Add a WARN() macro; this is WARN_ON() + printk arguments

Add a WARN() macro that acts like WARN_ON(), with the added feature that it
takes a printk like argument that is printed as part of the warning message.

[akpm@linux-foundation.org: fix printk arguments]
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: Greg KH <greg@kroah.com>
Cc: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/asm-generic/bug.h

@@ -34,9 +34,14 @@ struct bug_entry {
 #ifndef __WARN
 #ifndef __ASSEMBLY__
 extern void warn_on_slowpath(const char *file, const int line);
+extern void warn_slowpath(const char *file, const int line,
+		const char *fmt, ...) __attribute__((format(printf, 3, 4)));
 #define WANT_WARN_ON_SLOWPATH
 #endif
 #define __WARN() warn_on_slowpath(__FILE__, __LINE__)
+#define __WARN_printf(arg...) warn_slowpath(__FILE__, __LINE__, arg)
+#else
+#define __WARN_printf(arg...) __WARN()
 #endif
 
 #ifndef WARN_ON
@@ -48,6 +53,15 @@ extern void warn_on_slowpath(const char *file, const int line);
 })
 #endif
 
+#ifndef WARN
+#define WARN(condition, format...) ({						\
+	int __ret_warn_on = !!(condition);				\
+	if (unlikely(__ret_warn_on))					\
+		__WARN_printf(format);					\
+	unlikely(__ret_warn_on);					\
+})
+#endif
+
 #else /* !CONFIG_BUG */
 #ifndef HAVE_ARCH_BUG
 #define BUG()
@@ -63,6 +77,14 @@ extern void warn_on_slowpath(const char *file, const int line);
 	unlikely(__ret_warn_on);					\
 })
 #endif
+
+#ifndef WARN
+#define WARN(condition, format...) ({					\
+	int __ret_warn_on = !!(condition);				\
+	unlikely(__ret_warn_on);					\
+})
+#endif
+
 #endif
 
 #define WARN_ON_ONCE(condition)	({				\

kernel/panic.c

@@ -318,6 +318,28 @@ void warn_on_slowpath(const char *file, int line)
 	add_taint(TAINT_WARN);
 }
 EXPORT_SYMBOL(warn_on_slowpath);
+
+
+void warn_slowpath(const char *file, int line, const char *fmt, ...)
+{
+	va_list args;
+	char function[KSYM_SYMBOL_LEN];
+	unsigned long caller = (unsigned long)__builtin_return_address(0);
+	sprint_symbol(function, caller);
+
+	printk(KERN_WARNING "------------[ cut here ]------------\n");
+	printk(KERN_WARNING "WARNING: at %s:%d %s()\n", file,
+		line, function);
+	va_start(args, fmt);
+	vprintk(fmt, args);
+	va_end(args);
+
+	print_modules();
+	dump_stack();
+	print_oops_end_marker();
+	add_taint(TAINT_WARN);
+}
+EXPORT_SYMBOL(warn_slowpath);
 #endif
 
 #ifdef CONFIG_CC_STACKPROTECTOR