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SubjectRe: [PATCH 5.10.162-rt78] Restore initialization of wake_q_sleeper.next in fork.c
On Mon, Mar 20, 2023 at 05:00:13PM -0300, Luis Claudio R. Goncalves wrote:
> On Mon, Mar 20, 2023 at 03:37:31PM -0400, Joe Korty wrote:
> > In the transition from 5.10.158-rt77 to 5.10.162-rt78,
> > the initialization of task_struct::wake_q_sleeper.next
> > was dropped. Restore it.
> >
> > This appears to be only a problem in 5.10. 5.15 does not
> > have wake_q_sleeper; 4.19 does have it but its initialization
> > there is still present.
> >
> > The 5.10.162-rt78 patch that damaged fork.c is:
> >
> > 0170-locking-rtmutex-add-sleeping-lock-implementation.patch
> >
> > I do not have a simple test that brings out this problem.
> > My test consists of a shell script and eight binaries,
> > all of which were written in Ada. strace shows that it
> > does a few thousand forks in rapid succession. One of the
> > forks stalls out, after which no fork after that returns.
> > Eventually the 122 second stallout occurs and a large
> > number of threads are shown to be waiting for tasklist
> > lock, either in do_exit or in copy_process. The kernel
> > .config has rt and many debug features enabled, lockdep
> > included.
>
> Joe, thank you for investigating that problem and for writing a patch.
>
> Earlier today Steffen Dirkwinkel sent a similar patch:
>
> https://lore.kernel.org/all/20230320080347.32434-1-linux@steffen.cc/
>
> Would you mind giving your ACK to his patch? I have that patch queued for
> my next build already.

Acked-by: Joe Korty <joe.korty@concurrent-rt.com>

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