linux-kernel - Re: [PATCH 00/30] PREEMPT_AUTO: support lazy rescheduling

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Date: Wed, 14 Feb 2024 18:03:28 -0800
From: Ankur Arora <ankur.a.arora@...cle.com>
To: paulmck@...nel.org
Cc: Ankur Arora <ankur.a.arora@...cle.com>, linux-kernel@...r.kernel.org,
        tglx@...utronix.de, peterz@...radead.org,
        torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
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Subject: Re: [PATCH 00/30] PREEMPT_AUTO: support lazy rescheduling


Paul E. McKenney <paulmck@...nel.org> writes:

> On Mon, Feb 12, 2024 at 09:55:24PM -0800, Ankur Arora wrote:
>> Hi,
>>
>> This series adds a new scheduling model PREEMPT_AUTO, which like
>> PREEMPT_DYNAMIC allows dynamic switching between a none/voluntary/full
>> preemption model. However, unlike PREEMPT_DYNAMIC, it doesn't depend
>> on explicit preemption points for the voluntary models.
>>
>> The series is based on Thomas' original proposal which he outlined
>> in [1], [2] and in his PoC [3].
>>
>> An earlier RFC version is at [4].
>
> This uncovered a couple of latent bugs in RCU due to its having been
> a good long time since anyone built a !SMP preemptible kernel with
> non-preemptible RCU.  I have a couple of fixes queued on -rcu [1], most
> likely for the merge window after next, but let me know if you need
> them sooner.

Thanks. As you can probably tell, I skipped out on !SMP in my testing.
But, the attached diff should tide me over until the fixes are in.

> I am also seeing OOM conditions during rcutorture testing of callback
> flooding, but I am still looking into this.

That's on the PREEMPT_AUTO && PREEMPT_VOLUNTARY configuration?

Thanks

--
ankur