From 0ca4f6be35d2abf54128b57c3aa1a1fcbd5adfe3 Mon Sep 17 00:00:00 2001 From: David Finkel Date: Wed, 31 Jul 2019 09:10:28 -0400 Subject: [PATCH] runtime/pprof: Mention goroutine label heritability Document goroutine label inheritance. Goroutine labels are copied upon goroutine creation and there is a test enforcing this, but it was not mentioned in the docstrings for `Do` or `SetGoroutineLabels`. Add notes to both of those functions' docstrings so it's clear that one does not need to set labels as soon as a new goroutine is spawned if they want to propagate tags. Updates #32223 Updates #23458 Change-Id: Idfa33031af0104b884b03ca855ac82b98500c8b4 Reviewed-on: https://go-review.googlesource.com/c/go/+/189317 Reviewed-by: Ian Lance Taylor --- src/runtime/pprof/runtime.go | 2 ++ 1 file changed, 2 insertions(+) diff --git a/src/runtime/pprof/runtime.go b/src/runtime/pprof/runtime.go index e6aace83e2..b71bbad9a6 100644 --- a/src/runtime/pprof/runtime.go +++ b/src/runtime/pprof/runtime.go @@ -16,6 +16,7 @@ func runtime_setProfLabel(labels unsafe.Pointer) func runtime_getProfLabel() unsafe.Pointer // SetGoroutineLabels sets the current goroutine's labels to match ctx. +// A new goroutine inherits the labels of the goroutine that created it. // This is a lower-level API than Do, which should be used instead when possible. func SetGoroutineLabels(ctx context.Context) { ctxLabels, _ := ctx.Value(labelContextKey{}).(*labelMap) @@ -24,6 +25,7 @@ func SetGoroutineLabels(ctx context.Context) { // Do calls f with a copy of the parent context with the // given labels added to the parent's label map. +// Goroutines spawned while executing f will inherit the augmented label-set. // Each key/value pair in labels is inserted into the label map in the // order provided, overriding any previous value for the same key. // The augmented label map will be set for the duration of the call to f -- 2.50.0