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=-7.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,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 5F90FC433FE for ; Sat, 5 Dec 2020 04:41:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 112D922581 for ; Sat, 5 Dec 2020 04:40:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727245AbgLEEki (ORCPT ); Fri, 4 Dec 2020 23:40:38 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55616 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726011AbgLEEki (ORCPT ); Fri, 4 Dec 2020 23:40:38 -0500 Received: from mail-pj1-x102e.google.com (mail-pj1-x102e.google.com [IPv6:2607:f8b0:4864:20::102e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6234CC0613D1 for ; Fri, 4 Dec 2020 20:39:57 -0800 (PST) Received: by mail-pj1-x102e.google.com with SMTP id h7so4733943pjk.1 for ; Fri, 04 Dec 2020 20:39:57 -0800 (PST) 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; bh=dDsaAUqDcV3mkLWcdIvqwiC9jKLLEexcbhVFGjFuSCM=; b=TBa7hXSvL00GfYL1BJGGOgLClR65+euQ//6xwJHIXI2zw1mYaTHIAPTVhfxNJdYhxt PlzS4wUcik1uA7Hh0pcFMLmOAVRxmrBeZ0K5UET92VBOZI6q6gUckbmzRhxewIhoeBVW osPsrfLXkzLFHUMmJlEOon3+FImzaZ5dISCbSvD0D8V7Uk9T+6yGHg597Spg82bhb5X+ FL8J9nXA9uX7bEt8OyXyUREfhtoyIDgR9nNqhYTReShQHgNWdPGkTiIP+9ONu0dR2nDV qjKcJcb6BcRplTOtzGEbYn/D6A/cvRj2uJWUgNsfV6k0PaXN7AXKYzsVpDM8gw9BZNfj iyvg== 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; bh=dDsaAUqDcV3mkLWcdIvqwiC9jKLLEexcbhVFGjFuSCM=; b=XA6Bn5HJAR2Zwu9YOQe4w28E0q7CImAq/IMO/uv6s1x3VNtL8aCa8teNzhy4Finoxw THDiHTusym1jyCeU+sOvNQ1lVi296tHI/MrOdJAUzvUSygw7fnhnC53Nwk2EqBsqKYh9 0pkQ3K2cVOuVbR45z1le29f34ClWA6q074Sm70c3QYpJrYVmB6BCzP9zgAatAQQwC0tV F68eMQNFodbqjG03U9cPhih7DiauGJvxbQwGvTgOna2uM9iea88z2EFHVCYpA3la7k35 rZ8gUwSEk46UyePMFz6YCN1ht8wkFi1G2g/A6W5P/5v04XXIDRXV54fQ0FuEQHtNblwX Z1Ng== X-Gm-Message-State: AOAM5308P1ZkfuLQRlGhExbmMj7MRaCdJgNbifW/Gj+62zWBrYGN8IrL XFMgduIwiDtxXuM0MB/bYWo= X-Google-Smtp-Source: ABdhPJwZIgLcHEgOOAwIBaNkKYU8hih+hV8/z2jf5A/E4T9mOkJ47zDlEduMIjMNywDBWBCyOdxD1Q== X-Received: by 2002:a17:90a:1bc7:: with SMTP id r7mr3093003pjr.33.1607143196801; Fri, 04 Dec 2020 20:39:56 -0800 (PST) Received: from localhost ([2409:10:2e40:5100:6e29:95ff:fe2d:8f34]) by smtp.gmail.com with ESMTPSA id s30sm5462196pgl.39.2020.12.04.20.39.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 04 Dec 2020 20:39:55 -0800 (PST) Date: Sat, 5 Dec 2020 13:39:53 +0900 From: Sergey Senozhatsky To: Petr Mladek Cc: John Ogness , Sergey Senozhatsky , Sergey Senozhatsky , Steven Rostedt , Linus Torvalds , Greg Kroah-Hartman , Thomas Gleixner , linux-kernel@vger.kernel.org Subject: Re: consoles: was: [PATCH next v2 3/3] printk: remove logbuf_lock, add syslog_lock Message-ID: References: <20201201205341.3871-1-john.ogness@linutronix.de> <20201201205341.3871-4-john.ogness@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (20/12/04 17:19), Petr Mladek wrote: [..] > > --- a/kernel/printk/printk.c > > +++ b/kernel/printk/printk.c > > @@ -2432,7 +2490,6 @@ void console_unlock(void) > > size_t len; > > > > printk_safe_enter_irqsave(flags); > > Why do we actually need to use the printk_safe context here? > There is not longer a risk of deadlock caused by logbuf_lock. > All other recursions should be prevented by console_trylock() > in printk(). All semaphore functions, including down_trylock(), acquire semaphore spin_lock; and then some call into the scheduler (or other kernel core functions) under semaphore's spin_lock. For instance up() raw_spin_lock_irqsave(&sem->lock) __up() wake_up_process() try_to_wake_up() -ss