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 8CDAB4A4 for ; Thu, 20 Jul 2017 05:18:59 +0000 (UTC) Received: from mail-pg0-f52.google.com (mail-pg0-f52.google.com [74.125.83.52]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 36C4116B for ; Thu, 20 Jul 2017 05:18:59 +0000 (UTC) Received: by mail-pg0-f52.google.com with SMTP id s4so9596632pgr.5 for ; Wed, 19 Jul 2017 22:18:59 -0700 (PDT) Date: Thu, 20 Jul 2017 14:19:08 +0900 From: Sergey Senozhatsky To: Daniel Vetter Message-ID: <20170720051908.GB7483@jagdpanzerIV.localdomain> References: <20170619052146.GA2889@jagdpanzerIV.localdomain> <20170719062401.GA12064@jagdpanzerIV.localdomain> <20170719062538.GB12064@jagdpanzerIV.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Cc: "ksummit-discuss@lists.linuxfoundation.org" Subject: Re: [Ksummit-discuss] [TECH TOPIC] printk redesign List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On (07/19/17 09:26), Daniel Vetter wrote: [..] > > d'oh... the link... > > > > https://github.com/sergey-senozhatsky/printk-todo > > lgtm, two quick notes: > - my mail with the fbdev discussion seems to be in the wrong chapter. > Move it from "console_sem" to "fbdev, tty, drm, etc .."? thanks for taking a look! and sorry for not being very responsive these weeks, still struggling to recover from my sickness. the list is incomplete and very spontaneous, I'll improve it. > - feature request for per-console output: Per-console flag to always > use a kthread/offloading, even when oops/panic is happening. kms > definitely wants that. Please note that in that section. I can help > with implementing, once we get there. thanks. will add. > Per-console flag to always use a kthread/offloading, even when oops/panic > is happening. kms definitely wants that. > hmm... kthread offloading during panic() is really risky. nothing guarantees that we will be able to call into the scheduler and wake up that console printing-kthread, or that we will be able to schedule at all. we may be in panic() from NMI handler, with the rest of CPUs stopped. it's quite a risky thing to do. that's why we disable printk offloading when in panic() - we don't want to make the things any worse. before doing this I think I want to make call_console_drivers() to be more reliable. right now we pick the first unseen messages from the logbuf and iterate over registered consoles calling ->write() on every driver from the console drivers list. if one of consoles is misbehaving, then the entire console output mechanism stops: we don't print anything on other consoles until current con->write() returns. so probably I want to make it more independent. -ss