Dmitry Eremin-Solenikov(lumag) replied on github web page:
platform/linux-generic/pktio/netmap.c
line 14
@@ -388,13 +389,22 @@ static int netmap_open(odp_pktio_t id ODP_UNUSED,
pktio_entry_t *pktio_entry,
if (pkt_nm->is_virtual) {
static unsigned mac;
+ uint32_t tid = syscall(SYS_gettid);
+
+ if ((int)tid == -1)
Comment:
@matiaselo yes, so this is fine.
> Matias Elo(matiaselo) wrote:
> syscall() specification still defines -1 as an error return value and we
> should adhere to the spec regardless of the function implementation which may
> change.
>> muvarov wrote
>> .
>>> muvarov wrote
>>> man gettid says that it always passes.
>>>
>>> kernel code is also:
>>> pid_t __task_pid_nr_ns(struct task_struct *task, enum pid_type type,
>>> struct pid_namespace *ns)
>>> {
>>> pid_t nr = 0;
>>>
>>> rcu_read_lock();
>>> if (!ns)
>>> ns = task_active_pid_ns(current);
>>> if (likely(pid_alive(task))) {
>>> if (type != PIDTYPE_PID)
>>> task = task->group_leader;
>>> nr = pid_nr_ns(rcu_dereference(task->pids[type].pid), ns);
>>> }
>>> rcu_read_unlock();
>>>
>>> return nr;
>>> }
>>> EXPORT_SYMBOL(__task_pid_nr_ns);
>>>
>>> I.e. it will return init process tid 0 in worst case. So this check is not
>>> correct and not needed.
>>>
>>> It might be needed additional cast:
>>> uint32_t tid = (uint32_t)syscall(SYS_gettid) because of syscall returns
>>> pid_t.
>>>> muvarov wrote
>>>> @lumag we also use SYS_gettid() in shm and timer. I think that is not
>>>> subject for this PR. Just general clean up.
>>>>> Bill Fischofer(Bill-Fischofer-Linaro) wrote:
>>>>> See
>>>>> [here](https://stackoverflow.com/questions/21279649/getting-error-in-c-program-undefined-reference-to-gettid)
>>>>> for an interesting discussion of why gettid() is not used.
>>>>>> Dmitry Eremin-Solenikov(lumag) wrote:
>>>>>> @matiaselo @muvarov Hmm. I thought that there is already a Glibc
>>>>>> wrapper. I would prefer this as a separate function, but it is of minor
>>>>>> priority then.
>>>>>>> muvarov wrote
>>>>>>> it was copied from netmap source I think. gittid() will generate
>>>>>>> warning due to missing glibc wrapper:
>>>>>>> https://stackoverflow.com/questions/30680550/c-gettid-was-not-declared-in-this-scope
>>>>>>> Maybe something already changed...
>>>>>>>> Matias Elo(matiaselo) wrote:
>>>>>>>> What's the benefit from using gettid()? It seems like the only
>>>>>>>> difference is that gettid() cannot fail.
>>>>>>>>> Dmitry Eremin-Solenikov(lumag) wrote:
>>>>>>>>> Why don't you use `gettid()` function? Then you can check for its
>>>>>>>>> existence in `configure.ac` and provide replacement implementation.
https://github.com/Linaro/odp/pull/237#discussion_r146858117
updated_at 2017-10-25 13:36:15
