ref(logs): no longer enter Counter-Scopes when a Lock-Scope has been …

…entered successfully

src/Sentry/Threading/ScopedCountdownLock.cs

@@ -31,16 +31,16 @@ internal ScopedCountdownLock()
     /// Gets the number of remaining <see cref="CounterScope"/> required to exit in order to set/signal the event while a <see cref="LockScope"/> is active.
     /// When <see langword="0"/> and while a <see cref="LockScope"/> is active, no more <see cref="CounterScope"/> can be entered.
     /// </summary>
-    internal int Count => _isEngaged == 1 ? _event.CurrentCount : _event.CurrentCount - 1;
+    internal int Count => IsEngaged ? _event.CurrentCount : _event.CurrentCount - 1;
 
     /// <summary>
     /// Returns <see langword="true"/> when a <see cref="LockScope"/> is active and the event can be set/signaled by <see cref="Count"/> reaching <see langword="0"/>.
     /// Returns <see langword="false"/> when the <see cref="Count"/> can only reach the initial count of <see langword="1"/> when no <see cref="CounterScope"/> is active any longer.
     /// </summary>
-    internal bool IsEngaged => _isEngaged == 1;
+    internal bool IsEngaged => Interlocked.CompareExchange(ref _isEngaged, 1, 1) == 1;
 
     /// <summary>
-    /// No <see cref="CounterScope"/> will be entered when the <see cref="Count"/> has reached <see langword="0"/> while the lock is engaged via an active <see cref="LockScope"/>.
+    /// No <see cref="CounterScope"/> will be entered when the <see cref="Count"/> has reached <see langword="0"/>, or while the lock is engaged via an active <see cref="LockScope"/>.
     /// Check via <see cref="CounterScope.IsEntered"/> whether the underlying <see cref="CountdownEvent"/> has not been set/signaled yet.
     /// To signal the underlying <see cref="CountdownEvent"/>, ensure <see cref="CounterScope.Dispose"/> is called.
     /// </summary>
@@ -49,6 +49,11 @@ internal ScopedCountdownLock()
     /// </remarks>
     internal CounterScope TryEnterCounterScope()
     {
+        if (IsEngaged)
+        {
+            return new CounterScope();
+        }
+
         if (_event.TryAddCount(1))
         {
             return new CounterScope(this);

test/Sentry.Tests/Threading/ScopedCountdownLockTests.cs

@@ -79,20 +79,20 @@ public void TryEnterLockScope_IsEngaged_IsSet()
         lockTwo.Dispose();
         AssertEngaged(false, 1);
 
-        // successfully enter another CounterScope ... lock is engaged but not yet set
+        // cannot enter another CounterScope as long as the lock is already engaged by a LockScope
         var counterTwo = _lock.TryEnterCounterScope();
-        counterTwo.IsEntered.Should().BeTrue();
-        AssertEngaged(false, 2);
+        counterTwo.IsEntered.Should().BeFalse();
+        AssertEngaged(false, 1);
 
-        // exit a CounterScope ... decrement the count
+        // no-op ... CounterScope is not entered
         counterTwo.Dispose();
         AssertEngaged(false, 1);
 
         // exit last CounterScope ... count of engaged lock reaches zero ... sets the lock
         counterOne.Dispose();
         AssertEngaged(true, 0);
 
-        // cannot enter another CounterScope as long as the engaged lock is set
+        // cannot enter another CounterScope as long as the lock is engaged and set
         var counterThree = _lock.TryEnterCounterScope();
         counterThree.IsEntered.Should().BeFalse();
         AssertEngaged(true, 0);
@@ -102,11 +102,11 @@ public void TryEnterLockScope_IsEngaged_IsSet()
         // would block if the count of the engaged lock was not zero
         lockOne.Wait();
 
-        // exit the LockScope ... reset the lock
+        // exit the LockScope ... reset and disengage the lock
         lockOne.Dispose();
         AssertDisengaged(false, 0);
 
-        // can enter a CounterScope again ... the lock not set
+        // can enter a CounterScope again ... the lock is no longer set and no longer engaged
         var counterFour = _lock.TryEnterCounterScope();
         counterFour.IsEntered.Should().BeTrue();
         AssertDisengaged(false, 1);