From nobody Mon Dec 15 18:18:10 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 EC4D2ECAAA1 for ; Mon, 24 Oct 2022 11:58:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232377AbiJXL6k (ORCPT ); Mon, 24 Oct 2022 07:58:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56978 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232372AbiJXL5p (ORCPT ); Mon, 24 Oct 2022 07:57:45 -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 0FA3527CC0; Mon, 24 Oct 2022 04:47:15 -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 66E76B8113E; Mon, 24 Oct 2022 11:47:14 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BBFE0C433C1; Mon, 24 Oct 2022 11:47:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1666612033; bh=HvNQLbDFpQyKb6hj8OG6baMZ1QDProYxanDCjhbgJvM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mEepv6HdZeQNBz/rBs/aquBX05uRDqiFz/7Xuu2klhYj5/lCUyTtUlwZI01qqbnKQ IQRRVUVfYTu1W6ghmZIOVtAXm0QFNNRNpYqKnwBYdbT610uVzd1xpZNaEyW/Ht3vyH doMSIk39oT0yUjz4DgGIc9zfonSY0VipndQ+kySM= 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 4.14 045/210] random: avoid reading two cache lines on irq randomness Date: Mon, 24 Oct 2022 13:29:22 +0200 Message-Id: <20221024112958.456405677@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221024112956.797777597@linuxfoundation.org> References: <20221024112956.797777597@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 {