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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 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 90845C43140 for ; Thu, 5 Sep 2019 17:14:25 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 3927420870 for ; Thu, 5 Sep 2019 17:14:24 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3927420870 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 21A5E6B0282; Thu, 5 Sep 2019 13:14:23 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 1CBFD6B0283; Thu, 5 Sep 2019 13:14:23 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0E1606B0285; Thu, 5 Sep 2019 13:14:23 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0229.hostedemail.com [216.40.44.229]) by kanga.kvack.org (Postfix) with ESMTP id DC5F86B0282 for ; Thu, 5 Sep 2019 13:14:22 -0400 (EDT) Received: from smtpin29.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with SMTP id 84DE2180AD7C3 for ; Thu, 5 Sep 2019 17:14:22 +0000 (UTC) X-FDA: 75901515564.29.tail40_605c838d1715f X-HE-Tag: tail40_605c838d1715f X-Filterd-Recvd-Size: 2623 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf39.hostedemail.com (Postfix) with ESMTP for ; Thu, 5 Sep 2019 17:14:22 +0000 (UTC) Received: from oasis.local.home (bl11-233-114.dsl.telepac.pt [85.244.233.114]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 8DB8820828; Thu, 5 Sep 2019 17:14:19 +0000 (UTC) Date: Thu, 5 Sep 2019 13:14:13 -0400 From: Steven Rostedt To: Qian Cai Cc: Sergey Senozhatsky , Petr Mladek , Sergey Senozhatsky , Michal Hocko , Eric Dumazet , davem@davemloft.net, netdev@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] net/skbuff: silence warnings under memory pressure Message-ID: <20190905131413.0aa4e4f1@oasis.local.home> In-Reply-To: <1567699393.5576.96.camel@lca.pw> References: <20190903185305.GA14028@dhcp22.suse.cz> <1567546948.5576.68.camel@lca.pw> <20190904061501.GB3838@dhcp22.suse.cz> <20190904064144.GA5487@jagdpanzerIV> <20190904065455.GE3838@dhcp22.suse.cz> <20190904071911.GB11968@jagdpanzerIV> <20190904074312.GA25744@jagdpanzerIV> <1567599263.5576.72.camel@lca.pw> <20190904144850.GA8296@tigerII.localdomain> <1567629737.5576.87.camel@lca.pw> <20190905113208.GA521@jagdpanzerIV> <1567699393.5576.96.camel@lca.pw> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000016, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, 05 Sep 2019 12:03:13 -0400 Qian Cai wrote: > > > and could deal with console hardware that involve irq_exit() anyway. > > > > printk->console_driver->write() does not involve irq. > > Hmm, from the article, > > https://en.wikipedia.org/wiki/Universal_asynchronous_receiver-transmitter > > "Since transmission of a single or multiple characters may take a long time > relative to CPU speeds, a UART maintains a flag showing busy status so that the > host system knows if there is at least one character in the transmit buffer or > shift register; "ready for next character(s)" may also be signaled with an > interrupt." I'm pretty sure all serial consoles do a busy loop on the UART and not use interrupts to notify when it's available. That would require an asynchronous implementation of printk() which would be quite complex to implement. -- Steve