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runtime: function referenced by a function is not GC'd #5493

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neild opened this issue May 17, 2013 · 15 comments
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runtime: function referenced by a function is not GC'd #5493

neild opened this issue May 17, 2013 · 15 comments
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Go1.1.1

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@neild
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neild commented May 17, 2013 

What steps will reproduce the problem?
If possible, include a link to a program on play.golang.org.
1. http://play.golang.org/p/6GSIeo4oKF

What is the expected output?
0: finalize invoke
0: finalize f
1: finalize invoke
1: finalize f
...

What do you see instead?
0: finalize invoke
1: finalize invoke
...

Which compiler are you using (5g, 6g, 8g, gccgo)?
6g

Which operating system are you using?
Linux

Which version are you using?  (run 'go version')
Whichever play.golang.org is using.

Please provide any additional information below.
@neild
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neild commented May 17, 2013

Comment 1:

n.b., commenting out the f() on line 10 results in the expected output.

@neild
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neild commented May 17, 2013

Comment 2:

...and never mind.  The cause of this behavior is the finalizer holding the data live
for longer than normal.  Repeating GC passes results in all the data eventually being
collected.

@remyoudompheng
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Comment 3:

Status changed to Retracted.

@neild
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neild commented May 17, 2013

Comment 4:

All right, I think I was on to something, but reduced my test case too far.  I believe
this demonstrates the issue:
http://play.golang.org/p/-XkxEXbpVh

@dvyukov
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dvyukov commented May 19, 2013

Comment 5:

Owner changed to @dvyukov.

Status changed to Started.

@dvyukov
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dvyukov commented May 19, 2013

Comment 6:

Sent https://golang.org/cl/9557043

@ianlancetaylor
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Comment 7:

Labels changed: added priority-soon, go1.1.1, removed priority-triage.

@dvyukov
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dvyukov commented May 20, 2013

Comment 8:

This issue was closed by revision 1308194.

Status changed to Fixed.

@ianlancetaylor
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Comment 9:

Labels changed: removed go1.1.1.

@davecheney
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Comment 10:

I would like to ask that this issue be considered for inclusion in Go 1.1.1, the fix is
only one line, comes with a test, and appears low risk.

@ianlancetaylor
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Comment 11:

We want to make 1.1.1 an absolutely minimal release with only fixes for critical bugs
with no workaround.  This bug only affects when finalizers are run, and that has never
been guaranteed.

@davecheney
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Comment 12:

Okay, thanks for letting me know.

@neild
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neild commented May 30, 2013

Comment 13:

This bug can result in garbage going uncollected indefinitely.  I've observed tasks with
hundreds of MB of uncollected and uncollectable garbage as a result of it.  Without
offering an opinion on whether that's worthy of inclusion in Go 1.1.1, I would say that
this is more significant than just affecting when finalizers run.

@ianlancetaylor
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Comment 14:

Labels changed: added go1.1.1.

@adg
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adg commented Jun 5, 2013

Comment 15:

This issue was closed by revision 91ebf3762c9d.

@rsc rsc added this to the Go1.1.1 milestone Apr 14, 2015
@rsc rsc removed the go1.1.1 label Apr 14, 2015
adg added a commit that referenced this issue May 11, 2015
@adg
[release-branch.go1.1] runtime: zeroize g->fnstart to not prevent GC …
ff7cb87 
…of the closure

««« CL 9557043 / 2c128d417029
runtime: zeroize g->fnstart to not prevent GC of the closure
Fixes #5493.

R=golang-dev, minux.ma, iant
CC=golang-dev
https://golang.org/cl/9557043
»»»

R=dvyukov, iant, minux.ma, bradfitz, dave
CC=golang-dev
https://golang.org/cl/10031043
@golang golang locked and limited conversation to collaborators Jun 24, 2016
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@davecheney @neild @rsc @remyoudompheng @dvyukov @ianlancetaylor @adg @gopherbot