID: 769 Comm: rcu_torture_rea Not tainted 4.15.0-rc1+ #1
[ 27.641947] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
[ 27.641949] task: ffff96c7dde2b300 task.stack: ffffaa3180d7c000
[ 27.641961] RIP: 0010:delay_tsc+0x30/0x50
[ 27.641962] RSP: 0000:ffffaa3180d7fe50 EFLAGS: 00000216
[ 27.641963] RAX: 0000000f94f40c86 RBX: ffffffffb3979a90 RCX: 000000000004bc7e
[ 27.641964] RDX: 0000000f00000000 RSI: 0000000f94ef5008 RDI: 000000000006171a
[ 27.641965] RBP: ffffaa3180d7fe90 R08: 0000000000000001 R09: ffff96c7dfc5a040
[ 27.641966] R10: 0000000000000000 R11: ffffaa3180d7fe58 R12: ffffffffffffff4c
[ 27.641967] R13: 0000000000000000 R14: 000000067f2f5cf8 R15: ffffffffffffff4d
[ 27.641968] FS: 0000000000000000(0000) GS:ffff96c7dfc40000(0000) knlGS:0000000000000000
[ 27.641973] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 27.641974] CR2: ffffaa31802f0000 CR3: 000000001780a000 CR4: 00000000000006e0
[ 27.641975] Call Trace:
[ 27.641995] rcu_read_delay+0xe8/0xf0
[ 27.641999] rcu_torture_reader+0x175/0x2e0
[ 27.642001] ? rcu_torture_reader+0x2e0/0x2e0
[ 27.642005] ? kthread+0xf0/0x130
[ 27.642007] kthread+0xf0/0x130
[ 27.642009] ? rcu_torture_timer_cb+0x10/0x10
[ 27.642010] ? kthread_destroy_worker+0x40/0x40
[ 27.642016] ? call_usermodehelper_exec_async+0x11c/0x120
[ 27.642023] ret_from_fork+0x1f/0x30
[ 27.642025] Code: 03 30 4e 0f ae e8 0f 31 48 c1 e2 20 48 89 d6 48 09 c6 0f ae e8 0f 31 48 c1 e2 20 48 09 d0 48 89 c1 48 29 f1 48 39 cf 76 19 f3 90 <65> 8b 0d f9 02 30 4e 41 39 c8 74 db 48 29 c6 41 89 c8 48 01 f7
[ 27.642920] Sending NMI from CPU 0 to CPUs 3:
[ 27.642939] NMI backtrace for cpu 3
[ 27.642956] CPU: 3 PID: 775 Comm: rcu_torture_rea Not tainted 4.15.0-rc1+ #1
[ 27.642956] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
[ 27.642958] task: ffff96c7dde20000 task.stack: ffffaa3180d94000
[ 27.642962] RIP: 0010:delay_tsc+0x30/0x50
[ 27.642962] RSP: 0018:ffffaa3180d97e50 EFLAGS: 00000216
[ 27.642964] RAX: 0000000f9513283c RBX: 000000000000000e RCX: 00000000001c6e1e
[ 27.642965] RDX: 0000000f00000000 RSI: 0000000f94f6ba1e RDI: 00000000001e8454
[ 27.642966] RBP: ffffaa3180d97e90 R08: 0000000000000003 R09: 0000000000000001
[ 27.642967] R10: 0000000000000000 R11: 0000000000000282 R12: 0000000001a93a71
[ 27.642968] R13: ffffffffffffff4c R14: 000000067d0c49dd R15: ffffffffffffff4d
[ 27.642969] FS: 0000000000000000(0000) GS:ffff96c7dfcc0000(0000) knlGS:0000000000000000
[ 27.642973] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 27.642974] CR2: 0000000008382b40 CR3: 000000001df34000 CR4: 00000000000006e0
[ 27.642974] Call Trace:
[ 27.642978] rcu_read_delay+0xab/0xf0
[ 27.642980] rcu_torture_reader+0x175/0x2e0
[ 27.642982] ? rcu_torture_reader+0x2e0/0x2e0
[ 27.642984] ? kthread+0xf0/0x130
