Messages in this thread | | | Date | Tue, 26 Apr 2022 16:22:05 -0500 | Subject | Re: [PATCH v5] locking/rwsem: Make handoff bit handling more consistent | From | john.p.donnelly@oracle ... |
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On 4/26/22 3:21 PM, Waiman Long wrote: > On 4/20/22 09:55, john.p.donnelly@oracle.com wrote: >> On 4/12/22 11:28 AM, john.p.donnelly@oracle.com wrote: >>> On 4/11/22 4:07 PM, Waiman Long wrote: >>>> >>>> On 4/11/22 17:03, john.p.donnelly@oracle.com wrote: >>>>> >>>>>>> >>>>>>> I have reached out to Waiman and he suggested this for our next >>>>>>> test pass: >>>>>>> >>>>>>> >>>>>>> 1ee326196c6658 locking/rwsem: Always try to wake waiters in >>>>>>> out_nolock path >>>>>> >>>>>> Does this commit help to avoid the lockup problem? >>>>>> >>>>>> Commit 1ee326196c6658 fixes a potential missed wakeup problem when >>>>>> a reader first in the wait queue is interrupted out without >>>>>> acquiring the lock. It is actually not a fix for commit >>>>>> d257cc8cb8d5. However, this commit changes the out_nolock path >>>>>> behavior of writers by leaving the handoff bit set when the wait >>>>>> queue isn't empty. That likely makes the missed wakeup problem >>>>>> easier to reproduce. >>>>>> >>>>>> Cheers, >>>>>> Longman >>>>>> >>>>> >>>>> Hi, >>>>> >>>>> >>>>> We are testing now >>>>> >>>>> ETA for fio soak test completion is ~15hr from now. >>>>> >>>>> I wanted to share the stack traces for future reference + occurrences. >>>>> >>>> I am looking forward to your testing results tomorrow. >>>> >>>> Cheers, >>>> Longman >>>> >>> Hi >>> >>> Our 24hr fio soak test with : >>> >>> 1ee326196c6658 locking/rwsem: Always try to wake waiters in >>> out_nolock path >>> >>> >>> applied to 5.15.30 passed. >>> >>> I suggest you append 1ee326196c6658 with : >>> >>> >>> cc: stable >>> >>> Fixes: d257cc8cb8d5 ("locking/rwsem: Make handoff bit handling >>> more consistent") >>> >>> >>> I'll leave the implementation details up to the core maintainers how >>> to do that ;-) >>> >>> ... >>> >>> Thank you >>> >>> John. >> >> Hi , >> >> >> We have observed another panic with : >> >> 1ee326196c6658 locking/rwsem: Always try to wake waiters in out_nolock >> path >> >> Applied to 5.15.30 : >> >> > Sorry for the late reply as I was busy with other important tasks. > > When you said panic, you mean a system hang, not an actual panic. Right?
Hi ,
Our setups turn on all the panic on-hung-task , on-opps, all those various features:
./sys/kernel/hardlockup_panic ./sys/kernel/hung_task_panic ./sys/kernel/max_rcu_stall_to_panic ./sys/kernel/panic ./sys/kernel/panic_on_io_nmi ./sys/kernel/panic_on_oops ./sys/kernel/panic_on_rcu_stall ./sys/kernel/panic_on_unrecovered_nmi ./sys/kernel/panic_on_warn ./sys/kernel/panic_print ./sys/kernel/softlockup_panic ./sys/kernel/unknown_nmi_panic
The machine is unusable when this occurs.
> > >> PID: 3789 TASK: ffff900fc409b300 CPU: 29 COMMAND: "dio/dm-0" >> #0 [fffffe00006bce50] crash_nmi_callback at ffffffff97c772c3 >> #1 [fffffe00006bce58] nmi_handle at ffffffff97c40778 >> #2 [fffffe00006bcea0] default_do_nmi at ffffffff988161e2 >> #3 [fffffe00006bcec8] exc_nmi at ffffffff9881648d >> #4 [fffffe00006bcef0] end_repeat_nmi at ffffffff98a0153b >> [exception RIP: _raw_spin_lock_irq+35] >> RIP: ffffffff98827333 RSP: ffffa9320917fc78 RFLAGS: 00000046 >> RAX: 0000000000000000 RBX: ffff900fc409b300 RCX: 0000000000000000 >> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 >> RBP: ffffa9320917fd20 R8: 0000000000000000 R9: 0000000000000000 >> R10: 0000000000000000 R11: 0000000000000000 R12: ffff90006259546c >> R13: ffffa9320917fcb0 R14: ffff900062595458 R15: 0000000000000000 >> ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018 >> --- <NMI exception stack> --- >> #5 [ffffa9320917fc78] _raw_spin_lock_irq at ffffffff98827333 >> #6 [ffffa9320917fc78] rwsem_down_write_slowpath at ffffffff97d25d49 >> #7 [ffffa9320917fd28] ext4_map_blocks at ffffffffc104b6dc [ext4] >> #8 [ffffa9320917fd98] ext4_convert_unwritten_extents at >> ffffffffc10369e0 [ext4] >> #9 [ffffa9320917fdf0] ext4_dio_write_end_io at ffffffffc103b2aa [ext4] >> #10 [ffffa9320917fe18] iomap_dio_complete at ffffffff98013f45 >> #11 [ffffa9320917fe48] iomap_dio_complete_work at ffffffff98014047 >> #12 [ffffa9320917fe60] process_one_work at ffffffff97cd9191 >> #13 [ffffa9320917fea8] rescuer_thread at ffffffff97cd991b >> #14 [ffffa9320917ff10] kthread at ffffffff97ce11f7 >> #15 [ffffa9320917ff50] ret_from_fork at ffffffff97c04cf2 >> crash> >> >> >> The failure is observed running "fio test suite" as a 24 hour soak >> test on an LVM composed of four NVME devices, Intel 72 core server. >> The test cycles through a variety of file-system types. >> >> >> This kernel has these commits >> >> 1ee326196c6658 locking/rwsem: Always try to wake waiters in >> out_nolock path >> >> d257cc8cb8d5 ("locking/rwsem: Make handoff bit handling more consistent") >> >> In earlier testing I had reverted d257cc8cb8d5 and did not observe >> said panics. I still feel d257cc8cb8d5 is still the root cause. > > So it is possible that 1ee326196c6658 does not completely eliminate the > missed wakeup situation. > > Regards, > Longman >
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