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> Async/await allows to write concurrent code with no synchronization Well you still need some sort of synchronization, because an "await" allows arbitrary oth
by mike_hearn 4y ago
> Async/await allows to write concurrent code with no synchronization
Well you still need some sort of synchronization, because an "await" allows arbitrary other actions to occur. If an await is introduced in code you transitively call then you might find that some invariant you were expecting to hold has now changed across a call when it previously didn't. Fundamentally, locks are about making invariants atomic and that's independent of exactly how code is scheduled and when.
- jayd16 4y agoThis is impossible because of *gasp function coloring. You can't just make a sync function async without dealing with the fallout explicitly in c#.
- mike_hearn 4y agoYou can make an async function contain an await at more places than it previously had. When writing code in colored languages your code tends towards lots of stuff being marked async, so more 'await' points being introduced can change behavior.
- jayd16 4y agoYou're saying something is bad because it could affect a race condition you had? Doesn't everything fall under that issue? That's not changing from invariant to variant.
- mike_hearn 4y agoI'm not saying it's bad, I'm saying that you can still have races and thus still need some form of synchronization even when using async/await. Whilst in simple cases you can preserve invariants just by carefully choosing where an await is done, as things get more complex you constantly run the risk that someone will introduce another await somewhere else (and maybe more async marked functions to enable that), without understanding that the 'await' can now run code that violates some invariants. Locks and other such mechanisms let you mark certain code as executing atomically regardless of scheduling.