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From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: Tony Luck <tony.luck@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Ted Ts'o" <tytso@mit.edu>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] random: always use batched entropy for get_random_u{32,64}
Date: Fri, 21 Feb 2020 21:08:19 +0100	[thread overview]
Message-ID: <CAHmME9q1rnD5z2bENYhqnM5-XCD+E68nm2RrGRWXt8ntpvfezg@mail.gmail.com> (raw)
In-Reply-To: <CA+8MBbKyRhipHsxb0nvV11Bvv8ypQ_gq5JR8ihfuG6JfBTnxZw@mail.gmail.com>

On Thu, Feb 20, 2020 at 11:29 PM Tony Luck <tony.luck@gmail.com> wrote:
>
> Also ... what's the deal with a spin_lock on a per-cpu structure?
>
>         batch = raw_cpu_ptr(&batched_entropy_u64);
>         spin_lock_irqsave(&batch->batch_lock, flags);
>         if (batch->position % ARRAY_SIZE(batch->entropy_u64) == 0) {
>                 extract_crng((u8 *)batch->entropy_u64);
>                 batch->position = 0;
>         }
>         ret = batch->entropy_u64[batch->position++];
>         spin_unlock_irqrestore(&batch->batch_lock, flags);
>
> Could we just disable interrupts and pre-emption around the entropy extraction?

Probably, yes... We can address this in a separate patch.

  reply	other threads:[~2020-02-21 20:08 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-16 16:18 Jason A. Donenfeld
2020-02-16 18:23 ` Greg Kroah-Hartman
2020-02-20 22:20   ` Tony Luck
2020-02-20 22:29     ` Tony Luck
2020-02-21 20:08       ` Jason A. Donenfeld [this message]
2020-02-22  0:41         ` Theodore Y. Ts'o
2020-02-22  9:59           ` Jason A. Donenfeld
2020-02-24 20:41           ` Luck, Tony
2020-02-21 20:07     ` Jason A. Donenfeld
2020-02-21 20:10       ` [PATCH v2] " Jason A. Donenfeld
2020-02-28  4:09         ` Theodore Y. Ts'o
2020-04-01 13:08         ` Nicolai Stange

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