muvarov 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 @lumag yep, I forgot that some syscalls might be not implemented on
some systems, that also will return error.
> Dmitry Eremin-Solenikov(lumag) wrote:
> @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_r147060031
updated_at 2017-10-26 07:09:00
