Re: [libgpiod] Thread safety API contract

["Erik Schilling" <erik.schilling@xxxxxxxxxx>]

On Wed Sep 13, 2023 at 3:45 PM CEST, Bartosz Golaszewski wrote:
> On Wed, Sep 13, 2023 at 3:36 PM Erik Schilling
> <erik.schilling@xxxxxxxxxx> wrote:
> >
> > On Wed Sep 13, 2023 at 2:03 PM CEST, Bartosz Golaszewski wrote:
> > > On Wed, Sep 13, 2023 at 11:47 AM Erik Schilling
> > > <erik.schilling@xxxxxxxxxx> wrote:
> > > >
> > > > Hi all!
> > > >
> > > > Currently it looks like libgpiod does not document any kind of thread
> > > > safety gurantee. However, the Python bindings tests
> > >
> > > Indeed, the library is thread-aware but not thread-safe. Just like
> > > what is recommended for low-level system libraries.
> >
> > Just to confirm:
> >
> > I assume this means: thread-aware in the sense that all created objects
> > (chips, line_requests, ...) together may only be used by a single thread
> > at once? So line_requests of a same chip may not be used across threads?
> >
>
> They can be used across threads alright. Thread-aware means: no global
> state in the library, IOW two functions won't get in each other's way
> unless they work on the same object.

Sorry, I did not phrase that question super well. A (hopefully) better
try:

If I create a chip and then open two line_requests from that single
chip. Can I use these two line_requests concurrently on different
threads? Or do both of them (and the chip) have to share a single lock?

My assumption was that everything derived from the same chip instance
must not run concurrently.

- Erik