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Commit 70946a44 authored by Yao Dongdong's avatar Yao Dongdong Committed by Paul E. McKenney
Browse files

documentation: Make sample code and documentation consistent 



In the chapter 'analogy with reader-writer locking', the sample
code uses spinlock_t in reader-writer case. Just correct it so
that we can read the document easily.

Signed-off-by: default avatarYao Dongdong <yaodongdong@huawei.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 274529ba

Documentation/RCU/whatisRCU.txt

+15 −7
Original line number Diff line number Diff line
@@ -681,22 +681,30 @@ Although RCU can be used in many different ways, a very common use of 
RCU is analogous to reader-writer locking.  The following unified

diff shows how closely related RCU and reader-writer locking can be.



	@@ -5,5 +5,5 @@ struct el {

	 	int data;

	 	/* Other data fields */

	 };

	-rwlock_t listmutex;

	+spinlock_t listmutex;

	 struct el head;



	@@ -13,15 +14,15 @@

		struct list_head *lp;

		struct el *p;



	-	read_lock();

	-	read_lock(&listmutex);

	-	list_for_each_entry(p, head, lp) {

	+	rcu_read_lock();

	+	list_for_each_entry_rcu(p, head, lp) {

			if (p->key == key) {

				*result = p->data;

	-			read_unlock();

	-			read_unlock(&listmutex);

	+			rcu_read_unlock();

				return 1;

			}

		}

	-	read_unlock();

	-	read_unlock(&listmutex);

	+	rcu_read_unlock();

		return 0;

	 }
@@ -732,7 +740,7 @@ Or, for those who prefer a side-by-side listing: 
 5   int data;                          5   int data;

 6   /* Other data fields */            6   /* Other data fields */

 7 };                                   7 };

 8 spinlock_t listmutex;                8 spinlock_t listmutex;

 8 rwlock_t listmutex;                  8 spinlock_t listmutex;

 9 struct el head;                      9 struct el head;



 1 int search(long key, int *result)    1 int search(long key, int *result)
@@ -740,15 +748,15 @@ Or, for those who prefer a side-by-side listing: 
 3   struct list_head *lp;              3   struct list_head *lp;

 4   struct el *p;                      4   struct el *p;

 5                                      5

 6   read_lock();                       6   rcu_read_lock();

 6   read_lock(&listmutex);             6   rcu_read_lock();

 7   list_for_each_entry(p, head, lp) { 7   list_for_each_entry_rcu(p, head, lp) {

 8     if (p->key == key) {             8     if (p->key == key) {

 9       *result = p->data;             9       *result = p->data;

10       read_unlock();                10       rcu_read_unlock();

10       read_unlock(&listmutex);      10       rcu_read_unlock();

11       return 1;                     11       return 1;

12     }                               12     }

13   }                                 13   }

14   read_unlock();                    14   rcu_read_unlock();

14   read_unlock(&listmutex);          14   rcu_read_unlock();

15   return 0;                         15   return 0;

16 }                                   16 }