Hi Honnappa,
On Wed, Nov 04, 2020 at 05:57:19PM +0000, Honnappa Nagarahalli wrote:
> <snip>
>
> >
> > Each core already comes with its local storage for mcslock (in its stack),
> > therefore there is no need to define an additional per-lcore mcslock.
> >
> > Fixes: 32dcb9fd2a22 ("test/mcslock: add MCS queued lock unit test")
> >
> > Signed-off-by: Olivier Matz <olivier.m...@6wind.com>
> > ---
> > app/test/test_mcslock.c | 16 ++++++----------
> > 1 file changed, 6 insertions(+), 10 deletions(-)
> >
> > diff --git a/app/test/test_mcslock.c b/app/test/test_mcslock.c index
> > fbca78707d..80eaecc90a 100644
> > --- a/app/test/test_mcslock.c
> > +++ b/app/test/test_mcslock.c
> > @@ -37,10 +37,6 @@
> > * lock multiple times.
> > */
> >
> > -RTE_DEFINE_PER_LCORE(rte_mcslock_t, _ml_me); -
> > RTE_DEFINE_PER_LCORE(rte_mcslock_t, _ml_try_me); -
> > RTE_DEFINE_PER_LCORE(rte_mcslock_t, _ml_perf_me);
> > -
> > rte_mcslock_t *p_ml;
> > rte_mcslock_t *p_ml_try;
> > rte_mcslock_t *p_ml_perf;
> > @@ -53,7 +49,7 @@ static int
> > test_mcslock_per_core(__rte_unused void *arg) {
> > /* Per core me node. */
> > - rte_mcslock_t ml_me = RTE_PER_LCORE(_ml_me);
> > + rte_mcslock_t ml_me;
> These variables are modified by other threads. IMO, it is better to keep them
> global (and not on the stack). From that perspective, I think we should be
> taking the address of the per lcore variable. For ex:
> rte_mcslock_t *ml_me = &RTE_PER_LCORE(_ml_me);
In my understanding, the only case where another thread modifies our
local variable is when the other thread releases the lock we are waiting
for. I can't see how it could cause an issue to have the locks in the
stack. Am I missing something?
Thanks,
Olivier
>
> >
> > rte_mcslock_lock(&p_ml, &ml_me);
> > printf("MCS lock taken on core %u\n", rte_lcore_id()); @@ -77,7
> > +73,7 @@ load_loop_fn(void *func_param)
> > const unsigned int lcore = rte_lcore_id();
> >
> > /**< Per core me node. */
> > - rte_mcslock_t ml_perf_me = RTE_PER_LCORE(_ml_perf_me);
> > + rte_mcslock_t ml_perf_me;
> >
> > /* wait synchro */
> > while (rte_atomic32_read(&synchro) == 0) @@ -151,8 +147,8 @@
> > static int test_mcslock_try(__rte_unused void *arg) {
> > /**< Per core me node. */
> > - rte_mcslock_t ml_me = RTE_PER_LCORE(_ml_me);
> > - rte_mcslock_t ml_try_me = RTE_PER_LCORE(_ml_try_me);
> > + rte_mcslock_t ml_me;
> > + rte_mcslock_t ml_try_me;
> >
> > /* Locked ml_try in the main lcore, so it should fail
> > * when trying to lock it in the worker lcore.
> > @@ -178,8 +174,8 @@ test_mcslock(void)
> > int i;
> >
> > /* Define per core me node. */
> > - rte_mcslock_t ml_me = RTE_PER_LCORE(_ml_me);
> > - rte_mcslock_t ml_try_me = RTE_PER_LCORE(_ml_try_me);
> > + rte_mcslock_t ml_me;
> > + rte_mcslock_t ml_try_me;
> >
> > /*
> > * Test mcs lock & unlock on each core
> > --
> > 2.25.1
>
