Writing
rcu_assign_pointer() and rcu_xchg_pointer() may be called anywhere.
- After, synchronize_rcu() must be called. When it returns, the old values
- are not in usage anymore.
+ After, synchronize_rcu() must be called. When it returns, the old
+ values are not in usage anymore.
+Being careful with signals
-Usage of DEBUG_FULL_MB
+ The library uses signals internally. The signal handler is
+ registered with the SA_RESTART flag. However, these signals may cause
+ some non-restartable system calls to fail with errno = EINTR. Care
+ should be taken to restart system calls manually if they fail with this
+ error. A list of non-restartable system calls may be found in
+ signal(7). To ensure the Userspace RCU library does not use signals,
+ define CONFIG_URCU_AVOID_SIGNALS at compile-time.
- DEBUG_FULL_MB uses full SMP barriers for readers. This eliminates the
- need for signals but results in slower reads.
+ Read-side critical sections can sit in a signal handler. Be careful,
+ however, to disable these signals between thread creation and calls to
+ rcu_register_thread(), because a signal handler nesting on an
+ unregistered thread would not be allowed to call rcu_read_lock().
+Usage of CONFIG_URCU_AVOID_SIGNALS
+
+ CONFIG_URCU_AVOID_SIGNALS uses full SMP barriers for readers. This
+ eliminates the need for signals but results in slower reads.
+
+Usage of DEBUG_RCU
+
+ DEBUG_RCU is used to add internal debugging self-checks to the
+ RCU library. This define adds a performance penality when enabled.
Usage of DEBUG_YIELD
DEBUG_YIELD is used to add random delays in the code for testing
purposes.
-