cmd/trace: also show end stack traces

Fix a regression that appeared in 1.23 when it comes to the stack traces
shown in the trace viewer. In 1.22 and earlier, the viewer was always
showing end stack traces. In 1.23 and later the viewer started to
exclusively show start stack traces.

Showing only the start stack traces made it impossible to see the last
stack trace produced by a goroutine. It also made it hard to understand
why a goroutine went off-cpu, as one had to hunt down the next running
slice of the same goroutine.

Emit end stack traces in addition to start stack traces to fix the
issue.

Fixes #70570

Change-Id: Ib22ea61388c1d94cdbc99fae2d207c4dce011a59
Reviewed-on: https://go-review.googlesource.com/c/go/+/631895
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
Auto-Submit: Felix Geisendörfer <felix.geisendoerfer@datadoghq.com>
Reviewed-by: Nick Ripley <nick.ripley@datadoghq.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>

diff --git a/src/cmd/trace/gstate.go b/src/cmd/trace/gstate.go
index ea501ef57d561e4dafc4d839a7c4e457202652cf..c883166e06da2ea1f894dd48a52cafba7f12217e 100644 (file)
--- a/src/cmd/trace/gstate.go
+++ b/src/cmd/trace/gstate.go
@@ -257,6 +257,10 @@ func (gs *gState[R]) stop(ts trace.Time, stack trace.Stack, ctx *traceContext) {
        if gs.lastStopStack != trace.NoStack {
                stk = ctx.Stack(viewerFrames(gs.lastStopStack))
        }
+       var endStk int
+       if stack != trace.NoStack {
+               endStk = ctx.Stack(viewerFrames(stack))
+       }
        // Check invariants.
        if gs.startRunningTime == 0 {
                panic("silently broken trace or generator invariant (startRunningTime != 0) not held")
@@ -270,6 +274,7 @@ func (gs *gState[R]) stop(ts trace.Time, stack trace.Stack, ctx *traceContext) {
                Dur:      ts.Sub(gs.startRunningTime),
                Resource: uint64(gs.executing),
                Stack:    stk,
+               EndStack: endStk,
        })
 
        // Flush completed ranges.