thread local storage not work

[calvin2021y]

when link the dynamic library by cgo (without purego), thread local storage work fine.

when use purego load the dynamic library, thread local storage return 0 at first visit, then return value before assign from other os thread.

confirm the problem from linux, windows, macOS. (go1.20.5)

[calvin2021y]

This cloud related with bring the https://github.com/timandy/routine from purego test. I will do more to confirm.

turn out not related into this project.

[calvin2021y]

test to trigger this:

package main

import "C"
import (
    "fmt"
    "github.com/ebitengine/purego"
    "runtime"
    "time"
    "unsafe"
)

//go:linkname gopark runtime.gopark
func gopark(unlockf func(uintptr, unsafe.Pointer) bool, lock unsafe.Pointer, reason uint8, traceEv byte, traceskip int)

func main() {

    lib1, err := purego.Dlopen("printTls.dylib", purego.RTLD_NOW|purego.RTLD_GLOBAL)
    if err != nil {
        panic(err)
    }
    var printTls func(v1 uintptr, d uint32)
    purego.RegisterLibFunc(&printTls, uintptr(lib1), "printTls")

    go func() {
        for {
            time.Sleep(10 * time.Millisecond)
            printTls(0, 211)
        }
    }()

    var max uintptr = 1024 * 8
    var show_at uintptr = 211

    var i uintptr
    for i = 0; i < max; i++ {
        go func(i uintptr) {
            if i%show_at == 0 {
                fmt.Printf("inside %v\n", i)
            }
            gopark(nil, nil, 0, 0, 1)
        }(i)
    }

    time.Sleep(1000 * time.Millisecond)
}

printTls just some simple code to use tls and print it.

If remove fmt.Printf("inside %v\n", i), then the bug not triggered.

If reduce max number it also work, so could be some kind stack overflow.

TLS show wrong var some time correct some time not.

[hajimehoshi]

I think you need to use runtime.LockOSThread to use TLS correctly on a groutine.

[calvin2021y]

the tls only used from c and not related into go. to create a object for each os thread. (I am not sure how to free this object yet, maybe some code like on_thread_exit)

I will do more test to confirm

[hajimehoshi]

printTls should be called in an appropriate OS thread, right?

[calvin2021y]

yes.

I will call from a random go thread, which run inside a random go M, it will do it work inside c world.

[calvin2021y]

I guess this should be my code bugs, not related into purego. I will do more test to confirm

[calvin2021y]

should be my code problem