On Mon, 9 Sep 2019 08:31:59 +0800 Changbin Du <changbin...@gmail.com> wrote:
> Function ftrace_lookup_ip() will check empty hash table. So we don't > need extra check outside. > > Signed-off-by: Changbin Du <changbin...@gmail.com> > > --- > v2: fix incorrect code remove. > --- > kernel/trace/ftrace.c | 9 ++------- > 1 file changed, 2 insertions(+), 7 deletions(-) > > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c > index f9821a3374e9..92aab854d3b1 100644 > --- a/kernel/trace/ftrace.c > +++ b/kernel/trace/ftrace.c > @@ -1463,8 +1463,7 @@ static bool hash_contains_ip(unsigned long ip, > */ > return (ftrace_hash_empty(hash->filter_hash) || > __ftrace_lookup_ip(hash->filter_hash, ip)) && > - (ftrace_hash_empty(hash->notrace_hash) || > - !__ftrace_lookup_ip(hash->notrace_hash, ip)); > + !ftrace_lookup_ip(hash->notrace_hash, ip); I don't care for this part. I've nacked this change in the past. Why? let's compare the changes: return (ftrace_hash_empty(hash->filter_hash) || __ftrace_lookup_ip(hash->filter_hash, ip)) && (ftrace_hash_empty(hash->notrace_hash) || !__ftrace_lookup_ip(hash->notrace_hash, ip)); vs: return (ftrace_hash_empty(hash->filter_hash) || __ftrace_lookup_ip(hash->filter_hash, ip)) && !ftrace_lookup_ip(hash->notrace_hash, ip); The issue I have with this is that it abstracts out the difference between the filter_hash and the notrace_hash. Sometimes open coded works better if it is compared to something that is similar. The current code I see: Return true if (filter_hash is empty or ip exists in filter_hash and notrace_hash is empty or it does not exist in notrace_hash With your update I see: Return true if filter_hash is empty or ip exists in filter_hash and ip does not exist in notrace_hash It makes it not easy to see if what happens if notrace_hash is empty Hmm, come to think of it, perhaps we should change ftrace_lookup_ip() to include what to do on empty. Maybe: bool ftrace_lookup_ip(struct ftrace_hash *hash, unsigned long ip, bool empty_result) { if (ftrace_hash_empty(hash)) return empty_result; return __ftrace_lookup_ip(hash, ip); } Then we can change the above to: return ftrace_lookup_ip(hash->filter_hash, ip, true) && !ftrace_lookup_ip(hash->notrace_hash, ip, false); That would probably work better. Want to send that update? -- Steve > } > > /* > @@ -6036,11 +6035,7 @@ clear_func_from_hash(struct ftrace_init_func > *func, struct ftrace_hash *hash) { > struct ftrace_func_entry *entry; > > - if (ftrace_hash_empty(hash)) > - return; > - > - entry = __ftrace_lookup_ip(hash, func->ip); > - > + entry = ftrace_lookup_ip(hash, func->ip); > /* > * Do not allow this rec to match again. > * Yeah, it may waste some memory, but will be removed