Re: [PATCH v4 01/24] Documentation: locking: Describe seqlock design and usage

[Ahmed S. Darwish]

On Mon, Jul 20, 2020 at 09:35:51PM -0400, Steven Rostedt wrote:
> On Mon, 20 Jul 2020 17:55:07 +0200
> "Ahmed S. Darwish" <a.darwish@xxxxxxxxxxxxx> wrote:
> > +Read path, three categories:
> > +
> > +1. Normal Sequence readers which never block a writer but they must
> > +   retry if a writer is in progress by detecting change in the sequence
> > +   number.  Writers do not wait for a sequence reader::
> > +
> > +	do {
> > +		seq = read_seqbegin(&foo_seqlock);
> > +
> > +		/* ... [[read-side critical section]] ... */
> > +
> > +	} while (read_seqretry(&foo_seqlock, seq));
> > +
> > +2. Locking readers which will wait if a writer or another locking reader
> > +   is in progress. A locking reader in progress will also block a writer
> > +   from entering its critical section. This read lock is
> > +   exclusive. Unlike rwlock_t, only one locking reader can acquire it::
>
> Nit, but I would mention that this acts similar to a normal spin_lock,
> and even disables preeption (in the non-RT case).

will do.

Thanks,

--
Ahmed S. Darwish
Linutronix GmbH