[v2] console: Replace #if 1 with a bool to ignore

Commit Message

Steven Rostedt July 12, 2018, 1:29 p.m. UTC

From: Steven Rostedt (VMware) <[e-mail]>

There's been discussion on the fb list about the addition of
WARN_CONSOLE_UNLOCKED() inside the fb code. The complaint is that when
the fb module is loaded with lockless_register_fb the console lock is
not taken for debugging reasons. With the addition of
WARN_CONSOLE_UNLOCK() within the fb code, this causes the console to
fill up with warnings when trying to debug the fb driver.

There's also a #if 1 that enables the warning which was added before
git history, and we look down on constant #if's in the kernel nowadays
anyway.

Remove the #if 1 and add a ignore_console_lock_warning boolean that can
be set by drivers to ignore the warning in order to do debugging.

Link: http://lkml.kernel.org/r/[e-mail]
Reviewed-by: Hans de Goede <[e-mail]>
Acked-by: Sergey Senozhatsky <[e-mail]>
Signed-off-by: Steven Rostedt (VMware) <[e-mail]>
---
Changes since V1:
 - Added comment to describe ignore_console_unlock_waring variable
 - Abide by 80 character limit

Comments

Steven Rostedt July 12, 2018, 1:30 p.m. UTC | #1

On Thu, 12 Jul 2018 09:29:38 -0400
Steven Rostedt <[e-mail]> wrote:

> From: Steven Rostedt (VMware) <[e-mail]>
> 
> There's been discussion on the fb list about the addition of
> WARN_CONSOLE_UNLOCKED() inside the fb code. The complaint is that when
> the fb module is loaded with lockless_register_fb the console lock is
> not taken for debugging reasons. With the addition of
> WARN_CONSOLE_UNLOCK() within the fb code, this causes the console to
> fill up with warnings when trying to debug the fb driver.
> 
> There's also a #if 1 that enables the warning which was added before
> git history, and we look down on constant #if's in the kernel nowadays
> anyway.
> 
> Remove the #if 1 and add a ignore_console_lock_warning boolean that can
> be set by drivers to ignore the warning in order to do debugging.
> 
> Link: http://lkml.kernel.org/r/[e-mail]
> Reviewed-by: Hans de Goede <[e-mail]>
> Acked-by: Sergey Senozhatsky <[e-mail]>
> Signed-off-by: Steven Rostedt (VMware) <[e-mail]>

Petr,

If you want this to go by way of fbdev tree, then can you Ack it?

-- Steve

> ---
> Changes since V1:
>  - Added comment to describe ignore_console_unlock_waring variable
>  - Abide by 80 character limit
> 
> Index: linux-trace.git/include/linux/console.h
> ===================================================================
> --- linux-trace.git.orig/include/linux/console.h
> +++ linux-trace.git/include/linux/console.h
> @@ -200,11 +200,14 @@ void vcs_make_sysfs(int index);
>  void vcs_remove_sysfs(int index);
>  
>  /* Some debug stub to catch some of the obvious races in the VT code */
> -#if 1
> -#define WARN_CONSOLE_UNLOCKED()	WARN_ON(!is_console_locked() && !oops_in_progress)
> -#else
> -#define WARN_CONSOLE_UNLOCKED()
> -#endif
> +#define WARN_CONSOLE_UNLOCKED()						\
> +	WARN_ON(!ignore_console_lock_warning &&				\
> +		!is_console_locked() && !oops_in_progress)
> +/*
> + * Set ignore_console_lock_warning to true if you need to quiet
> + * WARN_CONSOLE_UNLOCKED() for debugging purposes.
> + */
> +extern bool ignore_console_lock_warning;
>  
>  /* VESA Blanking Levels */
>  #define VESA_NO_BLANKING        0
> Index: linux-trace.git/kernel/printk/printk.c
> ===================================================================
> --- linux-trace.git.orig/kernel/printk/printk.c
> +++ linux-trace.git/kernel/printk/printk.c
> @@ -66,6 +66,9 @@ int console_printk[4] = {
>  	CONSOLE_LOGLEVEL_DEFAULT,	/* default_console_loglevel */
>  };
>  
> +bool ignore_console_lock_warning __read_mostly;
> +EXPORT_SYMBOL(ignore_console_lock_warning);
> +
>  /*
>   * Low level drivers may need that to know if they can schedule in
>   * their unblank() callback or not. So let's export it.

