libgo patch committed: Make NumGoroutine wait for system goroutines to register

[Ian Lance Taylor <iant at golang dot org>]

In libgo system goroutines register themselves after they start.  That
means that there is a small race between the goroutine being seen by
the scheduler and the scheduler knowing that the goroutine is a system
goroutine. That in turn means that runtime.NumGoroutines can
overestimate the number of goroutines at times.

This patch fixes the overestimate by counting the number of system
goroutines waiting to start, and pausing NumGoroutines until those
goroutines have all registered.

This is kind of a lot of mechanism for this not very important
problem, but I couldn't think of a better approach.

The test for this is TestNumGoroutine in runtime/proc_test.go.  The
test is not currently run, but it will be soon.

Bootstrapped and ran Go testsuite on x86_64-pc-linux-gnu.  Committed
to mainline.

Ian

Attachment: patch.txt
Description: Text document