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Add some concepts related to exit(3) #17

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Jan 19, 2023
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Add some concepts related to exit(3) #17

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2b7fb32
Add some concepts related to exit(3)
yamt Dec 15, 2022
ccc5811
Rename thread group to process
yamt Dec 16, 2022
ec8172d
Remove thread_exit for now
yamt Jan 4, 2023
dc1ac30
try to make a sentence less odd
yamt Jan 6, 2023
f74d69d
english improvements
yamt Jan 11, 2023
c732034
english improvement
yamt Jan 11, 2023
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39 changes: 39 additions & 0 deletions README.md
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Expand Up @@ -172,6 +172,45 @@ TID is a 32-bit integer to identify threads created with `wasi_thread_spawn`.
For example, it can be used to indicate the main thread, which doesn't
have a TID in the current version of this proposal.

### Process

* A process is a group of threads.

* The main thread starts with a process which only contains
the main thread.

* Threads created by a thread in a process using `wasi_thread_spawn`
is added to the process.
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is added to the process.
are added to the process.

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done


* When a thread is terminated, it's removed from the process.

### Voluntary thread termination

A thread can terminate itself voluntarily by returning from
`wasi_thread_start`.

### Changes to WASI `proc_exit`

With this proposal, the `proc_exit` function takes extra responsibility
to terminate all threads in the process, not only the calling one.
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How about simply "When proc_exit is called the entire process is terminated, including all running threads". I'm not we need the "takes extra responsibility" wording.

It seems fairly clear from its name that proc_exit would do this, so I don't really see it as "extra responsibility", but maybe thats just my reading of it.

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without wasi-threads, a runtime would simply terminate the calling thread.

when adding wasi-threads support to a runtime, you need to make it terminate other thread too. it would need a significant implementation effort. i feel it's appropriate to call it extra.

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Sure. But don't think that is clear enough to simply say: "When proc_exit is called the entire process is terminated, including all running threads".

(BTW, the way I see it proc_exit brings down the entire process (that is that the proc part means), even without wasi-threads. It just happens that there was only ever one thread previously.)

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maybe. i wanted to somehow emphasize that this is something a runtime needs to implement.


Any of threads in the process can call `proc_exit`.
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Any of threads in the process can call `proc_exit`.
Any of the threads in the process can call `proc_exit`.

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done


### Traps

When a thread caused a trap, it terminates all threads in the process
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s/caused/causes/ ?

How about "When a trap occurs in any thread, the entire process is terminated."?

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s/caused/causes/ ?

probably. i'm not good at english as you may noticed.

How about "When a trap occurs in any thread, the entire process is terminated."?

done.

similarly to `proc_exit`.

### Process exit status

If one or more threads call WASI `proc_exit` or raise a trap,
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Does it include calling it proc_exit from the main thread?

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Yes

one of them is chosen by the runtime to represent the exit status
of the process.
It's non deterministic which one is chosen.

If the process gets empty without involving `proc_exit` or a trap,
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"gets empty" sounds a little odd to me. How about "If the last remaining thread in the process returns from its entry point without trapping or calling proc_exit it is treated as if proc_exit was called with exit code 0".

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it isn't only about the last thread.
eg. if the second last thread terminated itself with a trap and the last thread returned from wasi_thread_start, i still want to make the trap represent the process exit status.

also, i want to avoid mentioning the entry point in this sentence because it can involve another topic: #21

how about:

If all the threads in the process have been terminated without calling 
`proc_exit` or raising a trap, it's treated as if the last thread called 
`proc_exit` with exit code 0.

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Sure thats sounds fine. Perhaps we can define "normal termination" and "early termination" and say "If all the threads in the process terminate normally"?

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Sure thats sounds fine.

done

Perhaps we can define "normal termination" and "early termination" and say "If all the threads in the process terminate normally"?

i feel it confusing as calling exit() is quite normal.

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I think its reasonable to refer to "exit()" as early and/or abnormal termination.

it's treated as if the last thread called `proc_exit` with exit code 0.

#### Design choice: pthreads

One of the goals of this API is to be able to support `pthreads` for C compiled
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