EventCounters unexpectedly stop reporting data when first of two listeners disconnects

[noahfalk]

Description

One our internal partner teams at Microsoft reported that if they start an EventListener for EventCounters, then separately start PerfView to listen to counters, then stop the PerfView session the counter information stops flowing to their EventListener. Given that the EventListener never stopped listening they expected the counter events to continue.

Reproduction Steps

Start EventListener for EventCounters, then start + stop a PerfView ETW based session for the same counter events.

Expected behavior

Counter events continue to be posted to EventListener

Actual behavior

Counter events stop being posted

Regression?

Unknown, but probably not

Known Workarounds

No response

Configuration

I think this is .NET Core 6 (preview builds), amd64, but the issue probably occurs regardless of version/architecture

Other information

The code for CounterGroup appears to stop sending upon receiving a Disable command from any listener, regardless of the presence of other listeners. https://github.com/dotnet/runtime/blob/v5.0.11/src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/CounterGroup.cs#L67

[dpk83]

@noahfalk Is this issue only impacting .NET 6 or earlier versions as well? Is the fix going to be backported to all affected versions?

[davmason]

@dpk83 this issue affects all runtimes that have support for dotnet-counters. A fix has not been checked in yet for this issue, when it is we will not backport it unless there is a business justification for it - i.e. a customer is blocked on it.