Dead lock when getting dynamic parameters for `Install-Package` while PSRL is running

[SeeminglyScience]

I've been looking at what PowerShell says is running every time I've hit a dead lock. Every time, it's Install-Package generating dynamic parameters.

Repro

1. Install module ImpliedReflection (or other preferred reflection module)

2. Wait for a dead lock after completion

3. Get the process ID of the integrated console with Get-PSHostProcess (Hint: it won't have a window title)

4. Enter the process with Enter-PSHostProcess

5. Get the main PSIC runspace with $rs = Get-Runspace 2

6. Enable implied reflection with Enable-ImpliedReflection

7. Navigate to $rs.ExecutionContext.CurrentCommandProcessor. Should look something like this:

   Click to expand output

   FromScriptFile                   : False
   _cmdletParameterBinderController : System.Management.Automation.CmdletParameterBinderController
   u_obsoleteAttribute              :
   _firstCallToRead                 : True
   _bailInNextCall                  : False
   RanBeginAlready                  : False
   _addedToPipelineAlready          : False
   _fromScriptFile                  : False
   CommandRuntime                   : Install-Package
   _useLocalScope                   : True
   _context                         : System.Management.Automation.ExecutionContext
   arguments                        : {}
   CmdletParameterBinderController  : System.Management.Automation.CmdletParameterBinderController
   ObsoleteAttribute                :
   AddedToPipelineAlready           : False
   CommandInfo                      : Install-Package
   RedirectShellErrorOutputPipe     : False
   Command                          : Microsoft.PowerShell.PackageManagement.Cmdlets.InstallPackage
   UseLocalScope                    : True
   Context                          : System.Management.Automation.ExecutionContext
   PipelineActivityId               : 00000000-0000-0000-0000-000000000000
   CommandSessionState              : System.Management.Automation.SessionStateInternal
   CommandScope                     : System.Management.Automation.SessionStateScope
   

8. Navigate to $rs.ExecutionContext.CurrentCommandProcessor.Command. Should look something like this:

   Click to expand output

   InputObject                      :
   Name                             :
   RequiredVersion                  :
   MinimumVersion                   :
   MaximumVersion                   :
   Source                           :
   Credential                       :
   Proxy                            :
   ProxyCredential                  :
   Sources                          : {}
   WebProxy                         :
   CredentialUsername               :
   CredentialPassword               :
   AllVersions                      : False
   ProviderName                     :
   MessageResolver                  :
   DynamicOptions                   : {}
   OptionKeys                       : {}
   IsInteractive                    : False
   CallCount                        : 2
   WhatIf                           : False
   IsCanceled                       : False
   DynamicParameterDictionary       : {}
   ParameterSetName                 : PackageBySearch
   MyInvocation                     : System.Management.Automation.InvocationInfo
   PagingParameters                 :
   InvokeCommand                    : System.Management.Automation.CommandInvocationIntrinsics
   Host                             : System.Management.Automation.Internal.Host.InternalHost
   SessionState                     : System.Management.Automation.SessionState
   Events                           : System.Management.Automation.PSLocalEventManager
   JobRepository                    : System.Management.Automation.JobRepository
   JobManager                       : System.Management.Automation.JobManager
   InvokeProvider                   : System.Management.Automation.ProviderIntrinsics
   Stopping                         : False
   CommandRuntime                   : Install-Package
   CurrentPSTransaction             :
   CommandOrigin                    : Internal
   Force                            : False
   ForceBootstrap                   : False
   <InputObject>k__BackingField     :
   <Name>k__BackingField            :
   <RequiredVersion>k__BackingField :
   <MinimumVersion>k__BackingField  :
   <MaximumVersion>k__BackingField  :
   _resultsPerName                  : {}
   _providersNotFindingAnything     : {}
   IsFailingEarly                   : False
   UserSpecifiedSourcesList         : {}
   CmdletState                      : GenerateParameters
   CancellationEvent                : System.Threading.CancellationTokenSource
   ErrorState                       : False
   currentObjectInPipeline          :
   CommandOriginInternal            : Internal
   ParameterSets                    : {PackageBySearch, PackageByInputObject}
   SpecifiedMinimumOrMaximum        : False
   BootstrapNuGet                   : true
   SelectedProviders                : {Programs, msu, msi, NuGet...}
   CachedSelectedProviders          : {Programs, msu, msi, NuGet...}
   CachedDynamicOptions             : {IncludeWindowsInstaller, IncludeSystemComponent, AdditionalArguments,
                                       ConfigFile...}
   CachedStaticParameters           :
   IsDisplayCulture                 : False
   UseDefaultSourceFormat           : True
   ShouldLogError                   : True
   ShouldSelectAllProviders         : False
   IsPackageBySearch                : True
   IsPackageByObject                : False
   IsSourceByObject                 : False
   PackageManagementService         : Microsoft.PackageManagement.Internal.Implementation.PackageManagementService
   TimeOut                          : 3600
   Responsiveness                   : 900
   PackageManagementHost            : IHostApi_proxy_20
   IsReentrantLocked                : True
   Confirm                          : False
   IsInvocation                     : False
   HasErrors                        : False
   UnboundArguments                 : {}
   IsProcessing                     : False
   IsBeforeProcessing               : True
   IsAfterProcessing                : False
   HasDynamicParameters             : True
   RunspaceRepository               : System.Management.Automation.RunspaceRepository
   _ParameterSetName                : PackageBySearch
   InvocationExtent                 :
   CurrentPipelineObject            :
   PSHostInternal                   : System.Management.Automation.Internal.Host.InternalHost
   InternalState                    : System.Management.Automation.SessionState
   IsStopping                       : False
   CommandInfo                      : Install-Package
   Context                          : System.Management.Automation.ExecutionContext
   

