linux-kernel - Re: [PATCH 05/30] sched: *_tsk_need_resched() now takes resched

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Message-ID: <8734tlhhez.ffs@tglx>
Date: Wed, 21 Feb 2024 18:10:44 +0100
From: Thomas Gleixner <tglx@...utronix.de>
To: Ankur Arora <ankur.a.arora@...cle.com>
Cc: linux-kernel@...r.kernel.org, peterz@...radead.org,
 torvalds@...ux-foundation.org, paulmck@...nel.org,
 akpm@...ux-foundation.org, luto@...nel.org, bp@...en8.de,
 dave.hansen@...ux.intel.com, hpa@...or.com, mingo@...hat.com,
 juri.lelli@...hat.com, vincent.guittot@...aro.org, willy@...radead.org,
 mgorman@...e.de, jpoimboe@...nel.org, mark.rutland@....com,
 jgross@...e.com, andrew.cooper3@...rix.com, bristot@...nel.org,
 mathieu.desnoyers@...icios.com, geert@...ux-m68k.org,
 glaubitz@...sik.fu-berlin.de, anton.ivanov@...bridgegreys.com,
 mattst88@...il.com, krypton@...ich-teichert.org, rostedt@...dmis.org,
 David.Laight@...LAB.COM, richard@....at, mjguzik@...il.com,
 jon.grimm@....com, bharata@....com, raghavendra.kt@....com,
 boris.ostrovsky@...cle.com, konrad.wilk@...cle.com, Ankur Arora
 <ankur.a.arora@...cle.com>
Subject: Re: [PATCH 05/30] sched: *_tsk_need_resched() now takes resched_t
 as param

On Tue, Feb 20 2024 at 14:37, Ankur Arora wrote:
> Thomas Gleixner <tglx@...utronix.de> writes:
>> On Mon, Feb 12 2024 at 21:55, Ankur Arora wrote:
>>
>> The subject line reads odd...
>>
>>> -static inline bool test_tsk_need_resched(struct task_struct *tsk)
>>> +static inline bool test_tsk_need_resched(struct task_struct *tsk, resched_t rs)
>>>  {
>>> -	return unlikely(test_tsk_thread_flag(tsk,TIF_NEED_RESCHED));
>>> +	if (IS_ENABLED(CONFIG_PREEMPT_AUTO) || rs == NR_now)
>>> +		return unlikely(test_tsk_thread_flag(tsk, tif_resched(rs)));
>>> +	else
>>> +		return false;
>>>  }
>>
>> Same like the others. This wants wrappers with now/lazy.
>
> So, when working on the scheduler changes, I found the simplest
> implementation was to define a function that takes into account
> current preemption mode, checks for idle, tick etc and returns
> the rescheduling policy, which __resched_curr() carries out.
>
> So, it would be useful to just pass the resched_t as a parameter
> instead of having now/lazy wrappers.

That's fine for specific functions which really need to handle the
rescheduling mode, but for all other random places having a nice wrapper
makes the code more readable.

Thanks,

        tglx