From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 741BFC11D00 for ; Thu, 20 Feb 2020 22:29:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2EF08206F4 for ; Thu, 20 Feb 2020 22:29:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Jcjpzc7E" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729158AbgBTW3p (ORCPT ); Thu, 20 Feb 2020 17:29:45 -0500 Received: from mail-qt1-f195.google.com ([209.85.160.195]:44020 "EHLO mail-qt1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727845AbgBTW3o (ORCPT ); Thu, 20 Feb 2020 17:29:44 -0500 Received: by mail-qt1-f195.google.com with SMTP id g21so4108778qtq.10 for ; Thu, 20 Feb 2020 14:29:44 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=9JBTeYjQ4OSxmuiL2ZqLwcDcFNG9wOe01nNDIgFt4X8=; b=Jcjpzc7EBrfLq2tuPgjvbEzIeeVuOA4sAvis/RvWvv/Brx1gksKftAVO1KFKzvpy8z XCC6EJY3G5JHV132lV1wCm7LN1f/rfmt3+CH4EjSPI+zAqxp95FAfYm78JB7z2zLcnjP gP0g8gVAg4LUlFpnBhuUnZWh5uuqRb+EMzAj+dK9o7cZx7I9EZ62x0+G6D1oWAmsNYoK NqoSZlefuuuXNQLbRqB0WCf10W3Pj/SPDuDukffuQl43IFMudS1AXuu3aDEjB+QnU1vs 76oVvCXEpK9RHZXVjNzKRAL5u+rHJ1RYSrZfcICqlgQS4cAdEgk4uj27yWO3v8QVTcFj fPrQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=9JBTeYjQ4OSxmuiL2ZqLwcDcFNG9wOe01nNDIgFt4X8=; b=aj1Qjc0ik2RyNXQqz5wuy6eLRMOBtcmX62Q9imCzuByQzMwO9tgnO3acArxOcyl3+B LjjC0rWfjCuvXxHBUokHCwWN/3fx+KxKJg0eDjP2LqqRybuUTbgmj8VNmPovZOlZlW3v 1MoJFUrJldCM38DC2nA3Ppy4TYTT6813DIzZ7y5VmXBYgJzpJ83Pe8XLzbVZmX865u6Y vf5TBihL7tvNFQ4WL/zlTqIn1DGEBPSlQatmmf70UDDSQi2XjX6XEOvtfXW0+fr4UNSr XErkFSMAChzyOwLSSbMCpRhavNmPwfn65GZ6z7QJQIEBt6e/VxnG+2o9rCVgWFKbgkjl X/2g== X-Gm-Message-State: APjAAAWWfYFR/ha9qoyzAVCXJE3hkGbDBdvnaDBIUkozrQyn9qEDTwu/ A7oftqfhzQbTFpdLvHpqaeI8OY6au+OIP/oLnK6oZ2sc X-Google-Smtp-Source: APXvYqwoWrH7/If0ame9SZaVwZx3aYtuG3KUWXrbZCSZ/1HYk27oz6ttjY7BHfQHj8CWFY3vOIj4TG728lbd0zUqX2I= X-Received: by 2002:ac8:381a:: with SMTP id q26mr29289352qtb.381.1582237783761; Thu, 20 Feb 2020 14:29:43 -0800 (PST) MIME-Version: 1.0 References: <20200216161836.1976-1-Jason@zx2c4.com> <20200216182319.GA54139@kroah.com> In-Reply-To: From: Tony Luck Date: Thu, 20 Feb 2020 14:29:32 -0800 Message-ID: Subject: Re: [PATCH] random: always use batched entropy for get_random_u{32,64} To: Greg Kroah-Hartman Cc: "Jason A. Donenfeld" , "Ted Ts'o" , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Also ... what's the deal with a spin_lock on a per-cpu structure? batch = raw_cpu_ptr(&batched_entropy_u64); spin_lock_irqsave(&batch->batch_lock, flags); if (batch->position % ARRAY_SIZE(batch->entropy_u64) == 0) { extract_crng((u8 *)batch->entropy_u64); batch->position = 0; } ret = batch->entropy_u64[batch->position++]; spin_unlock_irqrestore(&batch->batch_lock, flags); Could we just disable interrupts and pre-emption around the entropy extraction? -Tony