[ 27.642985] kthread+0xf0/0x130
[ 27.642987] ? rcu_torture_timer_cb+0x10/0x10
[ 27.642988] ? kthread_destroy_worker+0x40/0x40
[ 27.642991] ? call_usermodehelper_exec_async+0x11c/0x120
[ 27.642993] ret_from_fork+0x1f/0x30
[ 27.642994] Code: 03 30 4e 0f ae e8 0f 31 48 c1 e2 20 48 89 d6 48 09 c6 0f ae e8 0f 31 48 c1 e2 20 48 09 d0 48 89 c1 48 29 f1 48 39 cf 76 19 f3 90 <65> 8b 0d f9 02 30 4e 41 39 c8 74 db 48 29 c6 41 89 c8 48 01 f7
[ 27.643940] Sending NMI from CPU 0 to CPUs 4:
[ 27.643962] NMI backtrace for cpu 4
[ 27.643983] CPU: 4 PID: 770 Comm: rcu_torture_rea Not tainted 4.15.0-rc1+ #1
[ 27.643984] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
[ 27.643986] task: ffff96c7dde2bfc0 task.stack: ffffaa318151c000
[ 27.643994] RIP: 0010:rcu_read_delay+0x46/0xf0
[ 27.643995] RSP: 0018:ffffaa318151fe58 EFLAGS: 00000206
[ 27.643997] RAX: 000000000014888f RBX: ffffffffb3979a90 RCX: 0000000000000af0
[ 27.643998] RDX: 00000000000006fb RSI: 0000000000000001 RDI: ffffaa318151fe90
[ 27.643999] RBP: ffffaa318151fe90 R08: 0000000000000004 R09: ffff96c7dfd1a040
[ 27.644000] R10: 0000000000000000 R11: ffffaa318151fe58 R12: ffffffffffffff4c
[ 27.644001] R13: 0000000000000000 R14: 000000067f50d977 R15: ffffffffffffff4d
[ 27.644003] FS: 0000000000000000(0000) GS:ffff96c7dfd00000(0000) knlGS:0000000000000000
[ 27.644007] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 27.644008] CR2: 00000000f7dbdf80 CR3: 000000001780a000 CR4: 00000000000006e0
[ 27.644009] Call Trace:
[ 27.644015] rcu_torture_reader+0x175/0x2e0
[ 27.644018] ? rcu_torture_reader+0x2e0/0x2e0
[ 27.644021] ? kthread+0xf0/0x130
[ 27.644022] kthread+0xf0/0x130
[ 27.644024] ? rcu_torture_timer_cb+0x10/0x10
[ 27.644025] ? kthread_destroy_worker+0x40/0x40
[ 27.644031] ret_from_fork+0x1f/0x30
[ 27.644032] Code: 86 01 00 48 f7 f1 48 85 d2 74 4c 48 89 ef e8 b2 14 08 00 48 63 15 df 5f 4d 02 48 8d 14 92 48 8d 0c 92 31 d2 48 c1 e1 04 48 f7 f1 <48> 85 d2 0f 84 8f 00 00 00 65 8b 05 ba 77 b6 4e a9 ff ff ff 7f
[ 27.644955] Sending NMI from CPU 0 to CPUs 6:
[ 27.644973] NMI backtrace for cpu 6
[ 27.644990] CPU: 6 PID: 773 Comm: rcu_torture_rea Not tainted 4.15.0-rc1+ #1
[ 27.644990] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
[ 27.644992] task: ffff96c7debc2640 task.stack: ffffaa318152c000
[ 27.644995] RIP: 0010:delay_tsc+0x1c/0x50
[ 27.644996] RSP: 0000:ffffaa318152fe50 EFLAGS: 00000246
[ 27.644998] RAX: 0000000095510f68 RBX: ffffffffb3979a90 RCX: 0000000000000006
[ 27.644999] RDX: 000000000000000f RSI: 0000000f954b5738 RDI: 0000000000061754
[ 27.644999] RBP: ffffaa318152fe90 R08: 0000000000000006 R09: 0000000000000001
[ 27.645000] R10: 0000000000000000 R11: ffffaa318152fe58 R12: ffffffffffffff4c
[ 27.645001] R13: 0000000000000000 R14: 000000067f5d7e21 R15: ffffffffffffff4d
