linux-kernel - Re: [PATCH v5 2/3] fbcon: Call WARN_CONSOLE

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Date:   Wed, 11 Jul 2018 11:41:24 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     Daniel Vetter <daniel@...ll.ch>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Petr Mladek <pmladek@...e.com>,
        Linux Fbdev development list <linux-fbdev@...r.kernel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: Re: [PATCH v5 2/3] fbcon: Call WARN_CONSOLE_UNLOCKED() where
 applicable

On Wed, 11 Jul 2018 17:35:10 +0200
Hans de Goede <hdegoede@...hat.com> wrote:

> OK, so if we don't remove it, we should probably make it so that it
> can be used without triggering any WARN_ONs, which would require changing
> the existing WARN_CONSOLE_UNLOCKED() so that the calls from drivers/tty/vt/vt.c
> also do not trigger it ?
> 
> I guess one can just ignore the oopses when debugging, but debugging surely
> would be easier if there are just no oopses ?

What about adding this patch (untested, not even compiled), and then
set it from the fb module.

-- Steve

diff --git a/include/linux/console.h b/include/linux/console.h
index dfd6b0e97855..11cd4956a57f 100644
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -200,8 +200,10 @@ 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 */
+extern bool ignore_console_lock_warning;
 #if 1
-#define WARN_CONSOLE_UNLOCKED()	WARN_ON(!is_console_locked() && !oops_in_progress)
+#define WARN_CONSOLE_UNLOCKED()						\
+	WARN_ON(!ignore_console_lock_warning && !is_console_locked() && !oops_in_progress)
 #else
 #define WARN_CONSOLE_UNLOCKED()
 #endif
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 247808333ba4..fa15d7ddf0c4 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -66,6 +66,9 @@ int console_printk[4] = {
 	CONSOLE_LOGLEVEL_DEFAULT,	/* default_console_loglevel */
 };
 
+bool ignore_console_lock_warning;
+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.