Re: the stuttering regression in 7.0: should I have done something different?

[John Paul Adrian Glaubitz]

Hi Thorsten,

On Thu, 2026-04-23 at 18:30 +0200, Thorsten Leemhuis wrote:
> FWIW, here is the rough timeline of the regression, just to be sure we
> are all on the same page:
> 
> * The regression I'm talking about is caused by d6e152d905bdb1
> ("clockevents: Prevent timer interrupt starvation") [authored:
> 2026-04-07 10:54:17; committed: 2026-04-10 22:45:38; next arrival:
> next-20260413; merged: 2026-04-12 19:01:55; v7.0 (2026-04-12 22:48:06)]
> 
> * On Monday and thus within 24 of the 7.0 release the first report about
> the regression came in and immediately mentioned that a revert was able
> to fix things:
> https://lore.kernel.org/all/68d1e9ac-2780-4be3-8ee3-0788062dd3a4@xxxxxxxxx/
> 
> * On Tuesday someone else confirmed the findings and mentioned that
> "several users" were seeing the problem:
> https://lore.kernel.org/all/aeb848aa-404a-40fb-bd41-329644623b1d@xxxxxxxxxxx/
> 
> * A few hours later (aka within 24 hours of the first report) Thomas had
> a rough fix ready https://lore.kernel.org/all/87340xfeje.ffs@tglx/ (yeah!)
> 
> * On Thursday the fix was committed to the tip tree:
> https://lore.kernel.org/all/177636758252.1323100.5283878386670888513.tip-bot2@tip-bot2/
> 
> * On Sunday I asked when the fix was going to be mainlined (with Linus
> in CC) -- I feared Greg would soon start preparing 7.0.1-rc1 and I
> wanted to ensure the fix was included there:
> https://lore.kernel.org/all/5cbb14d8-46f9-4197-917f-51da852d7500@xxxxxxxxxxxxx/
> 
> * On Monday morning (UTC) mingo submitted a PR wit the fix:
> https://lore.kernel.org/all/aeXYPt1FEbFRZNJf@xxxxxxxxx/
> 
> * On Monday Greg released 7.0.1-rc1 without the fix -- and a backport of
> the culprit was in the -rc1 of various earlier series. Thomas quickly
> told the stable team to not backport the culprit before the fix was
> mainlined https://lore.kernel.org/all/87pl3ten5y.ffs@tglx/
> 
> * On Monday night Linus merged the PR from mingo as 4096fd0e8eaea1
> ("clockevents: Add missing resets of the next_event_forced flag")
> [authored: 2026-04-14 22:55:01; committed: 2026-04-16 21:22:04; next
> arrival: next-20260417; merged: 2026-04-21 00:30:08; v7.0-post]
> 
> * On Tuesday morning I wrote a mail to Greg about including the fix in
> 7.0.1; Thomas round about the same time provided the necessary backport,
> which Greg then included out-of-band:
> https://lore.kernel.org/all/2026042105-malformed-probation-232b@gregkh/
> https://lore.kernel.org/all/87jyu0de2c.ffs@tglx/
> 
> * v7.0.1 is released on Wednesday, 2026-04-22 13:32:23

Tony Rodriguez from the SPARC community has observed the regression on SPARC as well
and proposed a fix to address it [1]. Not sure whether he has retested on the latest
commit of Linus' tree yet.

Tony, can you verify that 4096fd0e8eaea1 fixes the issue for you?

Adrian

> [1] https://github.com/sparclinux/issues/issues/79

-- 
 .''`.  John Paul Adrian Glaubitz
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