Asynchronous preemption

[Yonatan Gizachew]

Is it possible to stop the asynchronous preemption like:

GODEBUG=asyncpreemptoff=1 go build -o libgotest.so -buildmode=c-shared -compiler=gccgo test.go

I am using gccgo compiler. 

[Kurtis Rader]

Yes, although that will only disable async preemption for the "go build" tool chain. It will not disable it in the binary that is the result. So, no, it won't do what I think you're requesting. The reason this is controlled via the "GODEBUG" env var is because it is meant for debugging. It is not expected that a Go program will need to disable async preemption 100% of the time. If you have a situation that does need to always disable it you should probably open a bug report.

--

Kurtis Rader

Caretaker of the exceptional canines Junior and Hank

[Ian Lance Taylor]

On Wed, Sep 2, 2020 at 7:14 PM Yonatan Gizachew <eme...@gmail.com> wrote:
>

Note that executables built by the gccgo compiler don't use
asynchronous preemption.

Ian

[Yonatan Gizachew]

Ok, thanks for the clarification. 

[Yonatan Gizachew]

I see. If that is so, what is the job of sysmon thread?

[Ian Lance Taylor]

On Wed, Sep 2, 2020 at 9:11 PM Yonatan Gizachew <eme...@gmail.com> wrote:
>
> I see. If that is so, what is the job of sysmon thread?

The sysmon thread is not related to asynchronous preemption. The
sysmon thread does a few different things. One of the things it does
is notice threads that have been stuck in a system call for a while,
and detach them from their P, and start running a new thread
associated with that P. This is scheduler activity, and it permits
additional parallelism in the program, but it's not preemption.

Ian

> On Thursday, September 3, 2020 at 12:35:26 PM UTC+9 Ian Lance Taylor wrote:
>>
>> On Wed, Sep 2, 2020 at 7:14 PM Yonatan Gizachew <eme...@gmail.com> wrote:
>> >
>> > Is it possible to stop the asynchronous preemption like:
>> > GODEBUG=asyncpreemptoff=1 go build -o libgotest.so -buildmode=c-shared -compiler=gccgo test.go
>> >
>> > I am using gccgo compiler.
>>
>> Note that executables built by the gccgo compiler don't use
>> asynchronous preemption.
>>
>> Ian
>

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[Yonatan Gizachew]

Got it. Thank you!