[ 27.645003] FS: 0000000000000000(0000) GS:ffff96c7dfd80000(0000) knlGS:0000000000000000
[ 27.645006] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 27.645007] CR2: 0000000000000000 CR3: 000000001780a000 CR4: 00000000000006e0
[ 27.645007] Call Trace:
[ 27.645010] rcu_read_delay+0xe8/0xf0
[ 27.645012] rcu_torture_reader+0x175/0x2e0
[ 27.645014] ? rcu_torture_reader+0x2e0/0x2e0
[ 27.645016] ? kthread+0xf0/0x130
[ 27.645017] kthread+0xf0/0x130
[ 27.645019] ? rcu_torture_timer_cb+0x10/0x10
[ 27.645020] ? kthread_destroy_worker+0x40/0x40
[ 27.645022] ret_from_fork+0x1f/0x30
[ 27.645023] Code: 00 f7 e2 48 8d 7a 01 ff 25 e2 80 5f 00 66 90 65 44 8b 05 28 03 30 4e 0f ae e8 0f 31 48 c1 e2 20 48 89 d6 48 09 c6 0f ae e8 0f 31 <48> c1 e2 20 48 09 d0 48 89 c1 48 29 f1 48 39 cf 76 19 f3 90 65
[ 27.645975] rcu_bh kthread starved for 20835 jiffies! g18446744073709551437 c18446744073709551436 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x402 ->cpu=2
[ 27.645988] rcu_bh I15008 9 2 0x80080000
[ 27.646000] Call Trace:
[ 27.646011] ? __schedule+0x316/0x6b0
[ 27.646013] schedule+0x2d/0x80
[ 27.646017] schedule_timeout+0x159/0x3f0
[ 27.646025] ? __next_timer_interrupt+0xc0/0xc0
[ 27.646029] rcu_gp_kthread+0x627/0xd90
[ 27.646036] ? migrate_swap_stop+0x160/0x180
[ 27.646039] kthread+0xf0/0x130
[ 27.646041] ? rcu_barrier_sched+0x10/0x10
[ 27.646043] ? kthread_destroy_worker+0x40/0x40
[ 27.646048] ret_from_fork+0x1f/0x30
[ 27.646111] schedule_timeout: Waylayed timer base->clk: 0xfffb86af jiffies: 0xfffbd81e base->next_expiry: 0xfffb86af timer->flags: 0xbc00002 timer->expires 0xfffb86ae idx: 2f idx_now: ed base->pending_map 800000000000 100000000 10000000000 0 200040 2 0 0 0
[ 33.898125] INFO: rcu_sched detected stalls on CPUs/tasks:
[ 33.899348] 1-...!: (47 GPs behind) idle=01a/1/4611686018427387904 softirq=0/0 fqs=0 last_accelerate: 0000/f08a, nonlazy_posted: 0, LD
[ 33.901444] 2-...!: (15 GPs behind) idle=b3a/1/4611686018427387904 softirq=0/0 fqs=0 last_accelerate: 0000/f08a, nonlazy_posted: 0, LD
[ 33.903620] 4-...!: (42 GPs behind) idle=ce6/1/4611686018427387904 softirq=0/0 fqs=0 last_accelerate: 0000/f08a, nonlazy_posted: 0, LD
[ 33.905677] 5-...!: (0 ticks this GP) idle=bbe/1/4611686018427387904 softirq=0/0 fqs=0 last_accelerate: 0000/f08a, nonlazy_posted: 0, LD
[ 33.907820] 6-...!: (24 ticks this GP) idle=992/1/4611686018427387904 softirq=1/1 fqs=0 last_accelerate: 0000/f08a, nonlazy_posted: 0, LD
[ 33.909911] 7-...!: (36 ticks this GP) idle=176/1/4611686018427387904 softirq=2/2 fqs=0 last_accelerate: 0000/f08a, nonlazy_posted: 0, LD
[ 33.912077] (detected by 0, t=21002 jiffies, g=-213, c=-214, q=34)
[ 33.913168] Sending NMI from CPU 0 to CPUs 1:
