> > > + * 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) {
> (Apologies for not thinking through all my comments earlier)
> I am wondering if the 'while' loop is required for the write lock.
>
> > > + 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);
> This might fail as the lock was taken (either reader or writer). We should
> return from here as it already indicates that the lock is not
> available for the writer to take. Otherwise, there is a possibility that the
> while loop will run for multiple iterations. I would think, from the
> user's expectation, it might not be correct.
Good point - it will also save us extra read in case of failure.
Will change in v2.
Konstantin
>
> In the read_trylock, the while loop should be fine because the write lock
> itself is not held. The failure could be because some other reader
> incremented the counter before we did. i.e. the reader lock itself may be
> available to take in the next iteration.
>
> > > + }
> > > + return 0;
> > > +}
> > > +
>
