From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Ogness Subject: Re: Serial console is causing system lock-up Date: Thu, 07 Mar 2019 09:34:37 +0100 Message-ID: <87pnr3hyle.fsf@linutronix.de> References: <20190306152218.eocv4zulf7tv2mkc@pathway.suse.cz> <20190306163003.GA31858@mit.edu> <20190306171943.12345598@oasis.local.home> <87ftrzbp3y.fsf@linutronix.de> <20190307022254.GB4893@jagdpanzerIV> <87tvgfhzd6.fsf@linutronix.de> <20190307082509.GA1925@jagdpanzerIV> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20190307082509.GA1925@jagdpanzerIV> (Sergey Senozhatsky's message of "Thu, 7 Mar 2019 17:25:09 +0900") List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: Sergey Senozhatsky Cc: Petr Mladek , Nigel Croxon , "Theodore Y. Ts'o" , Greg Kroah-Hartman , Steven Rostedt , Sergey Senozhatsky , dm-devel@redhat.com, Mikulas Patocka , linux-serial@vger.kernel.org List-Id: linux-serial@vger.kernel.org On 2019-03-07, Sergey Senozhatsky wrote: >>> If the serial console is a really slow one and we have a CPU in >>> atomic context spinnig on prb_lock, while the prb_lock is always >>> acquired by other CPUs, then it may look like a lock-up scenario. >> >> When the console is constantly printing messages, I wouldn't say that >> looks like a lock-up scenario. It looks like the system is busy >> printing critical information to the console (which it is). > > What if we have N tasks/CPUs calling printk() simultaneously? Then they take turns printing their messages to the console, spinning until they get their turn. This still is not and does not look like a lock-up. But I think you already know this, so I don't understand the reasoning behind asking the question. Maybe you could clarify what you are getting at. John Ogness