runtime: do not inherit labels on system goroutines

GC background mark worker goroutines are created when the first GC is
triggered (or next GC after GOMAXPROCS increases). Since the GC can be
triggered from a user goroutine, those workers will inherit any pprof
labels from the user goroutine.

That isn't meaningful, so avoid it by excluding system goroutines from
inheriting labels.

Fixes #50032

Change-Id: Ib425ae561a3466007ff5deec86b9c51829ab5507
Reviewed-on: https://go-review.googlesource.com/c/go/+/369983
Reviewed-by: Austin Clements <austin@google.com>
Trust: Michael Pratt <mpratt@google.com>
Run-TryBot: Michael Pratt <mpratt@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index 7509f7632f47037ca129c1823fe4d1eaf40d26fe..eee0a25fee78fd105bd9b6890f8aaff63c0c4b47 100644 (file)
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -4300,11 +4300,13 @@ func newproc1(fn *funcval, callergp *g, callerpc uintptr) *g {
        newg.gopc = callerpc
        newg.ancestors = saveAncestors(callergp)
        newg.startpc = fn.fn
-       if _g_.m.curg != nil {
-               newg.labels = _g_.m.curg.labels
-       }
        if isSystemGoroutine(newg, false) {
                atomic.Xadd(&sched.ngsys, +1)
+       } else {
+               // Only user goroutines inherit pprof labels.
+               if _g_.m.curg != nil {
+                       newg.labels = _g_.m.curg.labels
+               }
        }
        // Track initial transition?
        newg.trackingSeq = uint8(fastrand())