linux-kernel - Re: [PATCH] random: use offstack cpumask when necessary

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Message-ID: <aEhsekBWuP51sWRZ@zx2c4.com>
Date: Tue, 10 Jun 2025 11:33:46 -0600
From: "Jason A. Donenfeld" <Jason@...c4.com>
To: Arnd Bergmann <arnd@...nel.org>
Cc: Theodore Ts'o <tytso@....edu>, Arnd Bergmann <arnd@...db.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>, Eric Biggers <ebiggers@...gle.com>,
	Joel Granados <joel.granados@...nel.org>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] random: use offstack cpumask when necessary

Hi Arnd,

On Tue, Jun 10, 2025 at 11:27:08AM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> The entropy generation function keeps a local cpu mask on the stack, which
> can trigger warnings in configurations with a large number of CPUs:
> 
> drivers/char/random.c:1292:20: error: stack frame size (1288) exceeds limit (1280) in 'try_to_generate_entropy' [-Werror,-Wframe-larger-than]
> 
> Use the cpumask interface to dynamically allocate it in those configurations.

Thanks. I hadn't seen this interface before. Applied with one nit fixed:

> +		goto out;;

Double semi-colon changed to single semi-colon.

Jason