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POWhy should Next() operation of a singly linked list be protected with a critical section?
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I'm reading the book Multithreading Applications in Win32 The book says <code>return node->next</code> will be compiled into separate machine instructions that would not be executed as an atomic operation, so <code>Next()</code> should also be protected by the critical section. My question is, what instructions could it be translated into, to cause a race condition? <pre><code>typedef struct _Node { struct Node *next; int data; } Node; typedef struct _List { Node *head; CRITICAL SECTION critical_sec; } List; List *CreateList() { List *pList = malloc(sizeof(List)); pList->head = NULL; InitializeCriticalSection(&pList->critical_sec); return pList; } void DeleteList(List *pList) { DeleteCriticalSection(&pList->critical_sec); free(pList); } void AddHead(List *pList, Node *node) { EnterCriticalSection(&pList->critical_sec); node->next = pList->head; pList->head = node; LeaveCriticalSection(&pList->critical_sec); } void Insert(List *pList, Node *afterNode, Node *newNode) { EnterCriticalSection(&pList->critical_sec); if (afterNode == NULL) { AddHead(pList, newNode); } else { newNode->next = afterNode->next; afterNode->next = newNode; } LeaveCriticalSection(&pList->critical_sec); } Node *Next(List *pList, Node *node) { Node* next; EnterCriticalSection(&pList->critical_sec); next = node->next; LeaveCriticalSection(&pList->critical_sec); return next; } </code></pre> Edit: OK, although in this particular case it won't corrupt the singly linked list w/o protecting the <code>Next()</code> operation, a shared structure should be protected as a whole or nothing, generally.
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<c++><multithreading><winapi>
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Why should Next() operation of a singly linked list be protected with a critical section?
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