From: "Steven Rostedt (VMware)" <[email protected]> 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 <[email protected]> Signed-off-by: Steven Rostedt (VMware) <[email protected]> --- kernel/trace/ftrace.c | 20 +++++++++----------- 1 file changed, 9 insertions(+), 11 deletions(-) diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 84286d347cd8..39dca4e86a94 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -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) -- 2.10.2
