On Tue, 12 Nov 2013, Mike Galbraith wrote:
> FYI, shiny new (and virgin) 3.12.0-rt1 nohz_full config is deadlock
> prone. I was measuring fastpath cost yesterday with pinned pipe-test..
>
> x3550 M3 E5620 (bloatware config)
> CONFIG_NO_HZ_IDLE - CPU3
> 2.957012 usecs/loop -- avg 2.957012 676.4 KHz 1.000
>
> CONFIG_NO_HZ_FULL - CPU1 != nohz_full
> 3.735279 usecs/loop -- avg 3.735279 535.4 KHz .791
>
> CONFIG_NO_HZ_FULL - CPU3 == nohz_full
> 5.922986 usecs/loop -- avg 5.922986 337.7 KHz .499
>
> (ow)
>
> ..and noticed box eventually deadlocks, if it boots, which the instance
> below didn't.
> --- <RT exception stack> ---
> #11 [ffff88017b243e90] _raw_spin_lock at ffffffff815d2596
> #12 [ffff88017b243e90] rt_mutex_trylock at ffffffff815d15be
> #13 [ffff88017b243eb0] get_next_timer_interrupt at ffffffff81063b42
> #14 [ffff88017b243f00] tick_nohz_stop_sched_tick at ffffffff810bd1fd
> #15 [ffff88017b243f70] tick_nohz_irq_exit at ffffffff810bd7d2
> #16 [ffff88017b243f90] irq_exit at ffffffff8105b02d
> #17 [ffff88017b243fb0] reschedule_interrupt at ffffffff815db3dd
> --- <IRQ stack> ---
> #18 [ffff88017a2a9bc8] reschedule_interrupt at ffffffff815db3dd
> [exception RIP: task_blocks_on_rt_mutex+51]
> RIP: ffffffff810c1ed3 RSP: ffff88017a2a9c78 RFLAGS: 00000296
> RAX: 0000000000080000 RBX: 0000000000000001 RCX: 0000000000000000
> RDX: ffff88017a27d5a0 RSI: ffff88017a2a9d00 RDI: ffff880179ef8000
> RBP: ffff880179ef8000 R8: ffff880179cfef50 R9: ffff880179ef8018
> R10: ffff880179cfef51 R11: 0000000000000002 R12: 0000000000000001
> R13: 0000000000000001 R14: 0000000100000000 R15: 0000000100000000
> ORIG_RAX: ffffffffffffff02 CS: 0010 SS: 0018
> #19 [ffff88017a2a9ce0] rt_spin_lock_slowlock at ffffffff815d183c
Grr....
raw_spin_lock(&lock->wait_lock);
Ditto in rt_mutex_slowtrylock()
Thanks,
tglx
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