Bill Fischofer(Bill-Fischofer-Linaro) replied on github web page:
platform/linux-generic/odp_packet.c
line 51
@@ -1259,7 +1260,15 @@ int odp_packet_input_index(odp_packet_t pkt)
void odp_packet_user_ptr_set(odp_packet_t pkt, const void *ptr)
{
- packet_hdr(pkt)->buf_hdr.user_ptr = ptr;
+ odp_packet_hdr_t *pkt_hdr = packet_hdr(pkt);
+
+ if (odp_unlikely(ptr == NULL)) {
+ pkt_hdr->p.flags.user_ptr_set = 0;
+ return;
+ }
Comment:
OK
> Petri Savolainen(psavol) wrote:
> This a section label for doxygen. We'll never add it to doxygen config or
> define it otherwise. I think it just need to high light that this portion of
> a file intentionally left hiden from doxygen documentation. "Internal" does
> not tell that this is only a doxygen label, it would seem like a
> configuration option or a preprocessor macro.
>> Petri Savolainen(psavol) wrote:
>> This makes the get side work consistently - code path and performance is the
>> same for NULL values. The flag tells if NULL is returned, or pointer value
>> needs to be read. Reading the pointer value may cause cache miss. The flag
>> needs to be read in any case. If flag is zero, we can return NULL right away
>> (no need to wait for cache to bring NULL value from memory).
>>
>> if (flags.user_ptr_set == 0)
>> return NULL;
>>
>> All NULL cases avoid going to the memory:
>> pkt = alloc()
>> user_ptr(); <-- NULL
>> user_ptr_set(pkt, &foo);
>> user_ptr(); <-- != NULL
>> user_ptr_set(pkt, NULL);
>> user_ptr(); <-- NULL
>> user_ptr(); <-- NULL
>> user_ptr(); <-- NULL
>> user_ptr(); <-- NULL
>>> Bill Fischofer(Bill-Fischofer-Linaro) wrote:
>>> This "optimization" is unnecessary. If the user wants to set the user ptr
>>> to `NULL` that's as legitimate a value as any and will be retrieved
>>> normally. All we care about is whether `odp_packet_user_ptr_set()` has been
>>> called. The flag is reset by `odp_packet_reset()`.
>>>> Bill Fischofer(Bill-Fischofer-Linaro) wrote:
>>>> I like using this feature, but `_ODP_HIDE_FROM_DOXYGEN_` seems awkward
>>>> here. Should we just use `_ODP_INTERNAL_` as a standard means of denoting
>>>> internal items that should not appear in doxygen?
https://github.com/Linaro/odp/pull/392#discussion_r162240332
updated_at 2018-01-18 03:14:34
