testing: Add verification that tests and benchmarks do ...

testing: Add verification that tests and benchmarks do not spoil GOMAXPROCS.
Plus fix spoiling of GOMAXPROCS in 2 existing rwmutex tests.
Plus fix benchmark output to stdout (now it outputs to stderr like all other output).

[rsc, 2011-06-03 15:26:00]

To save and restore:

defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(-1))

[rsc, 2011-06-03 15:27:53]

http://codereview.appspot.com/4529111/diff/1002/src/pkg/testing/benchmark.go
File src/pkg/testing/benchmark.go (right):

http://codereview.appspot.com/4529111/diff/1002/src/pkg/testing/benchmark.go#...
src/pkg/testing/benchmark.go:199: print("The benchmark changes
runtime.GOMAXPROCS\n")
if p := runtime.GOMAXPROCS(-1); p != procs {
    print(fmt.Sprintf("%s left GOMAXPROCS set to %d\n", Benchmark.Name, p))
}

http://codereview.appspot.com/4529111/diff/1002/src/pkg/testing/testing.go
File src/pkg/testing/testing.go (right):

http://codereview.appspot.com/4529111/diff/1002/src/pkg/testing/testing.go#ne...
src/pkg/testing/testing.go:196: t.errors = "The test changes
runtime.GOMAXPROCS\n"
same wording here please

[dvyukov, 2011-06-03 17:29:11]

On 2011/06/03 15:26:00, rsc wrote:
> To save and restore:
> 
> defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(-1))

Humm... the first call must occur at function begin, while the second call must
occur at function end. I think that defer will execute both calls at function
end.
However it's a good idea to use defer. I think it should be:
procs := runtime.GOMAXPROCS(-1)
defer runtime.GOMAXPROCS(procs)

[rsc, 2011-06-03 17:30:40]

> Humm... the first call must occur at function begin, while the second
> call must occur at function end. I think that defer will execute both
> calls at function end.

No, it will work.
http://golang.org/doc/go_spec.html#Defer_statements

[dvyukov, 2011-06-03 17:43:51]

Done. Please review.

[rsc, 2011-06-03 17:50:02]

LGTM

Thanks!

[rsc, 2011-06-03 17:50:48]

*** Submitted as http://code.google.com/p/go/source/detail?r=10b268bedd1b ***

testing: check that tests and benchmarks do not affect GOMAXPROCS

Plus fix spoiling of GOMAXPROCS in 2 existing rwmutex tests.
Plus fix benchmark output to stdout (now it outputs to stderr like all other
output).

R=rsc
CC=golang-dev
http://codereview.appspot.com/4529111

Committer: Russ Cox <rsc@golang.org>