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: Yao Dongdong <yaodongdong@huawei.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt
index dc49c6712b17ff4968d3c4fdf2b304e0292fb5be..111770ffa10e7cc4c3d2dada09e1e85f8d576099 100644 (file)
--- a/Documentation/RCU/whatisRCU.txt
+++ b/Documentation/RCU/whatisRCU.txt
@@ -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 }