Messages in this thread | | | Date | Tue, 28 Feb 2023 00:40:38 +0100 | From | Frederic Weisbecker <> | Subject | Re: [PATCH RFC v2] rcu: Add a minimum time for marking boot as completed |
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On Mon, Feb 27, 2023 at 03:05:02PM -0800, Paul E. McKenney wrote: > On Mon, Feb 27, 2023 at 02:10:30PM -0500, Joel Fernandes wrote: > > The combination of sysfs manipulated by userspace and a kernel failsafe > makes sense to me. Especially if by default triggering the failsafe > splats. That way, bugs where userspace fails to update the sysfs file > get caught. > > The non-default silent-failsafe mode is also useful to allow some power > savings in advance of userspace getting the sysfs updating in place. > And of course the default splatting setup can be used in internal testing > with the release software being more tolerant of userspace foibles.
I'm wondering, this is all about CONFIG_RCU_LAZY, right? Or does also expedited GP turned off a bit early or late on boot matter for anybody in practice?
So shouldn't we disable lazy callbacks by default when CONFIG_RCU_LAZY=y and then turn it on with "sysctl kernel.rcu.lazy=1" only whenever userspace feels ready about it? We can still keep the current call to rcu_end_inkernel_boot().
And if suddenly disabling lazy by default is an ABI breakage we can still add CONFIG_RCU_LAZY_DEFAULT_DISABLED.
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