[dpdk-dev] [PATCH 1/2] rwlock: introduce 'try' semantics for RD and WR locking
Gavin Hu (Arm Technology China)
Gavin.Hu at arm.com
Wed Dec 19 09:30:32 CET 2018
> -----Original Message-----
> From: Honnappa Nagarahalli <Honnappa.Nagarahalli at arm.com>
> Sent: Wednesday, December 19, 2018 2:38 PM
> To: Konstantin Ananyev <konstantin.ananyev at intel.com>; dev at dpdk.org
> Cc: nd <nd at arm.com>; Honnappa Nagarahalli
> <Honnappa.Nagarahalli at arm.com>; Gavin Hu (Arm Technology China)
> <Gavin.Hu at arm.com>; nd <nd at arm.com>
> Subject: RE: [dpdk-dev] [PATCH 1/2] rwlock: introduce 'try' semantics for RD
> and WR locking
>
> >
> > This patch targets 19.02 release.
> >
> > Introduce rte_rwlock_read_trylock() and rte_rwlock_write_trylock().
> > Signed-off-by: Konstantin Ananyev <konstantin.ananyev at intel.com>
> > ---
> > .../common/include/generic/rte_rwlock.h | 54 +++++++++++++++++++
> > lib/librte_eal/rte_eal_version.map | 2 +
> > 2 files changed, 56 insertions(+)
> >
> > diff --git a/lib/librte_eal/common/include/generic/rte_rwlock.h
> > b/lib/librte_eal/common/include/generic/rte_rwlock.h
> > index 5751a0e6d..7e395781e 100644
> > --- a/lib/librte_eal/common/include/generic/rte_rwlock.h
> > +++ b/lib/librte_eal/common/include/generic/rte_rwlock.h
> > @@ -75,6 +75,33 @@ rte_rwlock_read_lock(rte_rwlock_t *rwl)
> > }
> > }
> >
> > +/**
> Please add the experimental API warning
>
> > + * try to take a read lock.
> > + *
> > + * @param rwl
> > + * A pointer to a rwlock structure.
> > + * @return
> > + * - zero if the lock is successfully taken
> > + * - -EBUSY if lock could not be acquired for reading because a
> > + * writer holds the lock
> > + */
> > +static inline __rte_experimental int
> > +rte_rwlock_read_trylock(rte_rwlock_t *rwl) {
> > + int32_t x;
> > + int success = 0;
> > +
> > + while (success == 0) {
> > + x = rwl->cnt;
> > + /* write lock is held */
> > + if (x < 0)
> > + return -EBUSY;
> > + success = rte_atomic32_cmpset((volatile uint32_t *)&rwl-
> >cnt,
> > + (uint32_t)x, (uint32_t)(x + 1));
> > + }
> > + return 0;
> > +}
> > +
> > /**
> > * Release a read lock.
> > *
> > @@ -87,6 +114,33 @@ rte_rwlock_read_unlock(rte_rwlock_t *rwl)
> > rte_atomic32_dec((rte_atomic32_t *)(intptr_t)&rwl->cnt); }
> >
> > +/**
> Please add the experimental API warning
>
> > + * try to take a write lock.
> > + *
> > + * @param rwl
> > + * A pointer to a rwlock structure.
> > + * @return
> > + * - zero if the lock is successfully taken
> > + * - -EBUSY if lock could not be acquired for writing because
> > + * it was already locked for reading or writing
> > + */
> > +static inline __rte_experimental int
> > +rte_rwlock_write_trylock(rte_rwlock_t *rwl) {
> > + int32_t x;
> > + int success = 0;
> > +
> > + while (success == 0) {
> > + x = rwl->cnt;
> > + /* a lock is held */
> > + if (x != 0)
> > + return -EBUSY;
> > + success = rte_atomic32_cmpset((volatile uint32_t *)&rwl-
> >cnt,
> > + 0, (uint32_t)-1);
> > + }
> > + return 0;
> > +}
> > +
> > /**
> > * Take a write lock. Loop until the lock is held.
> > *
> > diff --git a/lib/librte_eal/rte_eal_version.map
> > b/lib/librte_eal/rte_eal_version.map
> > index 3fe78260d..8b1593dd8 100644
> > --- a/lib/librte_eal/rte_eal_version.map
> > +++ b/lib/librte_eal/rte_eal_version.map
> > @@ -355,6 +355,8 @@ EXPERIMENTAL {
> > rte_mp_request_async;
> > rte_mp_sendmsg;
> > rte_option_register;
> > + rte_rwlock_read_trylock;
> > + rte_rwlock_write_trylock;
> I do not see the other RW lock APIs in this file.
>
> > rte_service_lcore_attr_get;
> > rte_service_lcore_attr_reset_all;
> > rte_service_may_be_active;
> > --
> > 2.17.1
>
> Other than the minor comments,
> Reviewed-by: Honnappa Nagarahalli <Honnappa.nagarahalli at arm.com>
Same comments as Honnappa, experimental warning is required in new code.
Reviewed-by: Gavin Hu <gavin.hu at arm.com>
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