From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de ([195.135.220.15]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kx8Zr-00042K-MZ for linux-um@lists.infradead.org; Wed, 06 Jan 2021 13:10:16 +0000 Date: Wed, 6 Jan 2021 14:10:10 +0100 From: Petr Mladek Subject: Re: kunit stopped working Message-ID: References: <20201221144302.GR4077@smile.fi.intel.com> <20201221144510.GS4077@smile.fi.intel.com> <2d4b8148-48ca-290f-1d66-33e302e7571d@linuxfoundation.org> <20201221192757.GZ4077@smile.fi.intel.com> <20201221194008.GA4077@smile.fi.intel.com> <20201221200332.GB4077@smile.fi.intel.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: 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: Sergey Senozhatsky Cc: Sergey Senozhatsky , David Gow , Greg Kroah-Hartman , Brendan Higgins , linux-um , "open list:KERNEL SELFTEST FRAMEWORK" , Shuah Khan , Andy Shevchenko , Guenter Roeck , KUnit Development On Wed 2021-01-06 13:04:57, Sergey Senozhatsky wrote: > On (21/01/05 17:49), Petr Mladek wrote: > > The following change solved the problem for me as well. It causes > > that ttynull is initialized after stdiocons console. > > > > diff --git a/drivers/tty/ttynull.c b/drivers/tty/ttynull.c > > index eced70ec54e1..602af4d30bd4 100644 > > --- a/drivers/tty/ttynull.c > > +++ b/drivers/tty/ttynull.c > > @@ -121,7 +121,6 @@ static void __exit ttynull_exit(void) > > tty_port_destroy(&ttynull_port); > > } > > > > -module_init(ttynull_init); > > -module_exit(ttynull_exit); > > +late_initcall_sync(ttynull_init); > > > > MODULE_LICENSE("GPL v2"); > > > > But I am not completely sure that it is the right solution. > > Wow, hmm, puzzled. Why does it help? I have been as well. But it seems that I got it, see below. > > It is strange. Console should get registered only when > > it was added by add_preferred_console(). It means that > > ttynull_init() should not register by default. > [..] > > Some clue might be in stderr_console. It has > > to be explicitly unregistered to avoid staying as > > the default console, see unregister_stderr() in > > arch/um/drivers/stderr_console.c > > Hmm... Some random thoughts: > > Looking at arch/um/drivers/stderr_console.c - it doesn't have tty > driver and it doesn't register one. stderr_console.c is used only during early boot. stdio_console.c is the console that is supposed to print kunit test results. And it has tty driver. > But I still don't understand why the initcall patch helped. > Can you shed some light on it? The trick is that both stdio_init() and ttynull_init(): + call register_console() + the console has tty driver The first one is registered as a fallback when there is no preferred console (has_preferred_console()). It means that late_initcall_sync(ttynull_init) makes sense. We need to call register_console() from ttynull_init() so that it is registered when defined on the command line. But it should be the last chance to register a fallback console with tty binding. Alternative solution is to ignore ttynull as the fallback console in register_console(). I mean the following: diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index ffdd0dc7ec6d..cdb77903b0af 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -2816,8 +2816,12 @@ void register_console(struct console *newcon) * See if we want to use this console driver. If we * didn't select a console we take the first one * that registers here. + * + * Ignore ttynull console. It should be used only + * when explicitly configured or as an ultimate + * fallback when no better console gets registered at all. */ - if (!has_preferred_console) { + if (!has_preferred_console && strcmp(newcon->name, "ttynull") != 0) { if (newcon->index < 0) newcon->index = 0; if (newcon->setup == NULL || Best Regards, Petr _______________________________________________ linux-um mailing list linux-um@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-um