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Date: Sat, 25 Jan 2014 06:12:40 +0100
From: Mike Galbraith <bitbucket@...ine.de>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: paulmck@...ux.vnet.ibm.com, linux-rt-users@...r.kernel.org,
Steven Rostedt <rostedt@...dmis.org>,
linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] rcu: Eliminate softirq processing from rcutree
On Fri, 2014-01-24 at 20:50 +0100, Sebastian Andrzej Siewior wrote:
> * Mike Galbraith | 2014-01-18 04:25:14 [+0100]:
>
> >> ># timers-do-not-raise-softirq-unconditionally.patch
> >> ># rtmutex-use-a-trylock-for-waiter-lock-in-trylock.patch
> >> >
> >> >..those two out does seem to have stabilized the thing.
> >>
> >> timers-do-not-raise-softirq-unconditionally.patch is on its way out.
> >>
> >> rtmutex-use-a-trylock-for-waiter-lock-in-trylock.patch confues me.
> >> Didn't you report once that your box deadlocks without this patch? Now
> >> your 64way box on the other hand does not work with it?
> >
> >If 'do not raise' is applied, 'use a trylock' won't save you. If 'do
> is this just an observation or you do know why it won't save me?
It's an observation from beyond the grave from the 64 core box that it
repeatedly did NOT save :) Autopsy photos below.
I've built 3.12.8-rt9 with Stevens v2 "timer: Raise softirq if there's
irq_work" to see if it'll survive.
nohz_full_all:
PID: 508 TASK: ffff8802739ba340 CPU: 16 COMMAND: "ksoftirqd/16"
#0 [ffff880276806a40] machine_kexec at ffffffff8103bc07
#1 [ffff880276806aa0] crash_kexec at ffffffff810d56b3
#2 [ffff880276806b70] panic at ffffffff815bf8b0
#3 [ffff880276806bf0] watchdog_overflow_callback at ffffffff810fed3d
#4 [ffff880276806c10] __perf_event_overflow at ffffffff81131928
#5 [ffff880276806ca0] perf_event_overflow at ffffffff81132254
#6 [ffff880276806cb0] intel_pmu_handle_irq at ffffffff8102078f
#7 [ffff880276806de0] perf_event_nmi_handler at ffffffff815c5825
#8 [ffff880276806e10] nmi_handle at ffffffff815c4ed3
#9 [ffff880276806ea0] default_do_nmi at ffffffff815c5063
#10 [ffff880276806ed0] do_nmi at ffffffff815c5388
#11 [ffff880276806ef0] end_repeat_nmi at ffffffff815c4371
[exception RIP: _raw_spin_trylock+48]
RIP: ffffffff815c3790 RSP: ffff880276803e28 RFLAGS: 00000002
RAX: 0000000000000010 RBX: 0000000000000010 RCX: 0000000000000002
RDX: ffff880276803e28 RSI: 0000000000000018 RDI: 0000000000000001
RBP: ffffffff815c3790 R8: ffffffff815c3790 R9: 0000000000000018
R10: ffff880276803e28 R11: 0000000000000002 R12: ffffffffffffffff
R13: ffff880273a0c000 R14: ffff8802739ba340 R15: ffff880273a03fd8
ORIG_RAX: ffff880273a03fd8 CS: 0010 SS: 0018
--- <RT exception stack> ---
#12 [ffff880276803e28] _raw_spin_trylock at ffffffff815c3790
#13 [ffff880276803e30] rt_spin_lock_slowunlock_hirq at ffffffff815c2cc8
