Question about fence(SC) & Promise about cs431 HOT 3 CLOSED

From the Promising semantic paper,

When a thread T executes an SC fence, in addition to the effect of both an acquire and a release fence, T increases both its cur view and the global timemap to the maximum of the two.

In order to avoid cases where execution gets stuck, we must ensure that some message can be read for every location. Thus we require that the view attached to a promise message includes only timestamps of messages that exist in memory at the time the promise is made. [...] Hence, release fences effectively serve also as barriers for promises. We find it convenient to explicitly require this in our semantics: whenever a release fence is performed, the set of promises of the executing thread must be empty.

So T1 can't promise x=1 across the fence in the first place. But I'm not sure how allowing such a promise in this particular case can make the execution get stuck.

from cs431.

• Thanks, @tomtomjhj !
• I'll give a thought, either.

from cs431.

@tomtomjhj Thanks for a thoughtful answer.

from cs431.