Re: [PATCH 18/19] index-helper: autorun

> > Well, the way I read the code it is possible that:
> >
> > 1. Git process 1 starts, reading the index
> > 2. Git process 2 starts, poking the index-helper
> > 3. The index-helper updates the .pid file (why not set a bit in the shared
> >    memory?) with a prefix "W"
> > 4. Git process 2 reads the .pid file and waits for the "W" to go away
> >    (what if index-helper is not fast enough to write the "W"?)
> > 5. Git process 1 access the index, happily oblivious that it is being
> >    updated and the data is in an inconsistent state
> 
> No, if process 1 reads the index file, then that file will remain
> consistent/unchanged all the time. index-helper is not allowed to
> touch that file at all.
> 
> The process 2 gets the index content from shm (cached by the index
> helper), verifies that it's good (with the signature at the end of the
> shm). If watchman is used, process 2 can also read the list of
> modified files from another shm, combine it with the in-core index,
> then write it down the normal way. Only then process 1 (or process 3)
> can see the new index content from the file.