CTS.TryReset() concurrency issue

[sakno]

Description

A full description of the issue is here: #60180

Reproduction Steps

1. Create CTS
2. Call CancelAfter with very small timeout (1-10 milliseconds)
3. Call TryReset concurrently with CancelAfter

Expected behavior

TryReset should normally handle the concurrency with timer cancellation and return true/false.

Actual behavior

System.ObjectDisposedException : Cannot access a disposed object.
  Stack Trace:
 at System.Threading.TimerQueueTimer.Change(UInt32 dueTime, UInt32 period)
 at System.Threading.CancellationTokenSource.TryReset()

Regression?

No, TryReset is introduced in .NET 6.

Known Workarounds

Do not use TryReset at all and re-create CTS every time when needed.

or

catch ObjectDisposedException by the caller:

static bool TryResetSafe(CancellationTokenSource source)
{
  try
  {
    return source.TryReset();
  }
  catch (ObjectDisposedException)
  {
    return false;
  }
}

Configuration

The environment is not relevant. .NET SDK version is 6.0.100-rc.1.21458.32

Other information

No response

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Issue Details

---

Description

A full description of the issue is here: #60180

Reproduction Steps

1. Create CTS
2. Call CancelAfter with very small timeout (1-10 milliseconds)
3. Call TryReset concurrently with CancelAfter

Expected behavior

TryReset should normally handle the concurrency with timer cancellation and return true/false.

Actual behavior

System.ObjectDisposedException : Cannot access a disposed object.
  Stack Trace:
 at System.Threading.TimerQueueTimer.Change(UInt32 dueTime, UInt32 period)
 at System.Threading.CancellationTokenSource.TryReset()

Regression?

No, TryReset is introduced in .NET 6.

Known Workarounds

Do not use TryReset at all and re-create CTS every time when needed.

Configuration

The environment is not relevant. .NET SDK version is 6.0.100-rc.1.21458.32

Other information

No response

Author:	sakno
Assignees:	stephentoub
Labels:	area-System.Threading, untriaged
Milestone:	-

[sakno]

@stephentoub , I pushed draft PR but couldn't test it because of changes in CoreCLR codebase.

/projects/dotnet/src/coreclr/jit/morph.cpp:67:35: error: assigning to 'var_types' from incompatible type 'unsigned char'
      call->gtReturnType          = static_cast<unsigned char>(tree->TypeGet());

[sakno]

My bad, sorry. I changed target branch from main to release/6.0-rc2.

[sakno]

@stephentoub , two PRs are here as discussed previously:

• Fix: CTS.TryReset() concurrency issue #60182 #60224 with quick fix
• Alternative fix of #60182 #60298 with long-term fix

[stephentoub]

thanks!

[danmoseley]

@stephentoub is there remaining 6.0 work here? or can we close now?

[stephentoub]

is there remaining 6.0 work here?

No, #60323 should have closed it. Not sure why it didn't; maybe that bot doesn't have perms to do so.