runtime/pprof: ignore runtime-internal samples in test

Tests of the mutex profile focus on sync.Mutex, which is easy to
control. But since those tests still use the runtime, and contention on
internal runtime.mutex values is now also part of the mutex profile, we
have to filter out those samples before examining the profile. Otherwise
the test may be confused by stray contention on sched.lock (or other
runtime-internal locks) as a natural consequence of using goroutines.

Fixes #67563

Change-Id: I066a24674d8b719dbeca4a5c0f76b53bc07498c1
Reviewed-on: https://go-review.googlesource.com/c/go/+/586957
Reviewed-by: Cherry Mui <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Auto-Submit: Rhys Hiltner <[email protected]>
Reviewed-by: Michael Pratt <[email protected]>

Author: rhysh

src/runtime/pprof/pprof_test.go

@@ -1349,14 +1349,21 @@ func TestMutexProfileRateAdjust(t *testing.T) {
 		}
 
 		for _, s := range p.Sample {
+			var match, runtimeInternal bool
 			for _, l := range s.Location {
 				for _, line := range l.Line {
 					if line.Function.Name == "runtime/pprof.blockMutex.func1" {
-						contentions += s.Value[0]
-						delay += s.Value[1]
+						match = true
+					}
+					if line.Function.Name == "runtime.unlock" {
+						runtimeInternal = true
 					}
 				}
 			}
+			if match && !runtimeInternal {
+				contentions += s.Value[0]
+				delay += s.Value[1]
+			}
 		}
 		return
 	}