From nobody Wed Sep 3 06:01:27 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A6F07C38A2D for ; Mon, 24 Oct 2022 12:27:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233670AbiJXM1O (ORCPT ); Mon, 24 Oct 2022 08:27:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60566 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231238AbiJXM0r (ORCPT ); Mon, 24 Oct 2022 08:26:47 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B328583233; Mon, 24 Oct 2022 05:01:04 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 91AE9B81199; Mon, 24 Oct 2022 11:55:43 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E02B7C433C1; Mon, 24 Oct 2022 11:55:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1666612542; bh=HvNQLbDFpQyKb6hj8OG6baMZ1QDProYxanDCjhbgJvM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=JYbh09bNAZ7/T/ysJOIMz7/xfGSSAQDtPcLbFN21KshsU2dS62qpUlqoq5X3iZ6Pv u4KPuoCDcN7zHAit47Gz8xg8oLZiU8FgQEYikuW8xsLeFisZhu5u27oRVVqJCNeWzA LQkFm9og4z+o13cD3iyvp76AJkDlnxjE0q1fYyXU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Sebastian Andrzej Siewior , "Jason A. Donenfeld" Subject: [PATCH 4.19 027/229] random: avoid reading two cache lines on irq randomness Date: Mon, 24 Oct 2022 13:29:06 +0200 Message-Id: <20221024113000.011600600@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221024112959.085534368@linuxfoundation.org> References: <20221024112959.085534368@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Jason A. Donenfeld commit 9ee0507e896b45af6d65408c77815800bce30008 upstream. In order to avoid reading and dirtying two cache lines on every IRQ, move the work_struct to the bottom of the fast_pool struct. add_ interrupt_randomness() always touches .pool and .count, which are currently split, because .mix pushes everything down. Instead, move .mix to the bottom, so that .pool and .count are always in the first cache line, since .mix is only accessed when the pool is full. Fixes: 58340f8e952b ("random: defer fast pool mixing to worker") Reviewed-by: Sebastian Andrzej Siewior Signed-off-by: Jason A. Donenfeld Signed-off-by: Greg Kroah-Hartman --- drivers/char/random.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -890,10 +890,10 @@ void __init add_bootloader_randomness(co } =20 struct fast_pool { - struct work_struct mix; unsigned long pool[4]; unsigned long last; unsigned int count; + struct work_struct mix; }; =20 static DEFINE_PER_CPU(struct fast_pool, irq_randomness) =3D {