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Extend Dictionary concurrent access detection to Remove() #18524

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danmoseley merged 2 commits into from
Jun 20, 2018
Merged

Extend Dictionary concurrent access detection to Remove() #18524

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1f772e7
added concurrent access detection to Remove()
MarcoRossignoli Jun 18, 2018
7c33e68
Merge branch 'master' into dicrem
MarcoRossignoli Jun 19, 2018
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52 changes: 36 additions & 16 deletions src/System.Private.CoreLib/shared/System/Collections/Generic/Dictionary.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -758,27 +758,30 @@ public bool Remove(TKey key)
ThrowHelper.ThrowArgumentNullException(ExceptionArgument.key);
}

if (_buckets != null)
int[] buckets = _buckets;
Entry[] entries = _entries;
int collisionCount = 0;
if (buckets != null)
{
int hashCode = (_comparer?.GetHashCode(key) ?? key.GetHashCode()) & 0x7FFFFFFF;
int bucket = hashCode % _buckets.Length;
int bucket = hashCode % buckets.Length;
int last = -1;
// Value in _buckets is 1-based
int i = _buckets[bucket] - 1;
// Value in buckets is 1-based
int i = buckets[bucket] - 1;
while (i >= 0)
{
ref Entry entry = ref _entries[i];
ref Entry entry = ref entries[i];

if (entry.hashCode == hashCode && (_comparer?.Equals(entry.key, key) ?? EqualityComparer<TKey>.Default.Equals(entry.key, key)))
{
if (last < 0)
{
// Value in _buckets is 1-based
_buckets[bucket] = entry.next + 1;
// Value in buckets is 1-based
buckets[bucket] = entry.next + 1;
}
else
{
_entries[last].next = entry.next;
entries[last].next = entry.next;
}
entry.hashCode = -1;
entry.next = _freeList;
Expand All @@ -799,6 +802,13 @@ public bool Remove(TKey key)

last = i;
i = entry.next;
if (collisionCount >= entries.Length)
{
// The chain of entries forms a loop; which means a concurrent update has happened.
// Break out of the loop and throw, rather than looping forever.
ThrowHelper.ThrowInvalidOperationException_ConcurrentOperationsNotSupported();
}
collisionCount++;
}
}
return false;
Expand All @@ -814,27 +824,30 @@ public bool Remove(TKey key, out TValue value)
ThrowHelper.ThrowArgumentNullException(ExceptionArgument.key);
}

if (_buckets != null)
int[] buckets = _buckets;
Entry[] entries = _entries;
int collisionCount = 0;
if (buckets != null)
{
int hashCode = (_comparer?.GetHashCode(key) ?? key.GetHashCode()) & 0x7FFFFFFF;
int bucket = hashCode % _buckets.Length;
int bucket = hashCode % buckets.Length;
int last = -1;
// Value in _buckets is 1-based
int i = _buckets[bucket] - 1;
// Value in buckets is 1-based
int i = buckets[bucket] - 1;
while (i >= 0)
{
ref Entry entry = ref _entries[i];
ref Entry entry = ref entries[i];

if (entry.hashCode == hashCode && (_comparer?.Equals(entry.key, key) ?? EqualityComparer<TKey>.Default.Equals(entry.key, key)))
{
if (last < 0)
{
// Value in _buckets is 1-based
_buckets[bucket] = entry.next + 1;
// Value in buckets is 1-based
buckets[bucket] = entry.next + 1;
}
else
{
_entries[last].next = entry.next;
entries[last].next = entry.next;
}

value = entry.value;
Expand All @@ -858,6 +871,13 @@ public bool Remove(TKey key, out TValue value)

last = i;
i = entry.next;
if (collisionCount >= entries.Length)
{
// The chain of entries forms a loop; which means a concurrent update has happened.
// Break out of the loop and throw, rather than looping forever.
ThrowHelper.ThrowInvalidOperationException_ConcurrentOperationsNotSupported();
}
collisionCount++;
}
}
value = default;
Expand Down