🐛 Protect the spacesPerId variable by a barrier

[ferologics]

Fixes Thread 1: EXC_BAD_ACCESS crash that would occur whenever multiple concurrent threads would attempt to mutate spacesPerId at the same time.

Signed-off-by: Frantisek Hetes f.hetes@gmail.com

[stefanceriu]

To me the problem seems to stem from loadData() setting self.graph from the processingQueue, which in turn, through its didSet sets self.spacesPerId.
getSpace() on the other hand would normally set it from the main queue.

Perhaps a simpler solution would be to internally protect getSpace() on the same processingQueue? 🤔

public func getSpace(withId spaceId: String) -> MXSpace? {
        var space: MXSpace?
        processingQueue.sync {
            space = self.spacesPerId[spaceId]
        }
        
        if space == nil, let newSpace = self.session.room(withRoomId: spaceId)?.toSpace() {
            space = newSpace
            processingQueue.sync {
                self.spacesPerId[spaceId] = newSpace
            }
        }
        return space
    }

[ferologics]

@stefanceriu maybe that could do the trick 🤔. I used a separate queue to be 100% certain that the read/write operations are not conflicting. Unfortunately I currently lack the scope to test this alternative solution you propose.

[stefanceriu]

It's okay, now that you explained what you intended, I think yours is nicer. I'm happy to merge it after you make those changes.
We want to have this in the next release candidate happening today so please let me know if you can't get to it in time so that I can handle it.

And thank you for taking the time to fix this 👍

[ferologics]

@stefanceriu pushing the patch shortly.

[ferologics]

@stefanceriu done ✅

[stefanceriu]

Looks great, thank you very much! Will merge as soon as the checks finish 👍