src/patches/suse-2.6.27.25/patches.trace/rcu-read-sched.patch

   1 From: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
   2 Subject: RCU read sched
   3
   4 Add rcu_read_lock_sched() and rcu_read_unlock_sched() to rcupdate.h to match the
   5 recently added write-side call_rcu_sched() and rcu_barrier_sched(). They also
   6 match the no-so-recently-added synchronize_sched().
   7
   8 It will help following matching use of the update/read lock primitives. Those
   9 new read lock will replace preempt_disable()/enable() used in pair with
  10 RCU-classic synchronization.
  11
  12 Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
  13 Acked-by: Peter Zijlstra <peterz@infradead.org>
  14 CC: Paul E McKenney <paulmck@linux.vnet.ibm.com>
  15 CC: akpm@linux-foundation.org
  16 Acked-by: Jan Blunck <jblunck@suse.de>
  17 ---
  18  include/linux/rcupdate.h |   20 ++++++++++++++++++++
  19  1 file changed, 20 insertions(+)
  20
  21 --- a/include/linux/rcupdate.h
  22 +++ b/include/linux/rcupdate.h
  23 @@ -133,6 +133,26 @@ struct rcu_head {
  24  #define rcu_read_unlock_bh() __rcu_read_unlock_bh()
  25
  26  /**
  27 + * rcu_read_lock_sched - mark the beginning of a RCU-classic critical section
  28 + *
  29 + * Should be used with either
  30 + * - synchronize_sched()
  31 + * or
  32 + * - call_rcu_sched() and rcu_barrier_sched()
  33 + * on the write-side to insure proper synchronization.
  34 + */
  35 +#define rcu_read_lock_sched() preempt_disable()
  36 +
  37 +/*
  38 + * rcu_read_unlock_sched - marks the end of a RCU-classic critical section
  39 + *
  40 + * See rcu_read_lock_sched for more information.
  41 + */
  42 +#define rcu_read_unlock_sched() preempt_enable()
  43 +
  44 +
  45 +
  46 +/**
  47   * rcu_dereference - fetch an RCU-protected pointer in an
  48   * RCU read-side critical section.  This pointer may later
  49   * be safely dereferenced.