runtime: freebsd/amd64 runtime crashes with heavy threading

[gopherbot]

by thomas.e.zander:

What steps will reproduce the problem?
1. See http://play.golang.org/p/XMTOGXKuIR
2. Execute the program locally (you need /bin/ls and a file system tree)
3. Program crashes in >90% of all cases
4. If you hit one of the cases in which it did not crash, jump to 3.

What is the expected output?
No output, just exiting with return code 0 at some point.

What do you see instead?
All kinds of runtime panics, stack traces etc, for instance the attached one.


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


Which operating system are you using?
FreeBSD-10 amd64

Which version are you using?  (run 'go version')
go version go1.2 freebsd/amd64

Please provide any additional information below.
Problem seems to be triggered by setting runtime.GOMAXPROCS. Commenting out the line in
given example program makes it run stable.

Attachments:

1. errlog.txt (23862 bytes)

[ianlancetaylor]

Comment 1:

Labels changed: added repo-main, release-go1.3.

[davecheney]

Comment 2:

I think there are two issues here.
The first is unrelated to freebsd. It is a misunderstanding of what is happening when
GOMAXPROCS is raised.
In the default configuration the draining of the work queue, ie the number of goroutines
to execute the command is interleaved with the addition of work to the queue.
When GOMAXPROCS is raised the main function can continue to add work to the queue, ie
spawn more goroutines without the scheduling stopping to drain the work to be done.
I do not think this is a bug.
The second part, the crash on freebsd is an issue. I cannot reproduce the problem on
linux, my system runs out of file descriptors.

Status changed to Accepted.

[rsc]

Comment 5:

If someone wants to find the FreeBSD bug, great. But it's not a release blocker for us.

Labels changed: added release-none, suggested, removed release-go1.3.

[gopherbot]

Comment 6 by thomas.e.zander:

I can no longer reproduce this problem in recent FreeBSD builds. Apparently the issue
has been fixed.
This bug can probably be closed after verifying.

[ianlancetaylor]

Comment 7:

Reopen if not fixed.

Status changed to Fixed.