Commit 77c0edde authored May 03, 2017 by Steven Rostedt (VMware)

ftrace: Simplify ftrace_match_record() even more



Dan Carpenter sent a patch to remove a check in ftrace_match_record()
because the logic of the code made the check redundant. I looked deeper into
the code, and made the following logic table, with the three variables and
the result of the original code.

modname        mod_matches     exclude_mod         result
-------        -----------     -----------         ------
  0                 0               0              return 0
  0                 0               1              func_match
  0                 1               *             < cannot exist >
  1                 0               0              return 0
  1                 0               1              func_match
  1                 1               0              func_match
  1                 1               1              return 0

Notice that when mod_matches == exclude mod, the result is always to
return 0, and when mod_matches != exclude_mod, then the result is to test
the function. This means we only need test if mod_matches is equal to
exclude_mod.

Cc: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

parent 31805c90

kernel/trace/ftrace.c

+9 −11

Original line number	Diff line number	Diff line
		@@ -3631,22 +3631,20 @@ ftrace_match_record(struct dyn_ftrace rec, struct ftrace_glob func_g,
		/* blank module name to match all modules */
		if (!mod_g->len) {
		/* blank module globbing: modname xor exclude_mod */
		if ((!exclude_mod) != (!modname))
		if (!exclude_mod != !modname)
		goto func_match;
		return 0;
		}

		/* not matching the module */
		if (!modname \|\| !mod_matches) {
		if (exclude_mod)
		goto func_match;
		else
		return 0;
		}

		if (exclude_mod)
		/*
		* exclude_mod is set to trace everything but the given
		* module. If it is set and the module matches, then
		* return 0. If it is not set, and the module doesn't match
		* also return 0. Otherwise, check the function to see if
		* that matches.
		*/
		if (!mod_matches == !exclude_mod)
		return 0;

		func_match:
		/* blank search means to match all funcs in the mod */
		if (!func_g->len)