Function ftrace_lookup_ip() will check empty hash table. So we don't
need extra check outside.
Signed-off-by: Changbin Du <[email protected]>
---
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);
}
/*
@@ -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
--
2.20.1
On Mon, 9 Sep 2019 08:31:59 +0800
Changbin Du <[email protected]> wrote:
> Function ftrace_lookup_ip() will check empty hash table. So we don't
> need extra check outside.
>
> Signed-off-by: Changbin Du <[email protected]>
>
> ---
> 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
On Mon, Sep 09, 2019 at 10:54:24AM -0400, Steven Rostedt wrote:
> On Mon, 9 Sep 2019 08:31:59 +0800
> Changbin Du <[email protected]> wrote:
>
> > Function ftrace_lookup_ip() will check empty hash table. So we don't
> > need extra check outside.
> >
> > Signed-off-by: Changbin Du <[email protected]>
> >
> > ---
> > 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);
> }
>
We must add another similar function since ftrace_lookup_ip() returns a pointer.
bool ftrace_contains_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);
}
But after this, it's a little overkill I think. It is not much simpler than before.
Do you still want this then?
> 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
>
--
Cheers,
Changbin Du
On Mon, Sep 09, 2019 at 10:54:24AM -0400, Steven Rostedt wrote:
> On Mon, 9 Sep 2019 08:31:59 +0800
> Changbin Du <[email protected]> wrote:
>
> > Function ftrace_lookup_ip() will check empty hash table. So we don't
> > need extra check outside.
> >
> > Signed-off-by: Changbin Du <[email protected]>
> >
> > ---
> > 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
>
Yes, I agree with you entirly.
> 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?
>
Yes, let me update it with your idea. Thanks!
> -- 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
>
--
Cheers,
Changbin Du
On Tue, 10 Sep 2019 08:33:23 +0800
Changbin Du <[email protected]> wrote:
> >
> > 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);
> > }
> >
> We must add another similar function since ftrace_lookup_ip() returns a pointer.
>
> bool ftrace_contains_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);
> }
>
> But after this, it's a little overkill I think. It is not much simpler than before.
> Do you still want this then?
>
>
Or...
static struct ftrace_func_entry empty_func_entry;
#define EMPTY_FUNC_ENTRY = &empty_func_entry;
[..]
* @empty_result: return NULL if false or EMPTY_FUNC_ENTRY on true
[..]
* @empty_result should be false, unless this is used for testing if the ip
* exists in the hash, and an empty hash should be considered true.
* This is useful when the empty hash is considered to contain all addresses.
[..]
struct ftrace_func_entry *
ftrace_lookup_ip(struct ftrace_hash *hash, unsigned long ip, bool empty_result)
{
if (ftrace_hash_empty(hash))
return empty_result ? EMPTY_FUNC_ENTRY : NULL;
return __ftrace_lookup_ip(hash, ip);
}
But looking at this more, I'm going back to not touching the code in
this location, because __ftrace_lookup_ip() is static, where as
ftrace_lookup_ip() is not, and this is in a very fast path, and I
rather keep it open coded.
Lets just drop the first hunk of your patch. The second hunk is fine.
-- Steve
On Tue, Sep 10, 2019 at 05:28:04AM -0400, Steven Rostedt wrote:
> On Tue, 10 Sep 2019 08:33:23 +0800
> Changbin Du <[email protected]> wrote:
>
> > >
> > > 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);
> > > }
> > >
> > We must add another similar function since ftrace_lookup_ip() returns a pointer.
> >
> > bool ftrace_contains_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);
> > }
> >
> > But after this, it's a little overkill I think. It is not much simpler than before.
> > Do you still want this then?
> >
> >
>
> Or...
>
> static struct ftrace_func_entry empty_func_entry;
> #define EMPTY_FUNC_ENTRY = &empty_func_entry;
>
> [..]
> * @empty_result: return NULL if false or EMPTY_FUNC_ENTRY on true
> [..]
> * @empty_result should be false, unless this is used for testing if the ip
> * exists in the hash, and an empty hash should be considered true.
> * This is useful when the empty hash is considered to contain all addresses.
> [..]
> struct ftrace_func_entry *
> ftrace_lookup_ip(struct ftrace_hash *hash, unsigned long ip, bool empty_result)
> {
> if (ftrace_hash_empty(hash))
> return empty_result ? EMPTY_FUNC_ENTRY : NULL;
>
> return __ftrace_lookup_ip(hash, ip);
> }
>
> But looking at this more, I'm going back to not touching the code in
> this location, because __ftrace_lookup_ip() is static, where as
> ftrace_lookup_ip() is not, and this is in a very fast path, and I
> rather keep it open coded.
>
> Lets just drop the first hunk of your patch. The second hunk is fine.
>
Sure, I will send a update short later. Thanks for your suggestions.
>
> -- Steve
--
Cheers,
Changbin Du