From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf1-x443.google.com ([2607:f8b0:4864:20::443]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1gMYma-0001my-8C for linux-um@lists.infradead.org; Tue, 13 Nov 2018 13:31:09 +0000 Received: by mail-pf1-x443.google.com with SMTP id g7-v6so6054281pfo.10 for ; Tue, 13 Nov 2018 05:30:57 -0800 (PST) Subject: Re: New Patch series for the UBD Driver References: <20181112174201.12290-1-anton.ivanov@cambridgegreys.com> <62f14981-9804-8fac-c3ec-b544a90751c3@kernel.dk> <58614d39-8c3b-4e8e-7b41-633bb52b533e@cambridgegreys.com> <880075e6-1032-fe4f-0001-085d7409eb54@kernel.dk> <2b318d17-7fde-991b-fda4-271fde2a7db9@kernel.dk> <0e31d0a6-64f0-208e-bfc8-acd05db432f1@cambridgegreys.com> <1d334c50-0f89-70e7-b6c7-fe0d719ed5df@cambridgegreys.com> <1e27868d-974b-9554-1010-a7e28a238479@kernel.dk> <17fab2bf-416b-3c61-e5c6-d315fb9105b3@kernel.dk> <651eb31c-4f75-0174-cd1a-a045d8d93991@cambridgegreys.com> From: Jens Axboe Message-ID: <1d7151d0-62b7-000c-c506-7b321bf788bb@kernel.dk> Date: Tue, 13 Nov 2018 06:30:53 -0700 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-um" Errors-To: linux-um-bounces+geert=linux-m68k.org@lists.infradead.org To: Anton Ivanov , linux-um@lists.infradead.org Cc: richard@nod.at, hch@lst.de On 11/13/18 3:15 AM, Anton Ivanov wrote: > I have figured out part of it. It is not caused by the block layer at > all. The offending parts are printks in the io thread. You simply cannot > printk out of there, that causes the spinlock recursion, irqs, on/off, > etc warning. > > This means that any errors MUST be reported only after they have gone > back to the main UML kernel thread. That's a pretty serious issue with UML, there's absolutely nothing wrong with doing printk from IRQ context, or from an IO thread like this one. You don't know what the call stack below you will do for functions you call, this is a ticking time bomb. -- Jens Axboe _______________________________________________ linux-um mailing list linux-um@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-um