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[125.30.117.167]) by smtp.gmail.com with ESMTPSA id g8sm3073746pfh.43.2020.01.29.07.12.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 29 Jan 2020 07:12:45 -0800 (PST) From: Sergey Senozhatsky X-Google-Original-From: Sergey Senozhatsky Date: Thu, 30 Jan 2020 00:12:43 +0900 To: Andy Shevchenko Cc: Sergey Senozhatsky , Sergey Senozhatsky , Petr Mladek , Steven Rostedt , linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 5/5] console: Introduce ->exit() callback Message-ID: <20200129151243.GA488@jagdpanzerIV.localdomain> References: <20200127114719.69114-1-andriy.shevchenko@linux.intel.com> <20200127114719.69114-5-andriy.shevchenko@linux.intel.com> <20200128051711.GB115889@google.com> <20200128094418.GY32742@smile.fi.intel.com> <20200129134141.GA537@jagdpanzerIV.localdomain> <20200129142558.GF32742@smile.fi.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200129142558.GF32742@smile.fi.intel.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (20/01/29 16:25), Andy Shevchenko wrote: > I understand. Seems the ->setup() has to be idempotent. We can tell the same > for ->exit() in some comment. > > Can you describe, btw, struct console in kernel doc format? > It will be very helpful! We probably need some documentation. > > > In both cases we will get the console to have CON_ENABLED flag set. > > > > And there are sneaky consoles that have CON_ENABLED before we even > > register them. > > So, taking into consideration my comment to the previous patch, what would be > suggested guard here? > > For a starter something like this? > > if ((console->flags & CON_ENABLED) && console->exit) > console->exit(console); This will work if we also add something like this --- diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index a30ff46c0081..01ced6f38776 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -2739,6 +2739,8 @@ void register_console(struct console *newcon) } } + newcon->flags &= ~CON_ENABLED; + if (console_drivers && console_drivers->flags & CON_BOOT) bcon = console_drivers; --- I don't know why some consoles set CON_ENABLED statically. E.g. drivers/tty/serial/mux.c static struct console mux_console = { .name = "ttyB", .write = mux_console_write, .device = uart_console_device, .setup = mux_console_setup, .flags = CON_ENABLED | CON_PRINTBUFFER, .index = 0, .data = &mux_driver, }; No idea... Such consoles still will have CON_ENABLED even if registration failed and we never ->setup() them. -ss