linux-kernel - Re: [PATCH v3] random: remove batched entropy locking

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Message-ID: <CAHmME9ocuYZeG4Eh2PC37wDAgbd8K4c80NpNadXbfrJ-NoGaqQ@mail.gmail.com>
Date:   Fri, 4 Feb 2022 17:12:15 +0100
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Andy Lutomirski <luto@...capital.net>,
        Boqun Feng <boqun.feng@...il.com>,
        Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Waiman Long <longman@...hat.com>,
        Sultan Alsawaf <sultan@...neltoast.com>,
        "Theodore Ts'o" <tytso@....edu>, Andy Lutomirski <luto@...nel.org>,
        Jonathan Neuschäfer <j.neuschaefer@....net>,
        LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v3] random: remove batched entropy locking

Hi Sebastian,

On Fri, Feb 4, 2022 at 4:57 PM Sebastian Andrzej Siewior
<bigeasy@...utronix.de> wrote:
> Does this compile and work?

It does, yes.

> From the looks of it, this should be:
>
>         local_lock_irqsave(&batched_entropy_u64.lock, flags);
>         batch = this_cpu_ptr(&batched_entropy_u64);

I wasn't aware you could reference percpu things statically like that
without going through the ptr helper. Anyway, I'll switch to yours, as
taking that lock prior seems better anyway.

>
> and we could do s/this_cpu_ptr/raw_cpu_ptr/

Ack.

Jason