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From: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>
To: Konstantin Ananyev <konstantin.ananyev@intel.com>, "dev@dpdk.org"
<dev@dpdk.org>
CC: nd <nd@arm.com>, Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>,
"Gavin Hu (Arm Technology China)" <Gavin.Hu@arm.com>, nd <nd@arm.com>
Thread-Topic: [dpdk-dev] [PATCH 1/2] rwlock: introduce 'try' semantics for RD
and WR locking
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Date: Wed, 19 Dec 2018 06:37:37 +0000
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Subject: Re: [dpdk-dev] [PATCH 1/2] rwlock: introduce 'try' semantics for RD
and WR locking
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>=20
> This patch targets 19.02 release.
>=20
> Introduce rte_rwlock_read_trylock() and rte_rwlock_write_trylock().
> Signed-off-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
> ---
> .../common/include/generic/rte_rwlock.h | 54 +++++++++++++++++++
> lib/librte_eal/rte_eal_version.map | 2 +
> 2 files changed, 56 insertions(+)
>=20
> 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)
> }
> }
>=20
> +/**
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 =3D 0;
> +
> + while (success =3D=3D 0) {
> + x =3D rwl->cnt;
> + /* write lock is held */
> + if (x < 0)
> + return -EBUSY;
> + success =3D 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); }
>=20
> +/**
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 =3D 0;
> +
> + while (success =3D=3D 0) {
> + x =3D rwl->cnt;
> + /* a lock is held */
> + if (x !=3D 0)
> + return -EBUSY;
> + success =3D 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@arm.com>