From: Stephen Hemminger <stephen@networkplumber.org>
To: "Morten Brørup" <mb@smartsharesystems.com>
Cc: <dev@dpdk.org>
Subject: Re: [PATCH v2] rwlock: prevent readers from starving writers
Date: Tue, 19 Jul 2022 15:33:41 -0700 [thread overview]
Message-ID: <20220719153341.57bf8ecb@hermes.local> (raw)
In-Reply-To: <98CBD80474FA8B44BF855DF32C47DC35D871D6@smartserver.smartshare.dk>
> > /**
> > @@ -179,7 +226,7 @@ rte_rwlock_write_lock(rte_rwlock_t *rwl)
> > static inline void
> > rte_rwlock_write_unlock(rte_rwlock_t *rwl)
> > {
> > - __atomic_store_n(&rwl->cnt, 0, __ATOMIC_RELEASE);
> > + __atomic_fetch_sub(&rwl->cnt, RTE_RWLOCK_WRITE,
> > __ATOMIC_RELEASE);
>
> Yes. This is correct, regardless if another writer thread is waiting or not. (Reviewed for one writer thread using rte_rwlock_write_lock() and another using rte_rwlock_write_trylock().)
>
Was trying to stick to original logic.
After writer releases want both writer and reader to be able to get in equally.
This provide a measure of fairness (no preference) so writers can't starve readers either.
next prev parent reply other threads:[~2022-07-19 22:33 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-07 20:12 [RFC] " Stephen Hemminger
2022-07-08 19:22 ` Honnappa Nagarahalli
2022-07-08 22:04 ` Morten Brørup
2022-07-09 16:22 ` Stephen Hemminger
2022-07-09 16:25 ` Stephen Hemminger
2022-07-19 20:27 ` [PATCH v2] " Stephen Hemminger
2022-07-19 21:52 ` Morten Brørup
2022-07-19 22:33 ` Stephen Hemminger [this message]
2022-07-20 6:48 ` Morten Brørup
2022-10-03 10:01 ` David Marchand
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