diff options
author | Dmitry Torokhov <dmitry.torokhov@gmail.com> | 2016-10-14 02:25:40 +0200 |
---|---|---|
committer | Dmitry Torokhov <dmitry.torokhov@gmail.com> | 2016-10-14 02:25:40 +0200 |
commit | 4a7126a25b4dfd07d61c699f724118275acc0c25 (patch) | |
tree | c78b82bfaa96f330d412ad63e355906f963c3faf /Documentation/RCU/whatisRCU.txt | |
parent | Input: i8042 - skip selftest on ASUS laptops (diff) | |
parent | Linux 4.8 (diff) | |
download | linux-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.txt | 25 |
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 } |