Re: rcu stalls during fstests runs for xfs

[Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>]

Cc+: Thomas,

On Jan 30, 2026 / 20:16, Shin'ichiro Kawasaki wrote:
> On Jan 29, 2026 / 15:19, Paul E. McKenney wrote:
> [...]
> > And Thomas Gleixner posted an alleged fix to the CID issue here:
> > 
> > https://lore.kernel.org/lkml/20260129210219.452851594@kernel.org/
> > 
> > Please let him know whether or not it helps.
> 
> Good to see this fix candidate series, thanks :) I have set up the patches and
> started my regular test runs. So far, the hangs have been observed once or twice
> a week. To confirm the effect of the fix series, I think two weeks runs will be
> required. Once I get the result, will share it on this thread and with Thomas.

Two weeks have passed, and I did not observed the hang! Then I'm confident that
the v1 fix series by Thomas avoided the rcu stall issue in my xfs-zoned test
systems. The series is already in v6.19 kernel tag as v2. Great.

Thomas, just FYI.

I faced mysterious kernel hangs during my regular fstests runs [1]. RCU experts
suggested the hangs might be caused by the recent MMCID changes. I tried your v1
fix patch series "sched/mmcid: Cure mode transition woes", and confirmed it
avoids the hangs. Thank you for the fix. The v2 series is already in v6.19
kernel tag, so this report might not be so valuable, but just in case. (And
thank you again for the additional quick fix for my blktests failure caused by
one of the patches in the series).

[1] https://lore.kernel.org/rcu/aXdO52wh2rqTUi1E@shinmob/