Fix #31: Entries can disappear when deleted key is reassigned during a migration

[junction.git] / junction / ConcurrentMap_Linear.h

diff --git a/junction/ConcurrentMap_Linear.h b/junction/ConcurrentMap_Linear.h
index 6e74efacf0a2b5ddb67b5c9882de1d354ec6cf3a..6799c916e557aaf2a16e70b0b5c8c887e2a0764b 100644 (file)
--- a/junction/ConcurrentMap_Linear.h
+++ b/junction/ConcurrentMap_Linear.h
@@ -81,9 +81,12 @@ public:
                 m_cell = Details::find(hash, m_table);
                 if (!m_cell)
                     return;
-                m_value = m_cell->value.load(turf::Consume);
-                if (m_value != Value(ValueTraits::Redirect))
-                    return; // Found an existing value
+                Value value = m_cell->value.load(turf::Consume);
+                if (value != Value(ValueTraits::Redirect)) {
+                    // Found an existing value
+                    m_value = value;
+                    return;
+                }
                 // We've encountered a Redirect value. Help finish the migration.
                 TURF_TRACE(ConcurrentMap_Linear, 1, "[Mutator] find was redirected", uptr(m_table), 0);
                 m_table->jobCoordinator.participate();
@@ -105,13 +108,15 @@ public:
                 }
                 case Details::InsertResult_AlreadyFound: {
                     // The hash was already found in the table.
-                    m_value = m_cell->value.load(turf::Consume);
-                    if (m_value == Value(ValueTraits::Redirect)) {
+                    Value value = m_cell->value.load(turf::Consume);
+                    if (value == Value(ValueTraits::Redirect)) {
                         // We've encountered a Redirect value.
                         TURF_TRACE(ConcurrentMap_Linear, 3, "[Mutator] insertOrFind was redirected", uptr(m_table), uptr(m_value));
                         break; // Help finish the migration.
                     }
-                    return; // Found an existing value
+                    // Found an existing value
+                    m_value = value;
+                    return;
                 }
                 case Details::InsertResult_Overflow: {
                     Details::beginTableMigration(m_map, m_table, mustDouble);