[ 33.913923] NMI backtrace for cpu 1
[ 33.913944] CPU: 1 PID: 769 Comm: rcu_torture_rea Not tainted 4.15.0-rc1+ #1
[ 33.913945] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
[ 33.913947] task: ffff96c7dde2b300 task.stack: ffffaa3180d7c000
[ 33.913954] RIP: 0010:__local_bh_enable_ip+0x28/0x50
[ 33.913955] RSP: 0000:ffffaa3180d7fe78 EFLAGS: 00000246
[ 33.913957] RAX: 0000000000000000 RBX: ffffffffb3979a90 RCX: 000000000000000a
[ 33.913958] RDX: ffffffffb22462c0 RSI: 00000000fffffe01 RDI: ffffffffb14a58e0
[ 33.913958] RBP: ffffaa3180d7ff00 R08: 0000000000000001 R09: 0000000000000001
[ 33.913959] R10: 0000000000000000 R11: ffffaa3180d7fe00 R12: ffffffffffffff62
[ 33.913960] R13: 0000000000000000 R14: 00000007f508d9b1 R15: ffffffffffffff62
[ 33.913961] FS: 0000000000000000(0000) GS:ffff96c7dfc40000(0000) knlGS:0000000000000000
[ 33.913966] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 33.913967] CR2: ffffaa31802f0000 CR3: 000000001780a000 CR4: 00000000000006e0
[ 33.913968] Call Trace:
[ 33.913977] rcu_torture_reader+0xe3/0x2e0
[ 33.913980] ? rcu_torture_reader+0x2e0/0x2e0
[ 33.913984] ? kthread+0xf0/0x130
[ 33.913985] kthread+0xf0/0x130
[ 33.913987] ? rcu_torture_timer_cb+0x10/0x10
[ 33.913988] ? kthread_destroy_worker+0x40/0x40
[ 33.913992] ? call_usermodehelper_exec_async+0x11c/0x120
[ 33.913998] ret_from_fork+0x1f/0x30
[ 33.914000] Code: c3 66 90 83 ee 01 65 8b 05 36 3b bb 4e f7 de a9 00 00 0f 00 75 1d 65 01 35 26 3b bb 4e 65 8b 05 1f 3b bb 4e a9 00 ff 1f 00 74 0c <65> ff 0d 11 3b bb 4e c3 0f ff eb df 65 8b 05 75 ee bb 4e 85 c0
[ 33.914918] Sending NMI from CPU 0 to CPUs 2:
[ 33.914936] NMI backtrace for cpu 2
[ 33.914953] CPU: 2 PID: 771 Comm: rcu_torture_rea Not tainted 4.15.0-rc1+ #1
[ 33.914954] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
[ 33.914955] task: ffff96c7de184c80 task.stack: ffffaa318149c000
[ 33.914962] RIP: 0010:__local_bh_enable_ip+0x28/0x50
[ 33.914963] RSP: 0000:ffffaa318149fe78 EFLAGS: 00000246
[ 33.914964] RAX: 0000000000000000 RBX: ffffffffb3979a90 RCX: 000000000000000a
[ 33.914965] RDX: ffffffffb22462c0 RSI: 00000000fffffe01 RDI: ffffffffb14a58e0
[ 33.914966] RBP: ffffaa318149ff00 R08: 0000000000000002 R09: 0000000000000001
[ 33.914967] R10: 0000000000000000 R11: 0000000000000000 R12: ffffffffffffff62
[ 33.914968] R13: 0000000000000000 R14: 00000007f5186150 R15: ffffffffffffff62
[ 33.914970] FS: 0000000000000000(0000) GS:ffff96c7dfc80000(0000) knlGS:0000000000000000
[ 33.914974] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 33.914975] CR2: 0000000000000000 CR3: 000000001780a000 CR4: 00000000000006e0
[ 33.914976] Call Trace:
[ 33.914985] rcu_torture_reader+0xe3/0x2e0
[ 33.914988] ? rcu_torture_reader+0x2e0/0x2e0
[ 33.914992] ? kthread+0xf0/0x130
