CODEWITHSUNDEEP
rust
Ashika Umanga Umagiliya
Ashika Umanga Umagiliya

Reputation: 9158

Rust concurrency question with SyncSender

I am new to Rust and trying to understand the Dining Philosopher code here :

https://google.github.io/comprehensive-rust/exercises/day-4/solutions-morning.html

By the time the execution reaches the following lines in the main thread, isn't it possible that none of the spawned threads have started executing their logic, resulting in nothing in 'rx' and the program simply quitting?

for thought in rx {
        println!("{}", thought);
}

Upvotes: 1

Views: 80

Answers (2)

pigeonhands
pigeonhands

Reputation: 3414

When iterating over a channel, it internally calls Receiver::recv, where the documentation specifies

This function will always block the current thread if there is no data available and it’s possible for more data to be sent (at least one sender still exists). Once a message is sent to the corresponding Sender (or SyncSender), this receiver will wake up and return that message.

So the receiver will block until it has data avalible, or all the senders have been dropped.

Upvotes: 3

kmdreko
kmdreko

Reputation: 59902

Yes, execution can reach for thought in rx { ... } before the threads have even started. However, this will still work because iterating over a Receiver will wait until there is a message and will only stop if all Senders have been destroyed (ergo it is no longer possible to receive any messages).

Upvotes: 2

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