Re: [dpdk-dev] [PATCH] eal/rwlocks: Try read/write and relock write to read locks added.

[Thomas Monjalon <thomas@monjalon.net>]

Closing this proposal.

For reference, an implementation with test has been merged
2 years ago:
https://inbox.dpdk.org/dev/1542130061-3702-1-git-send-email-konstantin.ananyev@intel.com/


12/07/2018 15:55, Thomas Monjalon:
> Hi,
> 
> Unfortunately, after 2 months, nobody reviewed this patch.
> 
> You could motivate some reviews by providing some explanations
> or context of use.
> 
> 
> 21/05/2018 11:08, Leonid Myravjev:
> > From: Leonid Myravjev <myravjev@amicon.ru>
> > 
> > Signed-off-by: Leonid Myravjev <myravjev@amicon.ru>
> > ---
> >  lib/librte_eal/common/include/generic/rte_rwlock.h | 61 ++++++++++++++++++++++
> >  1 file changed, 61 insertions(+)
> > 
> > diff --git a/lib/librte_eal/common/include/generic/rte_rwlock.h b/lib/librte_eal/common/include/generic/rte_rwlock.h
> > index 899e9bc43..11212e2b8 100644
> > --- a/lib/librte_eal/common/include/generic/rte_rwlock.h
> > +++ b/lib/librte_eal/common/include/generic/rte_rwlock.h
> > @@ -76,6 +76,30 @@ rte_rwlock_read_lock(rte_rwlock_t *rwl)
> >  }
> >  
> >  /**
> > + * Try take lock a read lock.
> > + *
> > + * @param rwl
> > + *   A pointer to a rwlock structure.
> > + * @return
> > + *   1 if the lock is successfully taken; 0 otherwise.
> > + */
> > +static inline int
> > +rte_rwlock_read_trylock(rte_rwlock_t *rwl)
> > +{
> > +	int32_t x;
> > +	int success = 0;
> > +
> > +	x = rwl->cnt;
> > +	/* write lock is held */
> > +	if (x < 0)
> > +		return 0;
> > +	success = rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt, x, x + 1);
> > +	if (success == 0)
> > +		return 0;
> > +	return 1;
> > +}
> > +
> > +/**
> >   * Release a read lock.
> >   *
> >   * @param rwl
> > @@ -110,6 +134,29 @@ rte_rwlock_write_lock(rte_rwlock_t *rwl)
> >  					      0, -1);
> >  	}
> >  }
> > +/**
> > + * Try take a write lock.
> > + *
> > + * @param rwl
> > + *   A pointer to a rwlock structure.
> > + * @return
> > + *   1 if the lock is successfully taken; 0 otherwise.
> > + */
> > +static inline int
> > +rte_rwlock_write_trylock(rte_rwlock_t *rwl)
> > +{
> > +	int32_t x;
> > +	int success = 0;
> > +
> > +	x = rwl->cnt;
> > +	/* a lock is held */
> > +	if (x != 0)
> > +		return 0;
> > +	success = rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt, 0, -1);
> > +	if (success == 0)
> > +		return 0;
> > +	return 1;
> > +}
> >  
> >  /**
> >   * Release a write lock.
> > @@ -124,6 +171,20 @@ rte_rwlock_write_unlock(rte_rwlock_t *rwl)
> >  }
> >  
> >  /**
> > + * Relock write lock to read
> > + *
> > + * @param rwl
> > + *   A pointer to a rwlock structure.
> > + */
> > +static inline void
> > +rte_rwlock_write_relock_read(rte_rwlock_t *rwl)
> > +{
> > +	rte_atomic32_add((rte_atomic32_t *)(intptr_t)&rwl->cnt, 2);
> > +}