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net: Listener should return errors to pending Accepts when it is Closed #1898

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adg opened this issue May 30, 2011 · 11 comments
Closed

net: Listener should return errors to pending Accepts when it is Closed #1898

adg opened this issue May 30, 2011 · 11 comments
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@adg
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adg commented May 30, 2011 

For the net.Listener L some goroutines may be blocking on call to L.Accept(). If another
goroutine calls L.Close(), should those other goroutines receive an error?

The code below tests the behavior. Currently the Accept will block forever, and the
message "Shutting down" will never be seen.

--

package main

import (
    "log"
    "net"
    "time"
)

func main() {
    l, err := net.Listen("tcp", "localhost:2000")
    if err != nil {
        log.Fatal(err)
    }
    log.Println("Listening")
    go func() {
        time.Sleep(2e9)
        log.Println("Closing")
        l.Close()
    }()
    _, err = l.Accept()
    log.Println("Shutting down:", err)
}
@kylelemons
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Comment 1:

I solve this by making a dummy Dial() on the listener port and ignoring the error
return.  It's not ideal, but it works.  Returning an error from all active Accepts()
would be a much cleaner solution if it can be done.

@rsc
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rsc commented May 31, 2011

Comment 2:

Yes

@gopherbot
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Comment 4 by grijalva:

I've run into this same issue.  Does anybody have any guidance for where one might start
solving the root problem?  I don't know the innards of the net library very well.

@bradfitz
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Comment 5:

Fix is in progress here:
http://golang.org/cl/4953047/

@bradfitz
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bradfitz commented Nov 7, 2011

Comment 6:

Is this fixed now?
On Linux at least I now get:
2011/11/07 13:37:41 Listening
2011/11/07 13:37:43 Closing
2011/11/07 13:37:43 Shutting down: invalid argument
... but I don't remember seeing the change that fixed this.
Is it guaranteed that the return value in this case is EINVAL?  Should this be
documented / tested somewhere?

@mikioh
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mikioh commented Nov 7, 2011

Comment 7:

> Is this fixed now?
No, at least on darwin and freebsd,
2011/11/08 07:39:26 Listening
2011/11/08 07:39:28 Closing
and if we poke at this service by telnet localhost 2000,
we eventually get:
2011/11/08 07:40:35 Shutting down: invalid argument

@rsc
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rsc commented Dec 9, 2011

Comment 8:

Labels changed: added priority-later, removed priority-medium.

@rsc
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rsc commented Dec 12, 2011

Comment 9:

Labels changed: added priority-go1.

@robpike
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robpike commented Jan 13, 2012

Comment 10:

Owner changed to builder@golang.org.

@rsc
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rsc commented Feb 12, 2012

Comment 12:

Owner changed to @rsc.

Status changed to Started.

@rsc
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rsc commented Feb 14, 2012

Comment 13:

This issue was closed by revision 5e4e3d8.

Status changed to Fixed.

@adg adg added fixed labels Feb 14, 2012
@adg adg assigned rsc Feb 14, 2012
@rsc rsc added this to the Go1 milestone Apr 10, 2015
@rsc rsc removed the priority-go1 label Apr 10, 2015
@golang golang locked and limited conversation to collaborators Jun 24, 2016
@rsc rsc removed their assignment Jun 22, 2022
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@bradfitz @mikioh @rsc @kylelemons @robpike @adg @gopherbot