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printk: fix double printing with earlycon 

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.
Introduce variable console_cmdline_cnt that keeps the number
of elements of the console_cmdline array (Petr Mladek).  It helps
to get rid of the loop that searches for the end of this array.

Link: http://lkml.kernel.org/r/20170405202006.18234-1-aleksey.makarov@linaro.org
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: Jiri Slaby <jslaby@suse.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: "Nair, Jayachandran" <Jayachandran.Nair@cavium.com>
Cc: linux-serial@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Aleksey Makarov <aleksey.makarov@linaro.org>
Reported-by: Sudeep Holla <sudeep.holla@arm.com>
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
This commit is contained in:
Aleksey Makarov 2017-04-05 23:20:00 +03:00 committed by Petr Mladek
parent ad86ee2b8a
commit cf39bf58af
1 changed files with 36 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

46
kernel/printk/printk.c
View File

@ -266,6 +266,7 @@ static struct console *exclusive_console;
#define MAX_CMDLINECONSOLES 8
static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
static int console_cmdline_cnt;
static int preferred_console = -1;
int console_set_on_cmdline;
@ -1902,12 +1903,25 @@ static int __add_preferred_console(char *name, int idx, char *options,
* See if this tty is not yet registered, and
* if we have a slot free.
*/
for (i = 0, c = console_cmdline;
i < MAX_CMDLINECONSOLES && c->name[0];
i++, c++) {
for (i = 0, c = console_cmdline; i < console_cmdline_cnt; i++, c++) {
if (strcmp(c->name, name) == 0 && c->index == idx) {
if (!brl_options)
preferred_console = i;
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.
*/
if (i != console_cmdline_cnt - 1)
swap(console_cmdline[i],
console_cmdline[console_cmdline_cnt - 1]);
preferred_console = console_cmdline_cnt - 1;
return 0;
}
}
@ -1920,6 +1934,7 @@ static int __add_preferred_console(char *name, int idx, char *options,
braille_set_options(c, brl_options);
c->index = idx;
console_cmdline_cnt++;
return 0;
}
/*
@ -2459,12 +2474,23 @@ 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 = console_cmdline_cnt - 1; i >= 0; i--) {
c = console_cmdline + i;
if (!newcon->match ||
newcon->match(newcon, c->name, c->index, c->options) != 0) {
/* default matching */