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

[junction.git] / junction / ConcurrentMap_Grampa.h

diff --git a/junction/ConcurrentMap_Grampa.h b/junction/ConcurrentMap_Grampa.h
index 8422b22..dc4749c 100644 (file)
--- a/junction/ConcurrentMap_Grampa.h
+++ b/junction/ConcurrentMap_Grampa.h
@@ -280,9 +280,12 @@ public:
                 m_cell = Details::find(hash, m_table, m_sizeMask);
                 if (!m_cell)
                     return;
                 m_cell = Details::find(hash, m_table, m_sizeMask);
                 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_Grampa, 11, "[Mutator] find was redirected", uptr(m_table), 0);
                 m_table->jobCoordinator.participate();
                 // We've encountered a Redirect value. Help finish the migration.
                 TURF_TRACE(ConcurrentMap_Grampa, 11, "[Mutator] find was redirected", uptr(m_table), 0);
                 m_table->jobCoordinator.participate();


@@ -307,13 +310,15 @@ public:
                     }
                     case Details::InsertResult_AlreadyFound: {
                         // The hash was already found in the table.
                     }
                     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_Grampa, 13, "[Mutator] insertOrFind was redirected", uptr(m_table), uptr(m_value));
                             break; // Help finish the migration.
                         }
                             // We've encountered a Redirect value.
                             TURF_TRACE(ConcurrentMap_Grampa, 13, "[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, overflowIdx);
                     }
                     case Details::InsertResult_Overflow: {
                         Details::beginTableMigration(m_map, m_table, overflowIdx);