Hi, The point is that it cannot be reviewed as stand alone, since reviwer does not see the reason why it's needed. Other two schedulers do not need it, since those do not call dequeue simultaneously from multiple threads for the same queue.
-Petri From: Yi He [mailto:yi...@linaro.org] Sent: Thursday, December 08, 2016 9:40 AM To: Savolainen, Petri (Nokia - FI/Espoo) <petri.savolai...@nokia-bell-labs.com> Cc: lng-odp@lists.linaro.org; bill.fischo...@linaro.org; Elo, Matias (Nokia - FI/Espoo) <matias....@nokia-bell-labs.com> Subject: Re: [lng-odp] [API-NEXT PATCH] linux-gen: scheduler: solve ordered context inversion Hi, Petri I think this patch can stand alone for the problem it explains and solves, the two actions (dequeue events and get context sequence) are non-atomic and preemptable. This patch suggest that in queue dequeue operation, to add a sched->save_context() callback in an atomic manner. So lately default scheduler and SP scheduler can also move the context saving code into this call back, what do you think? Best Regards, Yi On 8 December 2016 at 15:29, Savolainen, Petri (Nokia - FI/Espoo) <petri.savolai...@nokia-bell-labs.com> wrote: This patch belongs to the iquery scheduler patch set. Without the rest of the code, it's impossible to tell if this change is needed or correct. -Petri > -----Original Message----- > From: lng-odp [mailto:lng-odp-boun...@lists.linaro.org] On Behalf Of Yi He > Sent: Thursday, December 08, 2016 8:33 AM > To: lng-odp@lists.linaro.org; bill.fischo...@linaro.org; Elo, Matias > (Nokia - FI/Espoo) <matias....@nokia-bell-labs.com> > Subject: [lng-odp] [API-NEXT PATCH] linux-gen: scheduler: solve ordered > context inversion > > For ordered queue, a thread consumes events (dequeue) and > acquires its unique sequential context in two steps, non > atomic and preemptable. > > This leads to potential ordered context inversion in case > the thread consumes prior events acquired subsequent context, > while the thread consumes subsequent events but acquired > prior context. > > This patch insert the ordered context acquisition into > event dequeue operation to make these two steps atomic. > > Signed-off-by: Yi He <yi...@linaro.org> > --- > When I'm rebase iquery scheduler onto Matias' new ordered > queue impl I found this potential ordered context inversion > issue, it didnot happen to the default scheduler but happens > to the iquery scheduler, so after patchset will rely on this > patch. please help review thanks. > > platform/linux-generic/include/odp_schedule_if.h | 3 +++ > platform/linux-generic/odp_queue.c | 3 +++ > platform/linux-generic/odp_schedule.c | 7 ++++++- > platform/linux-generic/odp_schedule_sp.c | 7 ++++++- > 4 files changed, 18 insertions(+), 2 deletions(-) > > diff --git a/platform/linux-generic/include/odp_schedule_if.h > b/platform/linux-generic/include/odp_schedule_if.h > index 6c2b050..c0aee42 100644 > --- a/platform/linux-generic/include/odp_schedule_if.h > +++ b/platform/linux-generic/include/odp_schedule_if.h > @@ -12,6 +12,7 @@ extern "C" { > #endif > > #include <odp/api/queue.h> > +#include <odp_queue_internal.h> > #include <odp/api/schedule.h> > > typedef void (*schedule_pktio_start_fn_t)(int pktio_index, int > num_in_queue, > @@ -33,6 +34,7 @@ typedef int (*schedule_term_local_fn_t)(void); > typedef void (*schedule_order_lock_fn_t)(void); > typedef void (*schedule_order_unlock_fn_t)(void); > typedef unsigned (*schedule_max_ordered_locks_fn_t)(void); > +typedef void (*schedule_save_context_fn_t)(queue_entry_t *queue); > > typedef struct schedule_fn_t { > schedule_pktio_start_fn_t pktio_start; > @@ -50,6 +52,7 @@ typedef struct schedule_fn_t { > schedule_order_lock_fn_t order_lock; > schedule_order_unlock_fn_t order_unlock; > schedule_max_ordered_locks_fn_t max_ordered_locks; > + schedule_save_context_fn_t save_context; > } schedule_fn_t; > > /* Interface towards the scheduler */ > diff --git a/platform/linux-generic/odp_queue.c b/platform/linux- > generic/odp_queue.c > index d9cb9f3..3b6a68b 100644 > --- a/platform/linux-generic/odp_queue.c > +++ b/platform/linux-generic/odp_queue.c > @@ -568,6 +568,9 @@ static inline int deq_multi(queue_entry_t *queue, > odp_buffer_hdr_t *buf_hdr[], > if (hdr == NULL) > queue->s.tail = NULL; > > + if (queue->s.type == ODP_QUEUE_TYPE_SCHED) > + sched_fn->save_context(queue); > + > UNLOCK(&queue->s.lock); > > return i; > diff --git a/platform/linux-generic/odp_schedule.c b/platform/linux- > generic/odp_schedule.c > index 645630a..264c58f 100644 > --- a/platform/linux-generic/odp_schedule.c > +++ b/platform/linux-generic/odp_schedule.c > @@ -1205,6 +1205,10 @@ static int schedule_num_grps(void) > return NUM_SCHED_GRPS; > } > > +static void schedule_save_context(queue_entry_t *queue ODP_UNUSED) > +{ > +} > + > /* Fill in scheduler interface */ > const schedule_fn_t schedule_default_fn = { > .pktio_start = schedule_pktio_start, > @@ -1221,7 +1225,8 @@ const schedule_fn_t schedule_default_fn = { > .term_local = schedule_term_local, > .order_lock = order_lock, > .order_unlock = order_unlock, > - .max_ordered_locks = schedule_max_ordered_locks > + .max_ordered_locks = schedule_max_ordered_locks, > + .save_context = schedule_save_context > }; > > /* Fill in scheduler API calls */ > diff --git a/platform/linux-generic/odp_schedule_sp.c b/platform/linux- > generic/odp_schedule_sp.c > index 76d1357..8481f29 100644 > --- a/platform/linux-generic/odp_schedule_sp.c > +++ b/platform/linux-generic/odp_schedule_sp.c > @@ -676,6 +676,10 @@ static void order_unlock(void) > { > } > > +static void save_context(queue_entry_t *queue ODP_UNUSED) > +{ > +} > + > /* Fill in scheduler interface */ > const schedule_fn_t schedule_sp_fn = { > .pktio_start = pktio_start, > @@ -692,7 +696,8 @@ const schedule_fn_t schedule_sp_fn = { > .term_local = term_local, > .order_lock = order_lock, > .order_unlock = order_unlock, > - .max_ordered_locks = max_ordered_locks > + .max_ordered_locks = max_ordered_locks, > + .save_context = save_context > }; > > /* Fill in scheduler API calls */ > -- > 2.7.4
