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authorDmitry Torokhov <dmitry.torokhov@gmail.com>2016-10-14 02:25:40 +0200
committerDmitry Torokhov <dmitry.torokhov@gmail.com>2016-10-14 02:25:40 +0200
commit4a7126a25b4dfd07d61c699f724118275acc0c25 (patch)
treec78b82bfaa96f330d412ad63e355906f963c3faf /Documentation/RCU/whatisRCU.txt
parentInput: i8042 - skip selftest on ASUS laptops (diff)
parentLinux 4.8 (diff)
downloadlinux-4a7126a25b4dfd07d61c699f724118275acc0c25.tar.xz
linux-4a7126a25b4dfd07d61c699f724118275acc0c25.zip
Merge tag 'v4.8' into next
Sync up with mainline to bring in I2C host notify changes and other updates.
Diffstat (limited to 'Documentation/RCU/whatisRCU.txt')
-rw-r--r--Documentation/RCU/whatisRCU.txt25
1 files changed, 18 insertions, 7 deletions
diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt
index dc49c6712b17..204422719197 100644
--- a/Documentation/RCU/whatisRCU.txt
+++ b/Documentation/RCU/whatisRCU.txt
@@ -5,6 +5,9 @@ to start learning about RCU:
2. What is RCU? Part 2: Usage http://lwn.net/Articles/263130/
3. RCU part 3: the RCU API http://lwn.net/Articles/264090/
4. The RCU API, 2010 Edition http://lwn.net/Articles/418853/
+ 2010 Big API Table http://lwn.net/Articles/419086/
+5. The RCU API, 2014 Edition http://lwn.net/Articles/609904/
+ 2014 Big API Table http://lwn.net/Articles/609973/
What is RCU?
@@ -681,22 +684,30 @@ 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 +743,7 @@ 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 +751,15 @@ 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 }