Re: Emacs design and architecture. How about copy-on-write?

[Emanuel Berg]

Eli Zaretskii wrote:

> it just means any such changes need to be communicated to
> other "redisplaying" threads, so that they also restart

Instead of focusing on specific cases that one can imagine to
be problematic, why not look for a general policy what
should happen in the first place?

So, what does it mean for a thread to lock a global variable?
and set it? and use it? and then unlock it?

What does it mean to that thread for the duration of its
execution? And what does it mean to another thread that is, or
isn't, doing or wanting to do the same thing,
possibly simultaneously?

After that, one can think of how to setup a mechanism that
will safely uphold the model.

So first thing, define what a thread T can do to a global
variable V.

Second thing, what do we want to happen, when another
thread K does the same things in parallel, also to V?

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