From: Petr Mladek <pmladek@suse.com> To: David Laight <David.Laight@aculab.com> Cc: Sergey Senozhatsky <senozhatsky@chromium.org>, John Ogness <john.ogness@linutronix.de>, Peter Geis <pgwipeout@gmail.com>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, "open list:ARM/Rockchip SoC..." <linux-rockchip@lists.infradead.org> Subject: Re: [BUG] Threaded printk breaks early debugging Date: Tue, 14 Jun 2022 10:37:13 +0200 [thread overview] Message-ID: <YqhIuTj+KAAA15J7@alley> (raw) In-Reply-To: <c81870cef50f4e1fac5083f0b780983d@AcuMS.aculab.com> On Mon 2022-06-13 16:11:19, David Laight wrote: > From: Petr Mladek > > Sent: 13 June 2022 11:14 > ... > > Another interesting alternative is the Peter Zijlstra's mode > > where all messages are printed to the console "immediately". > > They are serialized only by the CPU-reentrant lock. > > > > This mode is not good for production system. But it might > > be good for debugging. The good thing is that the behavior > > is well defined. > > ISTM that all messages should be output (even if this means > that cpu spin waiting for a serial console) until userspace > has a chance to set an option to change the behaviour. There are systems that do not boot because of softlockups caused by slow consoles. I am pretty sure that we will add the option to disable printk kthreads sooner or later. But we prefer to improve the code so that it works out of box. If we add the option already know then people will disable kthreads and do not report problematic scenarios. > Oh, and can someone stop the distros hiding the console output. > I want to see the 'oops' traceback when I break the kernel! Different users have different needs. AFAIK, distros hide the messages because they scare users and overload support. It is probably more effective to enable them only for debugging when users notice some malfunction. I do not know the details. I guess that there were years of evolution. The default in SUSE was probably set by some project managers or people taking care of boot splash, installation, ... Best Regards, Petr
WARNING: multiple messages have this Message-ID (diff)
From: Petr Mladek <pmladek@suse.com> To: David Laight <David.Laight@aculab.com> Cc: Sergey Senozhatsky <senozhatsky@chromium.org>, John Ogness <john.ogness@linutronix.de>, Peter Geis <pgwipeout@gmail.com>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, "open list:ARM/Rockchip SoC..." <linux-rockchip@lists.infradead.org> Subject: Re: [BUG] Threaded printk breaks early debugging Date: Tue, 14 Jun 2022 10:37:13 +0200 [thread overview] Message-ID: <YqhIuTj+KAAA15J7@alley> (raw) In-Reply-To: <c81870cef50f4e1fac5083f0b780983d@AcuMS.aculab.com> On Mon 2022-06-13 16:11:19, David Laight wrote: > From: Petr Mladek > > Sent: 13 June 2022 11:14 > ... > > Another interesting alternative is the Peter Zijlstra's mode > > where all messages are printed to the console "immediately". > > They are serialized only by the CPU-reentrant lock. > > > > This mode is not good for production system. But it might > > be good for debugging. The good thing is that the behavior > > is well defined. > > ISTM that all messages should be output (even if this means > that cpu spin waiting for a serial console) until userspace > has a chance to set an option to change the behaviour. There are systems that do not boot because of softlockups caused by slow consoles. I am pretty sure that we will add the option to disable printk kthreads sooner or later. But we prefer to improve the code so that it works out of box. If we add the option already know then people will disable kthreads and do not report problematic scenarios. > Oh, and can someone stop the distros hiding the console output. > I want to see the 'oops' traceback when I break the kernel! Different users have different needs. AFAIK, distros hide the messages because they scare users and overload support. It is probably more effective to enable them only for debugging when users notice some malfunction. I do not know the details. I guess that there were years of evolution. The default in SUSE was probably set by some project managers or people taking care of boot splash, installation, ... Best Regards, Petr _______________________________________________ Linux-rockchip mailing list Linux-rockchip@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-rockchip
next prev parent reply other threads:[~2022-06-14 8:38 UTC|newest] Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-06-10 12:48 [BUG] Threaded printk breaks early debugging Peter Geis 2022-06-10 12:48 ` Peter Geis 2022-06-10 15:05 ` John Ogness 2022-06-10 15:05 ` John Ogness 2022-06-10 15:34 ` Peter Geis 2022-06-10 15:34 ` Peter Geis 2022-06-12 2:57 ` Sergey Senozhatsky 2022-06-12 2:57 ` Sergey Senozhatsky 2022-06-12 13:30 ` Peter Geis 2022-06-12 13:30 ` Peter Geis 2022-06-12 23:08 ` John Ogness 2022-06-12 23:08 ` John Ogness 2022-06-12 23:30 ` Peter Geis 2022-06-12 23:30 ` Peter Geis 2022-06-13 2:23 ` John Ogness 2022-06-13 2:23 ` John Ogness 2022-06-13 15:11 ` Petr Mladek 2022-06-13 15:11 ` Petr Mladek 2022-06-13 22:20 ` Peter Geis 2022-06-13 22:20 ` Peter Geis 2022-06-14 8:38 ` Petr Mladek 2022-06-14 8:38 ` Petr Mladek 2022-06-13 11:24 ` Petr Mladek 2022-06-13 11:24 ` Petr Mladek 2022-06-12 3:13 ` Sergey Senozhatsky 2022-06-12 3:13 ` Sergey Senozhatsky 2022-06-12 23:02 ` John Ogness 2022-06-12 23:02 ` John Ogness 2022-06-13 3:49 ` Sergey Senozhatsky 2022-06-13 3:49 ` Sergey Senozhatsky 2022-06-13 8:30 ` John Ogness 2022-06-13 8:30 ` John Ogness 2022-06-13 9:05 ` Sergey Senozhatsky 2022-06-13 9:05 ` Sergey Senozhatsky 2022-06-13 10:14 ` Petr Mladek 2022-06-13 10:14 ` Petr Mladek 2022-06-13 16:11 ` David Laight 2022-06-13 16:11 ` David Laight 2022-06-14 8:37 ` Petr Mladek [this message] 2022-06-14 8:37 ` Petr Mladek
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