If a console was specified by ACPI SPCR table _and_
command line parameters like "console=ttyAMA0" _and_ "earlycon"
were specified, then log messages appears twice.

The root cause is that the code traverse 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:

        ttyAMA0 -- from command line
        pl011,mmio,0x87e024000000,115200 -- from SPCR

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, match the console against the `console_cmdline` entry
pointed by `preferred_console` instead of the first match.

Signed-off-by: Aleksey Makarov <[email protected]>
---
 kernel/printk/printk.c | 52 ++++++++++++++++++++++++++++++--------------------
 1 file changed, 31 insertions(+), 21 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index ed2a9b31f214..92008ae9db3f 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2380,6 +2380,24 @@ static int __init keep_bootcon_setup(char *str)
 
 early_param("keep_bootcon", keep_bootcon_setup);
 
+static int match_console(struct console *newcon, struct console_cmdline *c)
+{
+       if (!newcon->match ||
+           newcon->match(newcon, c->name, c->index, c->options) != 0) {
+               /* default matching */
+               BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name));
+               if (strcmp(c->name, newcon->name) != 0)
+                       return -ENODEV;
+               if (newcon->index >= 0 &&
+                   newcon->index != c->index)
+                       return -ENODEV;
+               if (newcon->index < 0)
+                       newcon->index = c->index;
+       }
+
+       return 0;
+}
+
 /*
  * The console driver calls this routine during kernel initialization
  * to register the console printing procedure with printk() and to
@@ -2460,37 +2478,29 @@ void register_console(struct console *newcon)
        for (i = 0, c = console_cmdline;
             i < MAX_CMDLINECONSOLES && c->name[0];
             i++, c++) {
-               if (!newcon->match ||
-                   newcon->match(newcon, c->name, c->index, c->options) != 0) {
-                       /* default matching */
-                       BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name));
-                       if (strcmp(c->name, newcon->name) != 0)
-                               continue;
-                       if (newcon->index >= 0 &&
-                           newcon->index != c->index)
-                               continue;
-                       if (newcon->index < 0)
-                               newcon->index = c->index;
+               if (match_console(newcon, c))
+                       continue;
 
-                       if (_braille_register_console(newcon, c))
-                               return;
+               if (_braille_register_console(newcon, c))
+                       return;
 
-                       if (newcon->setup &&
-                           newcon->setup(newcon, c->options) != 0)
-                               break;
-               }
+               if (newcon->setup &&
+                   newcon->setup(newcon, c->options) != 0)
+                       break;
 
                newcon->flags |= CON_ENABLED;
-               if (i == preferred_console) {
-                       newcon->flags |= CON_CONSDEV;
-                       has_preferred = true;
-               }
                break;
        }
 
        if (!(newcon->flags & CON_ENABLED))
                return;
 
+       if (preferred_console >= 0 &&
+           match_console(newcon, console_cmdline + preferred_console) == 0) {
+               newcon->flags |= CON_CONSDEV;
+               has_preferred = true;
+       }
+
        /*
         * If we have a bootconsole, and are switching to a real console,
         * don't print everything out again, since when the boot console, and
-- 
2.11.1

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