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[80.240.102.213]) by smtp.gmail.com with ESMTPSA id 67sm2959434ljb.52.2017.03.20.03.07.26 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 20 Mar 2017 03:07:27 -0700 (PDT) From: Aleksey Makarov To: linux-serial@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Aleksey Makarov , Sudeep Holla , Greg Kroah-Hartman , Peter Hurley , Jiri Slaby , Robin Murphy , Steven Rostedt , "Nair, Jayachandran" , Sergey Senozhatsky , Petr Mladek Subject: [PATCH v8 3/3] printk: fix double printing with earlycon Date: Mon, 20 Mar 2017 13:03:00 +0300 Message-Id: <20170320100302.8656-1-aleksey.makarov@linaro.org> X-Mailer: git-send-email 2.12.0 In-Reply-To: <20170315102854.1763-1-aleksey.makarov@linaro.org> References: <20170315102854.1763-1-aleksey.makarov@linaro.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If a console was specified by ACPI SPCR table _and_ command line parameters like "console=ttyAMA0" _and_ "earlycon" were specified, then log messages appear twice. The root cause is that the code traverses the list of specified consoles (the `console_cmdline` array) and stops at the first match. But it may happen that the same console is referred by the elements of this array twice: pl011,mmio,0x87e024000000,115200 -- from SPCR ttyAMA0 -- from command line but in this case `preferred_console` points to the second entry and the flag CON_CONSDEV is not set, so bootconsole is not deregistered. To fix that, introduce an invariant "The last non-braille console is always the preferred one" on the entries of the console_cmdline array. Then traverse it in reverse order to be sure that if the console is preferred then it will be the first matching entry. Reported-by: Sudeep Holla Signed-off-by: Aleksey Makarov --- v7 -> v8: - add an explanation to the comment how console_cmdline can contain entries referring to the same console - move the body of the function introduced in the previous version to cycle - don't panic() (Sergey Senozhatsky). Don't check this condition because the loop condition guarantees that it holds. - use swap() (Sergey Senozhatsky) v6 -> v7: - return back to v5 - leave the check for already registered entries and add a function that maintains the invariant. v5 -> v6: - drop v5 and continue to work on v4: - introduce _braille_is_braille_console(). It helps to split original loop into three parts: 1) search for braille console, 2) check for preferred_console, 3) match other entries so that these three parts do not intersect. - introduce for_each_console_cmdline() macros to traverse console_cmdline (Petr Mladek) kernel/printk/printk.c | 49 ++++++++++++++++++++++++++++++++++++++++++------- 1 file changed, 42 insertions(+), 7 deletions(-) -- 2.12.0 diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index fd752f0c8ef1..462036e7a767 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -1909,8 +1909,28 @@ static int __add_preferred_console(char *name, int idx, char *options, i < MAX_CMDLINECONSOLES && c->name[0]; i++, c++) { if (strcmp(c->name, name) == 0 && c->index == idx) { - if (!brl_options) - preferred_console = i; + int last; + + if (brl_options) + return 0; + + /* + * Maintain an invariant that will help to find if + * the matching console is preferred, see + * register_console(): + * + * The last non-braille console is always + * the preferred one. + */ + for (last = MAX_CMDLINECONSOLES - 1; + last >= 0 && !console_cmdline[last].name[0]; + last--) + ; + + if (i != last) + swap(console_cmdline[i], console_cmdline[last]); + + preferred_console = last; return 0; } } @@ -2457,12 +2477,27 @@ void register_console(struct console *newcon) } /* - * See if this console matches one we selected on - * the command line. + * See if this console matches one we selected on the command line. + * + * There may be several entries in the console_cmdline array matching + * with the same console, one with newcon->match(), another by + * name/index: + * + * pl011,mmio,0x87e024000000,115200 -- added from SPCR + * ttyAMA0 -- added from command line + * + * Traverse the console_cmdline array in reverse order to be + * sure that if this console is preferred then it will be the first + * matching entry. We use the invariant that is maintained in + * __add_preferred_console(). */ - for (i = 0, c = console_cmdline; - i < MAX_CMDLINECONSOLES && c->name[0]; - i++, c++) { + for (i = MAX_CMDLINECONSOLES - 1; i >= 0; i--) { + + if (!console_cmdline[i].name[0]) + continue; + + c = console_cmdline + i; + if (!newcon->match || newcon->match(newcon, c->name, c->index, c->options) != 0) { /* default matching */