[ 33.914993] kthread+0xf0/0x130
[ 33.914995] ? rcu_torture_timer_cb+0x10/0x10
[ 33.914996] ? kthread_destroy_worker+0x40/0x40
[ 33.915000] ? call_usermodehelper_exec_async+0x11c/0x120
[ 33.915006] ret_from_fork+0x1f/0x30
[ 33.915007] Code: c3 66 90 83 ee 01 65 8b 05 36 3b bb 4e f7 de a9 00 00 0f 00 75 1d 65 01 35 26 3b bb 4e 65 8b 05 1f 3b bb 4e a9 00 ff 1f 00 74 0c <65> ff 0d 11 3b bb 4e c3 0f ff eb df 65 8b 05 75 ee bb 4e 85 c0
[ 33.915934] Sending NMI from CPU 0 to CPUs 4:
[ 33.915956] NMI backtrace for cpu 4
[ 33.915977] CPU: 4 PID: 770 Comm: rcu_torture_rea Not tainted 4.15.0-rc1+ #1
[ 33.915978] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
[ 33.915980] task: ffff96c7dde2bfc0 task.stack: ffffaa318151c000
[ 33.915990] RIP: 0010:delay_tsc+0x30/0x50
[ 33.915990] RSP: 0018:ffffaa318151fe50 EFLAGS: 00000216
[ 33.915992] RAX: 000000127f0117e3 RBX: 0000000000000013 RCX: 00000000000556dc
[ 33.915993] RDX: 0000001200000000 RSI: 000000127efbc107 RDI: 00000000001e73d2
[ 33.915994] RBP: ffffaa318151fe90 R08: 0000000000000004 R09: ffff96c7dfd1a040
[ 33.915995] R10: 0000000000000000 R11: ffffaa318151fe58 R12: 000000000209089c
[ 33.915996] R13: ffffffffffffff62 R14: 00000007f349a167 R15: ffffffffffffff62
[ 33.915998] FS: 0000000000000000(0000) GS:ffff96c7dfd00000(0000) knlGS:0000000000000000
[ 33.916002] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 33.916003] CR2: 00000000f7dbdf80 CR3: 000000001780a000 CR4: 00000000000006e0
[ 33.916004] Call Trace:
[ 33.916012] rcu_read_delay+0xab/0xf0
[ 33.916016] rcu_torture_reader+0x175/0x2e0
[ 33.916018] ? rcu_torture_reader+0x2e0/0x2e0
[ 33.916021] ? kthread+0xf0/0x130
[ 33.916023] kthread+0xf0/0x130
[ 33.916024] ? rcu_torture_timer_cb+0x10/0x10
[ 33.916026] ? kthread_destroy_worker+0x40/0x40
[ 33.916031] ret_from_fork+0x1f/0x30
[ 33.916033] Code: 03 30 4e 0f ae e8 0f 31 48 c1 e2 20 48 89 d6 48 09 c6 0f ae e8 0f 31 48 c1 e2 20 48 09 d0 48 89 c1 48 29 f1 48 39 cf 76 19 f3 90 <65> 8b 0d f9 02 30 4e 41 39 c8 74 db 48 29 c6 41 89 c8 48 01 f7
[ 33.916949] Sending NMI from CPU 0 to CPUs 5:
[ 33.916968] NMI backtrace for cpu 5
[ 33.916985] CPU: 5 PID: 774 Comm: rcu_torture_rea Not tainted 4.15.0-rc1+ #1
[ 33.916986] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
[ 33.916987] task: ffff96c7debc0cc0 task.stack: ffffaa3181534000
[ 33.916990] RIP: 0010:rcu_read_delay+0x46/0xf0
[ 33.916991] RSP: 0018:ffffaa3181537e58 EFLAGS: 00000206
[ 33.916993] RAX: 00000000000aa73b RBX: ffffffffb3979a90 RCX: 0000000000000af0
[ 33.916994] RDX: 00000000000008aa RSI: 0000000000000001 RDI: ffffaa3181537e90
[ 33.916995] RBP: ffffaa3181537e90 R08: 0000000000000005 R09: 0000000000000001
[ 33.916995] R10: 0000000000000000 R11: 0000000000000002 R12: ffffffffffffff62
