linux-kernel - Re: [PATCH REPOST] random: Add a spinlock_t to struct batched

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Message-ID: <20190428182928.GD24089@mit.edu>
Date:   Sun, 28 Apr 2019 14:29:28 -0400
From:   "Theodore Ts'o" <tytso@....edu>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, tglx@...utronix.de
Subject: Re: [PATCH REPOST] random: Add a spinlock_t to struct batched_entropy

On Fri, Apr 26, 2019 at 12:34:38PM +0200, Sebastian Andrzej Siewior wrote:
> The per-CPU variable batched_entropy_uXX is protected by get_cpu_var().
> This is just a preempt_disable() which protects against concurrent
> access from process context on the local CPU. It does not protect
> against users on the same CPU from another context. It is possible that
> a preemptible context reads slot 0 and then an interrupt occurs and the
> same value is read again from hard or soft IRQ context.

This patch is already on the random.git tree.  (It wasn't in
linux-next because I had forgotten that linux-next pulls from the dev
branch, as opposed to the master branch.)

Cheers,

					- Ted