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Deadlock may result when using Reentrant services

Scope

Minor

Version Introduced

4.6.2

Source Analyzer Status

Investigating

Change Description

A deadlock may result in a Reentrant service, which restricts instances of the service to one thread of execution at a time. Services prone to encounter this problem will have the following xref:System.ServiceModel.ServiceBehaviorAttribute in their code:

[ServiceBehavior(ConcurrencyMode = ConcurrencyMode.Reentrant)]
  • Quirked
  • Build-time break

Recommended Action

To address this issue, you can do the following:

  • Set the service's concurrency mode to xref:System.ServiceModel.ConcurrencyMode.Single?displayProperty=nameWithType or <System.ServiceModel.ConcurrencyMode.Multiple?displayProperty=nameWithType>. For example:

    [ServiceBehavior(ConcurrencyMode = ConcurrencyMode.Single)]

  • Install the latest update to the .NET Framework 4.6.2, or upgrade to a later version of the .NET Framework. This disables the flow of the xref:System.Threading.ExecutionContext in xref:System.ServiceModel.OperationContext.Current?displayProperty=nameWithType. This behavior is configurable; it is equivalent to adding the following app setting to your configuration file:

    <appSettings>
   <add key="Switch.System.ServiceModel.DisableOperationContextAsyncFlow" value="true" />
</appSettings>

    The value of Switch.System.ServiceModel.DisableOperationContextAsyncFlow should never be set to false for Rentrant services.

Affected APIs

  • T:System.ServiceModel.ServiceBehaviorAttribute
  • F:System.ServiceModel.ConcurrencyMode.Reentrant

Category

Windows Communication Foundation (WCF)