#14 [ffff880276803e50] rt_spin_unlock_after_trylock_in_irq at ffffffff815c3425
#15 [ffff880276803e60] get_next_timer_interrupt at ffffffff810684a7
#16 [ffff880276803ed0] tick_nohz_stop_sched_tick at ffffffff810c5f2e
#17 [ffff880276803f50] tick_nohz_irq_exit at ffffffff810c6333
#18 [ffff880276803f70] irq_exit at ffffffff81060065
#19 [ffff880276803f90] smp_apic_timer_interrupt at ffffffff810358f5
#20 [ffff880276803fb0] apic_timer_interrupt at ffffffff815cbf9d
--- <IRQ stack> ---
#21 [ffff880273a03b28] apic_timer_interrupt at ffffffff815cbf9d
[exception RIP: _raw_spin_lock+50]
RIP: ffffffff815c3642 RSP: ffff880273a03bd8 RFLAGS: 00000202
RAX: 0000000000008b49 RBX: ffff880272157290 RCX: ffff8802739ba340
RDX: 0000000000008b4a RSI: 0000000000000010 RDI: ffff880273a0c000
RBP: ffff880273a03bd8 R8: 0000000000000001 R9: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: ffffffff810927b5
R13: ffff880273a03b68 R14: 0000000000000010 R15: 0000000000000010
ORIG_RAX: ffffffffffffff10 CS: 0010 SS: 0018
#22 [ffff880273a03be0] rt_spin_lock_slowlock at ffffffff815c2591
#23 [ffff880273a03cc0] rt_spin_lock at ffffffff815c3362
#24 [ffff880273a03cd0] run_timer_softirq at ffffffff81069002
#25 [ffff880273a03d70] handle_softirq at ffffffff81060d0f
#26 [ffff880273a03db0] do_current_softirqs at ffffffff81060f3c
#27 [ffff880273a03e20] run_ksoftirqd at ffffffff81061045
#28 [ffff880273a03e40] smpboot_thread_fn at ffffffff81089c31
#29 [ffff880273a03ec0] kthread at ffffffff810807fe
#30 [ffff880273a03f50] ret_from_fork at ffffffff815cb28c
nohz_tick:
PID: 6948 TASK: ffff880272d1f1c0 CPU: 29 COMMAND: "tbench"
#0 [ffff8802769a6a40] machine_kexec at ffffffff8103bc07
#1 [ffff8802769a6aa0] crash_kexec at ffffffff810d3e93
#2 [ffff8802769a6b70] panic at ffffffff815bce70
#3 [ffff8802769a6bf0] watchdog_overflow_callback at ffffffff810fd51d
#4 [ffff8802769a6c10] __perf_event_overflow at ffffffff8112f1f8
#5 [ffff8802769a6ca0] perf_event_overflow at ffffffff8112fb14
#6 [ffff8802769a6cb0] intel_pmu_handle_irq at ffffffff8102078f
#7 [ffff8802769a6de0] perf_event_nmi_handler at ffffffff815c2de5
#8 [ffff8802769a6e10] nmi_handle at ffffffff815c2493
#9 [ffff8802769a6ea0] default_do_nmi at ffffffff815c2623
#10 [ffff8802769a6ed0] do_nmi at ffffffff815c2948
#11 [ffff8802769a6ef0] end_repeat_nmi at ffffffff815c1931
[exception RIP: preempt_schedule+36]
RIP: ffffffff815be944 RSP: ffff8802769a3d98 RFLAGS: 00000002
RAX: 0000000000000010 RBX: 0000000000000010 RCX: 0000000000000002
RDX: ffff8802769a3d98 RSI: 0000000000000018 RDI: 0000000000000001
RBP: ffffffff815be944 R8: ffffffff815be944 R9: 0000000000000018
R10: ffff8802769a3d98 R11: 0000000000000002 R12: ffffffffffffffff
R13: ffff880273f74000 R14: ffff880272d1f1c0 R15: ffff880269cedfd8
ORIG_RAX: ffff880269cedfd8 CS: 0010 SS: 0018
--- <RT exception stack> ---
#12 [ffff8802769a3d98] preempt_schedule at ffffffff815be944
