Messages in this thread | | | From | Linus Torvalds <> | Date | Tue, 12 Mar 2024 14:11:24 -0700 | Subject | Re: [GIT PULL] Networking for v6.9 |
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On Tue, 12 Mar 2024 at 13:47, Jakub Kicinski <kuba@kernel.org> wrote: > > With your tree as of 65d287c7eb1d it gets to prompt but dies soon after > when prod services kick in (dunno what rpm Kdump does but says iocost > so adding Tejun):
Both of your traces are timers that seem to either lock up in ioc_now():
https://lore.kernel.org/all/20240312133427.1a744844@kernel.org/
and now it looks like ioc_timer_fn():
https://lore.kernel.org/all/20240312134739.248e6bd3@kernel.org/
But in neither case does it actually look like it's a lockup on a *lock*.
IOW, the NMI isn't happening on some spin_lock sequence or anything like that.
Yes, ioc_now() could have been looping on the seq read-lock if the sequence number was odd. But the writers do seem to be done with interrupts disabled, plus then you wouldn't have this lockup in ioc_timer_fn, so it's probably not that.
And yes, ioc_timer_fn() does take locks, but again, that doesn't seem to be where it is hanging.
So it smells like it's an endless loop in ioc_timer_fn() to me, or perhaps retriggering the timer itself infinitely.
Which would then explain both of those traces (that endless loop would call ioc_now() as part of it).
The blk-iocost.c code itself hasn't changed, but the timer code has gone through big changes.
That said, there's a more blk-related change: da4c8c3d0975 ("block: cache current nsec time in struct blk_plug").
*And* your second dump is from that
period_vtime = now.vnow - ioc->period_at_vtime; if (WARN_ON_ONCE(!period_vtime)) {
so it smells like the blk-iocost code is just completely confused by the time caching. Jens?
Jakub, it might be worth seeing if just reverting that commit da4c8c3d0975 makes the problem go away. Otherwise a bisect might be needed...
Linus
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