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Groups > linux.debian.kernel > #60253

Bug#804857: CONFIG_RCU_NOCB_CPU?

From Hillel Lubman <shmerl@mykolab.com>
Newsgroups linux.debian.bugs.dist, linux.debian.kernel
Subject Bug#804857: CONFIG_RCU_NOCB_CPU?
Date 2018-02-21 03:10 +0100
Message-ID <vls14-r1-5@gated-at.bofh.it> (permalink)
References <qtZXc-VN-13@gated-at.bofh.it>
Organization linux.* mail to news gateway

Cross-posted to 2 groups.

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On Thu, 12 Nov 2015 17:29:35 +0000 Ben Hutchings <ben@decadent.org.uk> wrote:
>
> But for other configurations it is worse:
> 
> config NO_HZ_FULL
>         bool "Full dynticks system (tickless)"
> ...
>          This is implemented at the expense of some overhead in user <-> kernel
>          transitions: syscalls, exceptions and interrupts. Even when it's
>          dynamically off.
> 
>          Say N.
> 
> I think we should enable this for the rt featureset when it's next
> available, but not by default.
> 
> Ben.

What about CONFIG_RCU_NOCB_CPU? There is currently a nasty hardware freeze / reboot bug that
affects AMD Ryzen CPUs on Linux: https://bugzilla.kernel.org/show_bug.cgi?id=196683[1] 

Many report, that setting rcu-nocbs kernel parameter works around it at least partially, but it requires
the kernel to be built with CONFIG_RCU_NOCB_CPU=Y. Can it be enabled in Debian, or there are reasons
not to do it?

Thanks!
Hillel.

--------
[1] https://bugzilla.kernel.org/show_bug.cgi?id=196683

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Thread

Bug#804857: linux: New feature: enable CONFIG_NO_HZ_FULL and CONFIG_RCU_NOCB_CPU/CONFIG_RCU_NOCB_CPU_NONE Quentin Deldycke <quentindeldycke@gmail.com> - 2015-11-12 14:20 +0100
  Bug#804857: linux: New feature: enable CONFIG_NO_HZ_FULL and CONFIG_RCU_NOCB_CPU/CONFIG_RCU_NOCB_CPU_NONE Ben Hutchings <ben@decadent.org.uk> - 2015-11-12 18:40 +0100
  Bug#804857: CONFIG_RCU_NOCB_CPU? Hillel Lubman <shmerl@mykolab.com> - 2018-02-21 03:10 +0100
  Bug#804857: linux: New feature: enable CONFIG_NO_HZ_FULL and CONFIG_RCU_NOCB_CPU/CONFIG_RCU_NOCB_CPU_NONE Witold Baryluk <witold.baryluk@gmail.com> - 2018-11-14 19:10 +0100
  Bug#804857: RE OECIPOLLETTI <OECIPOLLETTI@trabajo.gob.ar> - 2019-07-11 10:50 +0200

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