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 EE6C4C43331 for ; Thu, 5 Sep 2019 17:14:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CE01A218AE for ; Thu, 5 Sep 2019 17:14:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387690AbfIEROW (ORCPT ); Thu, 5 Sep 2019 13:14:22 -0400 Received: from mail.kernel.org ([198.145.29.99]:42636 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729945AbfIEROV (ORCPT ); Thu, 5 Sep 2019 13:14:21 -0400 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 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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