| 1 | Userspace RCU Implementatation |
| 2 | by Mathieu Desnoyers and Paul E. McKenney |
| 3 | |
| 4 | BUILDING |
| 5 | -------- |
| 6 | |
| 7 | make |
| 8 | make install |
| 9 | |
| 10 | |
| 11 | QUICK START GUIDE |
| 12 | ----------------- |
| 13 | |
| 14 | Initialization |
| 15 | |
| 16 | Each thread that has reader critical sections (that uses |
| 17 | rcu_read_lock()/rcu_read_unlock() must first register to the URCU |
| 18 | library. This is done by calling rcu_register_thread(). |
| 19 | |
| 20 | Reading |
| 21 | |
| 22 | Reader critical sections must be protected by locating them between |
| 23 | calls to rcu_read_lock() and rcu_read_unlock(). Inside that lock, |
| 24 | rcu_dereference() may be called to read an RCU protected pointer. |
| 25 | |
| 26 | Writing |
| 27 | |
| 28 | rcu_assign_pointer() and rcu_xchg_pointer() may be called anywhere. |
| 29 | After, synchronize_rcu() must be called. When it returns, the old |
| 30 | values are not in usage anymore. |
| 31 | |
| 32 | Being careful with signals |
| 33 | |
| 34 | The library uses signals internally. The signal handler is |
| 35 | registered with the SA_RESTART flag. However, these signals may cause |
| 36 | some non-restartable system calls to fail with errno = EINTR. Care |
| 37 | should be taken to restart system calls manually if they fail with this |
| 38 | error. A list of non-restartable system calls may be found in |
| 39 | signal(7). |
| 40 | |
| 41 | Usage of DEBUG_FULL_MB |
| 42 | |
| 43 | DEBUG_FULL_MB uses full SMP barriers for readers. This eliminates the |
| 44 | need for signals but results in slower reads. |
| 45 | |
| 46 | |
| 47 | Usage of DEBUG_YIELD |
| 48 | |
| 49 | DEBUG_YIELD is used to add random delays in the code for testing |
| 50 | purposes. |
| 51 | |