Petr Mladek July 12, 2018, 1:43 p.m. UTC | #2

On Thu 2018-07-12 09:30:49, Steven Rostedt wrote:
> On Thu, 12 Jul 2018 09:29:38 -0400
> Steven Rostedt <[e-mail]> wrote:
> 
> > From: Steven Rostedt (VMware) <[e-mail]>
> > 
> > There's been discussion on the fb list about the addition of
> > WARN_CONSOLE_UNLOCKED() inside the fb code. The complaint is that when
> > the fb module is loaded with lockless_register_fb the console lock is
> > not taken for debugging reasons. With the addition of
> > WARN_CONSOLE_UNLOCK() within the fb code, this causes the console to
> > fill up with warnings when trying to debug the fb driver.
> > 
> > There's also a #if 1 that enables the warning which was added before
> > git history, and we look down on constant #if's in the kernel nowadays
> > anyway.
> > 
> > Remove the #if 1 and add a ignore_console_lock_warning boolean that can
> > be set by drivers to ignore the warning in order to do debugging.
> > 
> > Link: http://lkml.kernel.org/r/[e-mail]
> > Reviewed-by: Hans de Goede <[e-mail]>
> > Acked-by: Sergey Senozhatsky <[e-mail]>
> > Signed-off-by: Steven Rostedt (VMware) <[e-mail]>
> 
> Petr,
> 
> If you want this to go by way of fbdev tree, then can you Ack it?

Sure.

Acked-by: Petr Mladek <[e-mail]>

I assume that it will go via fbdev tree with the other changes
unless I hear otherwise.

Best Regards,
Petr

Thomas Zimmermann July 18, 2018, 8:15 a.m. UTC | #3

Am 12.07.2018 um 15:29 schrieb Steven Rostedt:
> 
> From: Steven Rostedt (VMware) <[e-mail]>
> 
> There's been discussion on the fb list about the addition of
> WARN_CONSOLE_UNLOCKED() inside the fb code. The complaint is that when
> the fb module is loaded with lockless_register_fb the console lock is
> not taken for debugging reasons. With the addition of
> WARN_CONSOLE_UNLOCK() within the fb code, this causes the console to
> fill up with warnings when trying to debug the fb driver.
> 
> There's also a #if 1 that enables the warning which was added before
> git history, and we look down on constant #if's in the kernel nowadays
> anyway.
> 
> Remove the #if 1 and add a ignore_console_lock_warning boolean that can
> be set by drivers to ignore the warning in order to do debugging.
> 
> Link: http://lkml.kernel.org/r/[e-mail]
> Reviewed-by: Hans de Goede <[e-mail]>
> Acked-by: Sergey Senozhatsky <[e-mail]>
> Signed-off-by: Steven Rostedt (VMware) <[e-mail]>
> ---
> Changes since V1:
>  - Added comment to describe ignore_console_unlock_waring variable
>  - Abide by 80 character limit
> 
> Index: linux-trace.git/include/linux/console.h
> ===================================================================
> --- linux-trace.git.orig/include/linux/console.h
> +++ linux-trace.git/include/linux/console.h
> @@ -200,11 +200,14 @@ void vcs_make_sysfs(int index);
>  void vcs_remove_sysfs(int index);
>  
>  /* Some debug stub to catch some of the obvious races in the VT code */
> -#if 1
> -#define WARN_CONSOLE_UNLOCKED()	WARN_ON(!is_console_locked() && !oops_in_progress)
> -#else
> -#define WARN_CONSOLE_UNLOCKED()
> -#endif
> +#define WARN_CONSOLE_UNLOCKED()						\
> +	WARN_ON(!ignore_console_lock_warning &&				\
> +		!is_console_locked() && !oops_in_progress)
> +/*
> + * Set ignore_console_lock_warning to true if you need to quiet
> + * WARN_CONSOLE_UNLOCKED() for debugging purposes.
> + */
> +extern bool ignore_console_lock_warning;
>  
>  /* VESA Blanking Levels */
>  #define VESA_NO_BLANKING        0
> Index: linux-trace.git/kernel/printk/printk.c
> ===================================================================
> --- linux-trace.git.orig/kernel/printk/printk.c
> +++ linux-trace.git/kernel/printk/printk.c
> @@ -66,6 +66,9 @@ int console_printk[4] = {
>  	CONSOLE_LOGLEVEL_DEFAULT,	/* default_console_loglevel */
>  };
>  
> +bool ignore_console_lock_warning __read_mostly;
> +EXPORT_SYMBOL(ignore_console_lock_warning);
> +
>  /*
>   * Low level drivers may need that to know if they can schedule in
>   * their unblank() callback or not. So let's export it.
> _______________________________________________
> dri-devel mailing list
> [e-mail]
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 

This resolves the problem for me.