#13 [ffff8802769a3db0] _raw_spin_trylock at ffffffff815c0d6e
#14 [ffff8802769a3dc0] rt_spin_lock_slowunlock_hirq at ffffffff815c0288
#15 [ffff8802769a3de0] rt_spin_unlock_after_trylock_in_irq at ffffffff815c09e5
#16 [ffff8802769a3df0] run_local_timers at ffffffff81068025
#17 [ffff8802769a3e10] update_process_times at ffffffff810680ac
#18 [ffff8802769a3e40] tick_sched_handle at ffffffff810c3a92
#19 [ffff8802769a3e60] tick_sched_timer at ffffffff810c3d2f
#20 [ffff8802769a3e90] __run_hrtimer at ffffffff8108471d
#21 [ffff8802769a3ed0] hrtimer_interrupt at ffffffff8108497a
#22 [ffff8802769a3f70] local_apic_timer_interrupt at ffffffff810349e6
#23 [ffff8802769a3f90] smp_apic_timer_interrupt at ffffffff810358ee
#24 [ffff8802769a3fb0] apic_timer_interrupt at ffffffff815c955d
--- <IRQ stack> ---
#25 [ffff880269ced848] apic_timer_interrupt at ffffffff815c955d
[exception RIP: _raw_spin_lock+53]
RIP: ffffffff815c0c05 RSP: ffff880269ced8f8 RFLAGS: 00000202
RAX: 0000000000000b7b RBX: 0000000000000282 RCX: ffff880272d1f1c0
RDX: 0000000000000b7d RSI: ffff880269ceda38 RDI: ffff880273f74000
RBP: ffff880269ced8f8 R8: 0000000000000001 R9: 00000000b54d13a4
R10: 0000000000000001 R11: 0000000000000001 R12: ffff880269ced910
R13: ffff880276d32170 R14: ffffffff810c9030 R15: ffff880269ced8b8
ORIG_RAX: ffffffffffffff10 CS: 0010 SS: 0018
#26 [ffff880269ced900] rt_spin_lock_slowlock at ffffffff815bfb51
#27 [ffff880269ced9e0] rt_spin_lock at ffffffff815c0922
#28 [ffff880269ced9f0] lock_timer_base at ffffffff81067f92
#29 [ffff880269ceda20] mod_timer at ffffffff81069bcb
#30 [ffff880269ceda70] sk_reset_timer at ffffffff814d1e57
#31 [ffff880269ceda90] inet_csk_reset_xmit_timer at ffffffff8152d4a8
#32 [ffff880269cedac0] tcp_rearm_rto at ffffffff8152d583
#33 [ffff880269cedae0] tcp_ack at ffffffff81534085
#34 [ffff880269cedb60] tcp_rcv_established at ffffffff8153443d
#35 [ffff880269cedbb0] tcp_v4_do_rcv at ffffffff8153f56a
#36 [ffff880269cedbe0] __release_sock at ffffffff814d3891
#37 [ffff880269cedc10] release_sock at ffffffff814d3942
#38 [ffff880269cedc30] tcp_sendmsg at ffffffff8152b955
#39 [ffff880269cedd00] inet_sendmsg at ffffffff8155350e
#40 [ffff880269cedd30] sock_sendmsg at ffffffff814cea87
#41 [ffff880269cede40] sys_sendto at ffffffff814cebdf
#42 [ffff880269cedf80] tracesys at ffffffff815c8b09 (via system_call)
RIP: 00007f0441a1fc35 RSP: 00007fffdea86130 RFLAGS: 00000246
RAX: ffffffffffffffda RBX: ffffffff815c8b09 RCX: ffffffffffffffff
RDX: 000000000000248d RSI: 0000000000607260 RDI: 0000000000000004
RBP: 000000000000248d R8: 0000000000000000 R9: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fffdea86a10
R13: 00007fffdea86414 R14: 0000000000000004 R15: 0000000000607260
ORIG_RAX: 000000000000002c CS: 0033 SS: 002b
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