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=-2.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 725A4C6778C for ; Tue, 3 Jul 2018 16:39:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 29C3621EF7 for ; Tue, 3 Jul 2018 16:39:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="c8Qw1VKT" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 29C3621EF7 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934166AbeGCQjy (ORCPT ); Tue, 3 Jul 2018 12:39:54 -0400 Received: from mail-pg0-f67.google.com ([74.125.83.67]:36588 "EHLO mail-pg0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933792AbeGCQjw (ORCPT ); Tue, 3 Jul 2018 12:39:52 -0400 Received: by mail-pg0-f67.google.com with SMTP id m19-v6so1228627pgv.3 for ; Tue, 03 Jul 2018 09:39:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=ww9geydn5pw5H66UgKWm+8622ROtlPir+hEl4qOoS1Y=; b=c8Qw1VKTCGXTS/qMoS4qS7v+HIR5FQIlEUkCVZLgTmUaJODJW0LLjPArNSi/hZkiWh +o34sxNYbma5YogPbCiV+NGEjxQSrylUJvpJ4eIsj+Kac2rjoOfC4U7RhyWPCgWptNAp KQPLfQHForubXl/EfjsA4XhlHyduuwJMhzIAH+rTQl5QB10Gs0H5NzBTtarhhtU8QEOT NcbtnQccCmIvPRO2zVL2LksaC4cILMUEOUEa6ZDe3AwLRxuM0Dd0EveVprYYMagYX5fs +ohYlfmdH5XRNIlv6HXFH/+0H46ZkCKcE868ph88AHaSRugazXAVc/BalR9pE9i7bQqB VFBg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=ww9geydn5pw5H66UgKWm+8622ROtlPir+hEl4qOoS1Y=; b=gSTwNFKOYXt5qmgN9GtJ6d58I3/2Xi1pSvu2ZqRl18y3mBuS3yfwcAwGRnU3ie4QzP n3CW/KSDX+mNMk701+llDGOp6MZUORVI3N3xtPdmLECA3iQbHPoKALsr2CtJfrW9aJHC St28ZW746ShpvUI1uOTTcAnwf13tSxf5elvMvf08uBGV/md35Fy61O9pXdw1Vc5dYgUl l+cVoUrhxi9gyzgtkKcuofoqKhHl2D9zauiLpyA3MfNWjaat4dWdLWXQfeEngy/MkvPD Sb3CGDzoNNe8i5LPeKe/4qFzxNAbUIZIGSNk+WxC7TMLGPPwaKl+nFMPJEOVvdjVmhHu SzrA== X-Gm-Message-State: APt69E0VqNHWvuDI/0z35ShdMD7/KVvxBwIyG4hKM6C74+igr+rPm9Ze l4AH9xAPicPyBJPnMjSGzbM= X-Google-Smtp-Source: AAOMgpfqWj6Q40fIN+T/INo43mywGLB8X5eKZ17OJH8GOhnXFUHA4p4AOstBmu9Gv25vJxhIrG0tzw== X-Received: by 2002:a62:b612:: with SMTP id j18-v6mr30619755pff.199.1530635991853; Tue, 03 Jul 2018 09:39:51 -0700 (PDT) Received: from localhost ([121.137.63.184]) by smtp.gmail.com with ESMTPSA id v6-v6sm9628213pfa.28.2018.07.03.09.39.50 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 03 Jul 2018 09:39:50 -0700 (PDT) Date: Wed, 4 Jul 2018 01:39:48 +0900 From: Sergey Senozhatsky To: Sergey Senozhatsky Cc: Tejun Heo , Sergey Senozhatsky , Tetsuo Handa , Steven Rostedt , Petr Mladek , Peter Zijlstra , Linus Torvalds , Andrew Morton , Dmitry Vyukov , linux-kernel@vger.kernel.org Subject: Re: printk() from NMI backtrace can delay a lot Message-ID: <20180703163948.GD391@tigerII.localdomain> References: <20180703043021.GA547@jagdpanzerIV> <20180703152944.GQ533219@devbig577.frc2.facebook.com> <20180703163145.GB391@tigerII.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180703163145.GB391@tigerII.localdomain> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (07/04/18 01:31), Sergey Senozhatsky wrote: > it might be the case that we can do > > serial_driver_handle_irq() > { > spin_loc(uart_port->lock); > > .. TX / RX > > spin_unlock(uart_port->lock); > > tty_flip_buffer_push(uart_port->tty_port); > } > > This should break this chain > > uart_port->lock -> pool->lock // -> sheduler/etc. > > > Can we do it? What am I missing? Hmm, and we actually have some serial drivers that do tty_filp_buffer_push() outside of uart_port->lock. For instance, drivers/tty/serial/efm32-uart.c irqreturn_t efm32_uart_rxirq(). -ss