Re: [PATCH v2 05/11] object-store: allow threaded access to object reading

> > However, re-inspecting the code, it seemed to me that we might already
> > have a thread-safe mechanism. The window disposal operations (at
> > close_pack_windows() and unuse_one_window()) are only performed if
> > window.inuse_cnt == 0. So as a thread which reads from the window will
> > also previously increment its inuse_cnt, wouldn't the reading
> > operation be already protected?
> >
> > Another concern would be close_pack_fd(), which can close packs even
> > with in-use windows. However, as the mmap docs[1] says: "closing the
> > file descriptor does not unmap the region".
> >
> > Finally, we also considered reprepare_packed_git() as a possible
> > conflicting operation. But the function called by it to handle
> > packfile opening, prepare_pack(), won't reopen already available
> > packs. Therefore, IIUC, it will leave the opened windows intact.
> >
> > So, aren't perhaps the window readings performed outside the
> > obj_read_mutex critical section already thread-safe?
>
> Any thoughts on this?