dynamic_debug: add support for print stack

In practical problem diagnosis, especially during the boot phase, it is
often desirable to know the call sequence. However, currently, apart from
adding print statements and recompiling the kernel, there seems to be no
good alternative. If dynamic_debug supported printing the call stack, it
would be very helpful for diagnosing issues. This patch add support '+d'
for dump stack.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Ye Bin <[e-mail]>
Cc: Jason Baron <[e-mail]>
Cc: Jim Cromie <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

Documentation/admin-guide/dynamic-debug-howto.rst

···
   f    Include the function name
   s    Include the source file name
   l    Include line number
+  d    Include call trace
 
 For ``print_hex_dump_debug()`` and ``print_hex_dump_bytes()``, only
 the ``p`` flag has meaning, other flags are ignored.
 
-Note the regexp ``^[-+=][fslmpt_]+$`` matches a flags specification.
-To clear all flags at once, use ``=_`` or ``-fslmpt``.
+Note the regexp ``^[-+=][fslmptd_]+$`` matches a flags specification.
+To clear all flags at once, use ``=_`` or ``-fslmptd``.
 
 
 Debug messages during Boot Process

include/linux/dynamic_debug.h

···
 #define _DPRINTK_FLAGS_INCL_LINENO	(1<<3)
 #define _DPRINTK_FLAGS_INCL_TID		(1<<4)
 #define _DPRINTK_FLAGS_INCL_SOURCENAME	(1<<5)
+#define _DPRINTK_FLAGS_INCL_STACK	(1<<6)
 
 #define _DPRINTK_FLAGS_INCL_ANY		\
 	(_DPRINTK_FLAGS_INCL_MODNAME | _DPRINTK_FLAGS_INCL_FUNCNAME |\
 	 _DPRINTK_FLAGS_INCL_LINENO  | _DPRINTK_FLAGS_INCL_TID |\
-	 _DPRINTK_FLAGS_INCL_SOURCENAME)
+	 _DPRINTK_FLAGS_INCL_SOURCENAME | _DPRINTK_FLAGS_INCL_STACK)
 
 #if defined DEBUG
 #define _DPRINTK_FLAGS_DEFAULT _DPRINTK_FLAGS_PRINT
···
 			 const struct ib_device *ibdev,
 			 const char *fmt, ...);
 
+#define __dynamic_dump_stack(desc)				\
+{								\
+	if (desc.flags & _DPRINTK_FLAGS_INCL_STACK)		\
+		dump_stack();					\
+}
+
 #define DEFINE_DYNAMIC_DEBUG_METADATA_CLS(name, cls, fmt)	\
 	static struct _ddebug  __aligned(8)			\
 	__section("__dyndbg") name = {				\
···
  */
 #define __dynamic_func_call_cls(id, cls, fmt, func, ...) do {	\
 	DEFINE_DYNAMIC_DEBUG_METADATA_CLS(id, cls, fmt);	\
-	if (DYNAMIC_DEBUG_BRANCH(id))				\
+	if (DYNAMIC_DEBUG_BRANCH(id)) {				\
 		func(&id, ##__VA_ARGS__);			\
+		__dynamic_dump_stack(id);			\
+	}							\
 } while (0)
 #define __dynamic_func_call(id, fmt, func, ...)				\
 	__dynamic_func_call_cls(id, _DPRINTK_CLASS_DFLT, fmt,		\
···
 
 #define __dynamic_func_call_cls_no_desc(id, cls, fmt, func, ...) do {	\
 	DEFINE_DYNAMIC_DEBUG_METADATA_CLS(id, cls, fmt);		\
-	if (DYNAMIC_DEBUG_BRANCH(id))					\
+	if (DYNAMIC_DEBUG_BRANCH(id)) {					\
 		func(__VA_ARGS__);					\
+		__dynamic_dump_stack(id);				\
+	}								\
 } while (0)
 #define __dynamic_func_call_no_desc(id, fmt, func, ...)			\
 	__dynamic_func_call_cls_no_desc(id, _DPRINTK_CLASS_DFLT,	\

lib/dynamic_debug.c

···
 	{ _DPRINTK_FLAGS_INCL_SOURCENAME, 's' },
 	{ _DPRINTK_FLAGS_INCL_LINENO, 'l' },
 	{ _DPRINTK_FLAGS_INCL_TID, 't' },
+	{ _DPRINTK_FLAGS_INCL_STACK, 'd' },
 	{ _DPRINTK_FLAGS_NONE, '_' },
 };