Messages in this thread | | | Date | Tue, 26 Apr 2022 16:21:25 -0400 | Subject | Re: [PATCH v5] locking/rwsem: Make handoff bit handling more consistent | From | Waiman Long <> |
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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?
> 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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