linux-kernel - Re: [PATCH v9 01/15] asm-generic: add barrier smp_cond_load_relaxed

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Message-ID: <Z0Wkr-BcSsSzFth8@arm.com>
Date: Tue, 26 Nov 2024 10:36:31 +0000
From: Catalin Marinas <catalin.marinas@....com>
To: Ankur Arora <ankur.a.arora@...cle.com>
Cc: linux-pm@...r.kernel.org, kvm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
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	boris.ostrovsky@...cle.com, konrad.wilk@...cle.com
Subject: Re: [PATCH v9 01/15] asm-generic: add barrier
 smp_cond_load_relaxed_timeout()

On Mon, Nov 25, 2024 at 09:01:56PM -0800, Ankur Arora wrote:
> Ankur Arora <ankur.a.arora@...cle.com> writes:
> > +/**
> > + * smp_cond_load_relaxed_timeout() - (Spin) wait for cond with no ordering
> > + * guarantees until a timeout expires.
> > + * @ptr: pointer to the variable to wait on
> > + * @cond: boolean expression to wait for
> > + * @time_expr_ns: evaluates to the current time
> > + * @time_limit_ns: compared against time_expr_ns
> > + *
> > + * Equivalent to using READ_ONCE() on the condition variable.
> > + *
> > + * Due to C lacking lambda expressions we load the value of *ptr into a
> > + * pre-named variable @VAL to be used in @cond.
> 
> Based on the review comments so far I'm planning to add the following
> text to this comment:
> 
>   Note that in the generic version the time check is done only coarsely
>   to minimize instructions executed while spin-waiting.
> 
>   Architecture specific variations might also have their own timeout
>   granularity.

Looks good.

> Meanwhile, would appreciate more reviews.

It's the middle of the merging window, usually not much review happens
unless they are fixes/regressions.

-- 
Catalin