From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 1DBBE25A for ; Tue, 27 Oct 2015 23:52:58 +0000 (UTC) Received: from mail-pa0-f48.google.com (mail-pa0-f48.google.com [209.85.220.48]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id B1F0390 for ; Tue, 27 Oct 2015 23:52:57 +0000 (UTC) Received: by padhk11 with SMTP id hk11so236986457pad.1 for ; Tue, 27 Oct 2015 16:52:57 -0700 (PDT) Date: Wed, 28 Oct 2015 08:53:51 +0900 From: Sergey Senozhatsky To: Jiri Kosina Message-ID: <20151027235351.GA4885@swordfish> References: <562E37D7.9080105@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Cc: theodore.tso@gmail.com, ksummit-discuss@lists.linuxfoundation.org Subject: Re: [Ksummit-discuss] Late KS topics List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On (10/26/15 23:51), Jiri Kosina wrote: > On Mon, 26 Oct 2015, Hannes Reinecke wrote: > > > The talk/proposal should be used to come to a consensus about > > restricting printk() to high-priority, small volume messages, > > and implement a different call (like log_printk()) for the > > low-priority, high-volume traffic. > > The printk() troubles are not only about the "high volume" vs. "very > important", but also about the context of the caller. sometimes "high volume" and 'unlucky' printk_deferred() dynamic duo can do dramatic things. printk_deferred() queues a irq work - wake_up_klogd_work(), which does wake_up_klogd_work_func(): .. console_trylock() console_unlock() so we eventually end up in for (;;) { .. call_console_drivers() .. } -ss > The optimistic comment above printk() says that it can be called from any > context, but that's not true for quite some time already. > So if printk() is going to be redesigned to be more lightweight, this > aspect definitely needs to be taken into consideration as well.