[ 33.916996] R13: 0000000000000000 R14: 00000007f5376188 R15: ffffffffffffff62
[ 33.916998] FS: 0000000000000000(0000) GS:ffff96c7dfd40000(0000) knlGS:0000000000000000
[ 33.917001] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 33.917002] CR2: 00000000f7eb3010 CR3: 000000001780a000 CR4: 00000000000006e0
[ 33.917003] Call Trace:
[ 33.917007] rcu_torture_reader+0x175/0x2e0
[ 33.917009] ? rcu_torture_reader+0x2e0/0x2e0
[ 33.917011] ? kthread+0xf0/0x130
[ 33.917012] kthread+0xf0/0x130
[ 33.917014] ? rcu_torture_timer_cb+0x10/0x10
[ 33.917015] ? kthread_destroy_worker+0x40/0x40
[ 33.917017] ret_from_fork+0x1f/0x30
[ 33.917019] Code: 86 01 00 48 f7 f1 48 85 d2 74 4c 48 89 ef e8 b2 14 08 00 48 63 15 df 5f 4d 02 48 8d 14 92 48 8d 0c 92 31 d2 48 c1 e1 04 48 f7 f1 <48> 85 d2 0f 84 8f 00 00 00 65 8b 05 ba 77 b6 4e a9 ff ff ff 7f
[ 33.917964] Sending NMI from CPU 0 to CPUs 6:
[ 33.917981] NMI backtrace for cpu 6
[ 33.917999] CPU: 6 PID: 773 Comm: rcu_torture_rea Not tainted 4.15.0-rc1+ #1
[ 33.918000] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
[ 33.918001] task: ffff96c7debc2640 task.stack: ffffaa318152c000
[ 33.918008] RIP: 0010:native_sched_clock+0x7/0x70
[ 33.918009] RSP: 0000:ffffaa318152fe70 EFLAGS: 00000282
[ 33.918010] RAX: 000000007f3eed81 RBX: ffffffffb3979a90 RCX: 000000000000000a
[ 33.918011] RDX: 0000000000000012 RSI: 00000000fffffe01 RDI: 0000000000000001
[ 33.918012] RBP: ffffaa318152ff00 R08: 0000000000000006 R09: 0000000000000101
[ 33.918013] R10: 0000000000000000 R11: ffffaa318152fe58 R12: ffffffffffffff62
[ 33.918014] R13: 0000000000000000 R14: 00000007f546e075 R15: ffffffffffffff62
[ 33.918016] FS: 0000000000000000(0000) GS:ffff96c7dfd80000(0000) knlGS:0000000000000000
[ 33.918019] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 33.918020] CR2: 0000000000000000 CR3: 000000001780a000 CR4: 00000000000006e0
[ 33.918021] Call Trace:
[ 33.918026] trace_clock_local+0x5/0x10
[ 33.918029] rcu_torture_reader+0x146/0x2e0
[ 33.918031] ? rcu_torture_reader+0x2e0/0x2e0
[ 33.918033] ? kthread+0xf0/0x130
[ 33.918034] kthread+0xf0/0x130
[ 33.918035] ? rcu_torture_timer_cb+0x10/0x10
[ 33.918037] ? kthread_destroy_worker+0x40/0x40
[ 33.918039] ret_from_fork+0x1f/0x30
[ 33.918041] Code: 89 47 04 65 8b 05 fa 67 bf 4e 39 c2 75 c6 f3 c3 0f 1f 40 00 c3 0f 1f 44 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 0f 31 <48> c1 e2 20 48 09 c2 65 8b 0d cb 67 bf 4e 83 e1 01 48 c1 e1 04
[ 33.918979] Sending NMI from CPU 0 to CPUs 7:
[ 33.918997] NMI backtrace for cpu 7
[ 33.919013] CPU: 7 PID: 772 Comm: rcu_torture_rea Not tainted 4.15.0-rc1+ #1
[ 33.919014] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
[ 33.919015] task: ffff96c7debc72c0 task.stack: ffffaa3181524000
[ 33.919021] RIP: 0010:delay_tsc+0x1c/0x50