PackageManagement makes heavy use of async in their cmdlets. My guess is they are inheriting our single threaded background synchronization context when they previously were not.

Note: Cancelling the command via their internal API ($rs.ExecutionContext.CurrentCommandProcessor.Command.Cancel()) doesn't do anything, which makes sense if it's a threading related dead lock.

[SeeminglyScience]

This is a bit more complicated than I initially expected.

Series of events

1. PSReadLine is running in the main pipeline thread
2. In the editor, some portion of the cmdlet Install-Package is typed
3. A completion request is triggered for the typed text
4. We take over the pipeline thread via an OnIdle event subscriber
5. The GetDynamicParameters method is called on Install-Package during CompleteInput
6. Install-Package enters a new thread
7. Install-Package calls MyInvocation.MyCommand.Parameters
8. The getter for the Parameters property then creates an event to get back onto the pipeline thread
9. Dead lock

Gathered points of interest

• The call to CommandInfo.Parameters in PackageManagement

• CommandInfo.Parameters

• GetMergedCommandParameterMetadataSafely

• The branch that completions takes in PSES

• The ultimate InvokeOnPipelineThread method called, that queues up an invocation request for
  the event subscriber to handle

• Where that invocation request is ultimately invoked

[rjmholt]

Tagging @daxian-dbw, @PaulHigin, @BrucePay and @lzybkr, since we are in need of some expertise of PowerShell's threaded behaviour. Essentially our usage of PSReadLine is resulting in a deadlock with the PackageManagement cmdlets inside PowerShell, and we're not entirely sure how to get around it.

I've read over the possibly related PowerShell/PowerShell#4003, but ultimately we need this to work in Windows PowerShell as well.

We'd be very appreciative of any advice you can offer. I'm sure we can give proper explanations of PSES' implementation wherever needed (good exercise for us anyway).

[lzybkr]

If PSReadLine is running, the PowerShell engine is "busy" because the function PSConsoleReadLine is running.

In the early PSReadLine days, folks noticed their OnIdle events weren't processed until after PSReadLine finished.

This is currently broken in 2.0, see PowerShell/PSReadLine#773.

I don't know when this regressed (no regression tests for this unfortunately), but the VSCode/PSReadLine is a likely candidate to have caused the regression.

I'd start with fixing PowerShell/PSReadLine#773 and maybe this deadlock will be fixed.

[SeeminglyScience]

@lzybkr The OnIdle event is definitely working, the dead lock happens while CommandCompletion.CompleteInput() is running after already taking the thread from PSReadLine. Also this is only an issue when Install-Package (and most likely other cmdlets from PackageManagement) are a part of the completion results.

I believe the problem is that Install-Package puts itself on another thread to generate parameters, then accesses a property that tries to put itself back onto the pipeline thread with an event. But the first event (for command completion) is still running.

[lzybkr]

OK, I hadn't looked at the OnIdle issue yet, but from your description, it sounds like the problem would reproduce without PSReadLine. Maybe @jianyunt has some insight here.

[jianyunt]

PackageManagement indeed is using async and dynamics a lot. GetDynamicParameters is called here: https://github.com/OneGet/oneget/blob/173df840e345d0a753dd0a9dec684e394f1b22ea/src/Microsoft.PowerShell.PackageManagement/Cmdlets/CmdletWithProvider.cs#L426

But we have not heard deadlock from other users though.

[SeeminglyScience]

@jianyunt Yeah it's not a particularly common scenario so I'm not surprised it hasn't come up. Here's an easy way to reproduce it outside of VSCode:

$splat = @{
    SourceIdentifer = [System.Management.Automation.PSEngineEvent]::OnIdle
    Action = { (Get-Command Install-Package).Parameters }
}

Register-EngineEvent @splat 

If you run that the prompt will become unresponsive.

I've fixed the issue by saving MyInvocation.MyCommand.Parameters prior to calling AsyncRun, that clears up the deadlock. I can submit a PR after some more testing.

[jianyunt]

👍