From nobody Fri Dec 19 20:34:00 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 2B657C4332F for ; Thu, 13 Oct 2022 18:05:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231301AbiJMSFt (ORCPT ); Thu, 13 Oct 2022 14:05:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34760 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231181AbiJMSDj (ORCPT ); Thu, 13 Oct 2022 14:03:39 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D303A157F5F; Thu, 13 Oct 2022 11:03:23 -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 dfw.source.kernel.org (Postfix) with ESMTPS id 4375461952; Thu, 13 Oct 2022 18:00:24 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4941FC43143; Thu, 13 Oct 2022 18:00:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1665684023; bh=wWxXNLldQJWjVR9cUWjf0UKYSuekCHsercakn8tOViM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=1eiYyJPoKshujY3RDf7cXo4GmJfJ//cnAvgJzt8StnPv3FyQ16sJIwwnHDtztK9eZ 3rgECIoaD6vidM7Azg0j9umeiMz5UJANTzlFg+qmlapPzprI0+kgkEBpSuMaL6/VqT tKOzBsleYnlXi61Qq/GEYkaYlXyXWTa7IUdvkQ2U= 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 5.19 18/33] random: avoid reading two cache lines on irq randomness Date: Thu, 13 Oct 2022 19:52:50 +0200 Message-Id: <20221013175145.887818528@linuxfoundation.org> X-Mailer: git-send-email 2.38.0 In-Reply-To: <20221013175145.236739253@linuxfoundation.org> References: <20221013175145.236739253@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 @@ -903,10 +903,10 @@ EXPORT_SYMBOL_GPL(unregister_random_vmfo #endif =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 {