linux-kernel - [PATCH] console: Replace #if 1 with a bool to ignore WARN_CONSOLE

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Date:   Wed, 11 Jul 2018 15:17:55 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH] console: Replace #if 1 with a bool to ignore
 WARN_CONSOLE_UNLOCKED()


From: Steven Rostedt (VMware) <rostedt@...dmis.org>

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/717e6337-e7a6-7a92-1c1b-8929a25696b5@suse.de
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
diff --git a/include/linux/console.h b/include/linux/console.h
index dfd6b0e97855..9d4a6b985154 100644
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -200,11 +200,9 @@ 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
+extern bool ignore_console_lock_warning;
+#define WARN_CONSOLE_UNLOCKED()						\
+	WARN_ON(!ignore_console_lock_warning && !is_console_locked() && !oops_in_progress)
 
 /* VESA Blanking Levels */
 #define VESA_NO_BLANKING        0
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 247808333ba4..d9056efc3739 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 __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.