Tested-by: Thomas Zimmermann <[e-mail]>

Bartlomiej Zolnierkiewicz July 24, 2018, 4:13 p.m. UTC | #4

On Thursday, July 12, 2018 09:29:38 AM Steven Rostedt wrote:
> 
> From: Steven Rostedt (VMware) <[e-mail]>
> 
> There's been discussion on the fb list about the addition of
> WARN_CONSOLE_UNLOCKED() inside the fb code. The complaint is that when
> the fb module is loaded with lockless_register_fb the console lock is
> not taken for debugging reasons. With the addition of
> WARN_CONSOLE_UNLOCK() within the fb code, this causes the console to
> fill up with warnings when trying to debug the fb driver.
> 
> There's also a #if 1 that enables the warning which was added before
> git history, and we look down on constant #if's in the kernel nowadays
> anyway.
> 
> Remove the #if 1 and add a ignore_console_lock_warning boolean that can
> be set by drivers to ignore the warning in order to do debugging.
> 
> Link: http://lkml.kernel.org/r/[e-mail]
> Reviewed-by: Hans de Goede <[e-mail]>
> Acked-by: Sergey Senozhatsky <[e-mail]>
> Signed-off-by: Steven Rostedt (VMware) <[e-mail]>

Patch queued for 4.19, thanks.

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics

Bartlomiej Zolnierkiewicz July 24, 2018, 4:18 p.m. UTC | #5

On Tuesday, July 24, 2018 06:13:19 PM Bartlomiej Zolnierkiewicz wrote:
> On Thursday, July 12, 2018 09:29:38 AM Steven Rostedt wrote:
> > 
> > From: Steven Rostedt (VMware) <[e-mail]>
> > 
> > There's been discussion on the fb list about the addition of
> > WARN_CONSOLE_UNLOCKED() inside the fb code. The complaint is that when
> > the fb module is loaded with lockless_register_fb the console lock is
> > not taken for debugging reasons. With the addition of
> > WARN_CONSOLE_UNLOCK() within the fb code, this causes the console to
> > fill up with warnings when trying to debug the fb driver.
> > 
> > There's also a #if 1 that enables the warning which was added before
> > git history, and we look down on constant #if's in the kernel nowadays
> > anyway.
> > 
> > Remove the #if 1 and add a ignore_console_lock_warning boolean that can
> > be set by drivers to ignore the warning in order to do debugging.
> > 
> > Link: http://lkml.kernel.org/r/[e-mail]
> > Reviewed-by: Hans de Goede <[e-mail]>
> > Acked-by: Sergey Senozhatsky <[e-mail]>
> > Signed-off-by: Steven Rostedt (VMware) <[e-mail]>
> 
> Patch queued for 4.19, thanks.

Dequeued, I've just noticed a newer patch from Thomas for this issue
(I plan to apply it later this week).

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics

Patch

Index: linux-trace.git/include/linux/console.h
===================================================================
--- linux-trace.git.orig/include/linux/console.h
+++ linux-trace.git/include/linux/console.h
@@ -200,11 +200,14 @@  void vcs_make_sysfs(int index);
 void vcs_remove_sysfs(int index);
 
 /* Some debug stub to catch some of the obvious races in the VT code */
-#if 1
-#define WARN_CONSOLE_UNLOCKED()	WARN_ON(!is_console_locked() && !oops_in_progress)
-#else
-#define WARN_CONSOLE_UNLOCKED()
-#endif
+#define WARN_CONSOLE_UNLOCKED()						\
+	WARN_ON(!ignore_console_lock_warning &&				\
+		!is_console_locked() && !oops_in_progress)
+/*
+ * Set ignore_console_lock_warning to true if you need to quiet
+ * WARN_CONSOLE_UNLOCKED() for debugging purposes.
+ */
+extern bool ignore_console_lock_warning;
 
 /* VESA Blanking Levels */
 #define VESA_NO_BLANKING        0
Index: linux-trace.git/kernel/printk/printk.c
===================================================================
--- linux-trace.git.orig/kernel/printk/printk.c
+++ linux-trace.git/kernel/printk/printk.c
@@ -66,6 +66,9 @@  int console_printk[4] = {
 	CONSOLE_LOGLEVEL_DEFAULT,	/* default_console_loglevel */
 };
 
+bool ignore_console_lock_warning __read_mostly;
+EXPORT_SYMBOL(ignore_console_lock_warning);
+
 /*
  * Low level drivers may need that to know if they can schedule in
  * their unblank() callback or not. So let's export it.