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Code Issues Releases Wiki Activity

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>
This commit is contained in:
Steven Rostedt (VMware) 2017-05-03 11:41:44 -04:00
parent 31805c9052
commit 77c0eddeee
1 changed files with 9 additions and 11 deletions
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20
kernel/trace/ftrace.c
View File

@ -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)