[PATCH v4 32/58] dyndbg: refactor *dynamic_emit_prefix to split lookups

[Jim Cromie]

Split dynamic_emit_prefix():

1. keep dynamic_emit_prefix() static inline
   check ANY flags before calling 2

2. __dynamic_emit_prefix()
   prints [TID] or <intr> if +t flag
   check LOOKUP flags before calling 3

3. __dynamic_emit_lookup()
   prints 1+ of: module, function, src-file, line

Notes:

With 3 only called when needed, print the trailing whitespace
unconditionally, and drop the pos_after_tid var.

By doing TID in 2, 3's output is cacheable in principle.

A prefix cache would allow de-duplicating the redundant data in the
_ddebug tables, and replacing them with space-efficient storage which
is not fast enough for every-time pr_debugs, but would work to fill
the cache the 1st time its enabled and invoked.

Signed-off-by: Jim Cromie <jim.cro...@gmail.com>
---
 lib/dynamic_debug.c | 40 +++++++++++++++++++++++++---------------
 1 file changed, 25 insertions(+), 15 deletions(-)

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index c3e27637d9357..26261b5f99f05 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -824,19 +824,8 @@ static int remaining(int wrote)
        return 0;
 }
 
-static char *__dynamic_emit_prefix(const struct _ddebug *desc, char *buf)
+static int __dynamic_emit_lookup(const struct _ddebug *desc, char *buf, int 
pos)
 {
-       int pos_after_tid;
-       int pos = 0;
-
-       if (desc->flags & _DPRINTK_FLAGS_INCL_TID) {
-               if (in_interrupt())
-                       pos += snprintf(buf + pos, remaining(pos), "<intr> ");
-               else
-                       pos += snprintf(buf + pos, remaining(pos), "[%d] ",
-                                       task_pid_vnr(current));
-       }
-       pos_after_tid = pos;
        if (desc->flags & _DPRINTK_FLAGS_INCL_MODNAME)
                pos += snprintf(buf + pos, remaining(pos), "%s:",
                                desc->modname);
@@ -849,8 +838,29 @@ static char *__dynamic_emit_prefix(const struct _ddebug 
*desc, char *buf)
        if (desc->flags & _DPRINTK_FLAGS_INCL_LINENO)
                pos += snprintf(buf + pos, remaining(pos), "%d:",
                                desc->lineno);
-       if (pos - pos_after_tid)
-               pos += snprintf(buf + pos, remaining(pos), " ");
+
+       /* we have a non-empty prefix, add trailing space */
+       if (remaining(pos))
+               buf[pos++] = ' ';
+
+       return pos;
+}
+
+static char *__dynamic_emit_prefix(struct _ddebug *desc, char *buf)
+{
+       int pos = 0;
+
+       if (desc->flags & _DPRINTK_FLAGS_INCL_TID) {
+               if (in_interrupt())
+                       pos += snprintf(buf + pos, remaining(pos), "<intr> ");
+               else
+                       pos += snprintf(buf + pos, remaining(pos), "[%d] ",
+                                       task_pid_vnr(current));
+       }
+
+       if (unlikely(desc->flags & _DPRINTK_FLAGS_INCL_LOOKUP))
+               pos += __dynamic_emit_lookup(desc, buf, pos);
+
        if (pos >= PREFIX_SIZE)
                buf[PREFIX_SIZE - 1] = '\0';
 
@@ -859,7 +869,7 @@ static char *__dynamic_emit_prefix(const struct _ddebug 
*desc, char *buf)
 
 static inline char *dynamic_emit_prefix(struct _ddebug *desc, char *buf)
 {
-       if (unlikely(desc->flags & _DPRINTK_FLAGS_INCL_ANY))
+       if (desc->flags & _DPRINTK_FLAGS_INCL_ANY)
                return __dynamic_emit_prefix(desc, buf);
        return buf;
 }
-- 
2.50.1