README

   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). To ensure the Userspace RCU library does not use signals,
  40         define CONFIG_URCU_AVOID_SIGNALS at compile-time.
  41
  42         Read-side critical sections can sit in a signal handler. Be careful,
  43         however, to disable these signals between thread creation and calls to
  44         rcu_register_thread(), because a signal handler nesting on an
  45         unregistered thread would not be allowed to call rcu_read_lock().
  46
  47 Usage of CONFIG_URCU_AVOID_SIGNALS
  48
  49         CONFIG_URCU_AVOID_SIGNALS uses full SMP barriers for readers. This
  50         eliminates the need for signals but results in slower reads.
  51
  52 Usage of DEBUG_RCU
  53
  54         DEBUG_RCU is used to add internal debugging self-checks to the
  55         RCU library. This define adds a performance penality when enabled.
  56         Can be enabled by uncommenting the corresponding line in
  57         Makefile.build.inc.
  58
  59 Usage of DEBUG_YIELD
  60
  61         DEBUG_YIELD is used to add random delays in the code for testing
  62         purposes.