linux-kernel - Re: [RFC PATCH 01/10] thread_info: add helpers to snapshot thread flags

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Message-ID: <87h7hth4ln.ffs@nanos.tec.linutronix.de>
Date:   Sun, 20 Jun 2021 00:28:04 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Mark Rutland <mark.rutland@....com>, linux-kernel@...r.kernel.org
Cc:     benh@...nel.crashing.org, boqun.feng@...il.com, bp@...en8.de,
        catalin.marinas@....com, dvyukov@...gle.com, elver@...gle.com,
        ink@...assic.park.msu.ru, jonas@...thpole.se,
        juri.lelli@...hat.com, linux@...linux.org.uk, luto@...nel.org,
        mark.rutland@....com, mattst88@...il.com, mingo@...hat.com,
        monstr@...str.eu, mpe@...erman.id.au, paulmck@...nel.org,
        paulus@...ba.org, peterz@...radead.org, rth@...ddle.net,
        shorne@...il.com, stefan.kristiansson@...nalahti.fi,
        vincent.guittot@...aro.org, will@...nel.org
Subject: Re: [RFC PATCH 01/10] thread_info: add helpers to snapshot thread flags

On Wed, Jun 09 2021 at 13:19, Mark Rutland wrote:
> We have common helpers to manipulate individual thread flags, but where
> code wants to check several flags at once, it must open code reading
> current_thread_info()->flags and operating on a snapshot.

Who's we?

> As some flags can be set remotely it's necessary to use READ_ONCE() to
> get a consistent snapshot even when IRQs are disabled, but some code
> forgets to do this. Generally this is unlike to cause a problem in
> practice, but it is somewhat unsound, and KCSAN will legitimately warn
> that there is a data race.
>
> To make it easier to do the right thing, and to highlight that
> concurrent modification is possible, let's add a new helpers to
> snapshot

let's add? Why not simply "add"?

> +static inline unsigned long read_ti_thread_flags(struct thread_info *ti)

__always_inline() as Marco pointed out already

Other than those nitpicks:

 Reviewed-by: Thomas Gleixner <tglx@...utronix.de>