[ 33.919022] RSP: 0018:ffffaa3181527e50 EFLAGS: 00000246
[ 33.919024] RAX: 000000007f5dd538 RBX: 0000000000000026 RCX: 0000000000000007
[ 33.919025] RDX: 0000000000000012 RSI: 000000127f4c7028 RDI: 00000000001e736b
[ 33.919026] RBP: ffffaa3181527e90 R08: 0000000000000007 R09: 0000000000000101
[ 33.919027] R10: 0000000000000000 R11: ffffaa3181527e58 R12: 0000000002095dd0
[ 33.919028] R13: ffffffffffffff62 R14: 00000007f49676e8 R15: ffffffffffffff62
[ 33.919029] FS: 0000000000000000(0000) GS:ffff96c7dfdc0000(0000) knlGS:0000000000000000
[ 33.919033] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 33.919033] CR2: 00000000f7ecbca3 CR3: 000000001780a000 CR4: 00000000000006e0
[ 33.919034] Call Trace:
[ 33.919038] rcu_read_delay+0xab/0xf0
[ 33.919040] rcu_torture_reader+0x175/0x2e0
[ 33.919042] ? rcu_torture_reader+0x2e0/0x2e0
[ 33.919044] ? kthread+0xf0/0x130
[ 33.919045] kthread+0xf0/0x130
[ 33.919046] ? rcu_torture_timer_cb+0x10/0x10
[ 33.919048] ? kthread_destroy_worker+0x40/0x40
[ 33.919050] ret_from_fork+0x1f/0x30
[ 33.919051] Code: 00 f7 e2 48 8d 7a 01 ff 25 e2 80 5f 00 66 90 65 44 8b 05 28 03 30 4e 0f ae e8 0f 31 48 c1 e2 20 48 89 d6 48 09 c6 0f ae e8 0f 31 <48> c1 e2 20 48 09 d0 48 89 c1 48 29 f1 48 39 cf 76 19 f3 90 65
[ 33.919997] rcu_sched kthread starved for 21019 jiffies! g18446744073709551403 c18446744073709551402 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x402 ->cpu=5
[ 33.919999] rcu_sched I15008 8 2 0x80080000
[ 33.920013] Call Trace:
[ 33.920020] ? __schedule+0x316/0x6b0
[ 33.920022] schedule+0x2d/0x80
[ 33.920024] schedule_timeout+0x159/0x3f0
[ 33.920035] ? __next_timer_interrupt+0xc0/0xc0
[ 33.920038] rcu_gp_kthread+0x627/0xd90
[ 33.920046] ? migrate_swap_stop+0x161/0x180
[ 33.920049] kthread+0xf0/0x130
[ 33.920051] ? rcu_barrier_sched+0x10/0x10
[ 33.920052] ? kthread_destroy_worker+0x40/0x40
[ 33.920056] ret_from_fork+0x1f/0x30
[ 33.920133] schedule_timeout: Waylayed timer base->clk: 0xfffb86c3 jiffies: 0xfffbf0a0 base->next_expiry: 0xfffb86c3 timer->flags: 0x34000005 timer->expires 0xfffb9e83 idx: d0 idx_now: f9 base->pending_map 8 0 10000000000 10000 0 2 0 0 0

And the qemu command is as follows:

qemu-system-x86_64 -enable-kvm -nographic -smp 8 -serial file:/home/paulmck/public_git/linux-rcu/tools/testing/selftests/rcutorture/res/2017.11.28-11:58:02/TREE04.2/console.log -m 512 -kernel /home/paulmck/public_git/linux-rcu/tools/testing/selftests/rcutorture/res/2017.11.28-11:58:02/TREE04/bzImage -append "noapic selinux=0 initcall_debug debug console=ttyS0 rcutorture.torture_type=rcu_bh rcutree.rcu_fanout_leaf=4 rcutorture.n_barrier_cbs=4 rcutorture.stat_interval=15 rcutorture.shutdown_secs=1800 rcutorture.test_no_idle_hz=1 rcutorture.verbose=1"