Re: [PATCH 2/2] printk: fix double printing with earlycon

[Steven Rostedt]

On Wed,  1 Mar 2017 19:13:46 +0300
Aleksey Makarov  wrote:

> 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,0x87e02400,115200 -- 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 
> ---
>  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;
>  

We could use a comment right about here, explaining why the below is
needed.

-- Steve

> + 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

Re: [PATCH 2/2] printk: fix double printing with earlycon

[Steven Rostedt]

On Wed,  1 Mar 2017 19:13:46 +0300
Aleksey Makarov  wrote:

> 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,0x87e02400,115200 -- 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 
> ---
>  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;
>  

We could use a comment right about here, explaining why the below is
needed.

-- Steve

> + 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

[PATCH 2/2] printk: fix double printing with earlycon

[Aleksey Makarov]

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,0x87e02400,115200 -- 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 
---
 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

[PATCH 2/2] printk: fix double printing with earlycon

[Aleksey Makarov]

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,0x87e02400,115200 -- 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 
---
 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