rcu: Eliminate flavor scan in rcu_momentary_dyntick_idle()

The rcu_momentary_dyntick_idle() function scans the RCU flavors, checking
that one of them still needs a quiescent state before doing an expensive
atomic operation on the ->dynticks counter.  However, this check reduces
overhead only after a rare race condition, and increases complexity.  This
commit therefore removes the scan and the mechanism enabling the scan.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/Documentation/RCU/Design/Data-Structures/Data-Structures.html b/Documentation/RCU/Design/Data-Structures/Data-Structures.html
index 3d0311657533..e4bf20a68fa3 100644
--- a/Documentation/RCU/Design/Data-Structures/Data-Structures.html
+++ b/Documentation/RCU/Design/Data-Structures/Data-Structures.html
@@ -1104,7 +1104,7 @@ Its fields are as follows:
   1   int dynticks_nesting;
   2   int dynticks_nmi_nesting;
   3   atomic_t dynticks;
-  4   int rcu_sched_qs_mask;
+  4   bool rcu_need_heavy_qs;
   5   unsigned long rcu_qs_ctr;
 </pre>
 
@@ -1124,7 +1124,7 @@ CPU's transitions to and from dyntick-idle mode, so that this counter
 has an even value when the CPU is in dyntick-idle mode and an odd
 value otherwise.
 
-</p><p>The <tt>-&gt;rcu_sched_qs_mask</tt> field is used
+</p><p>The <tt>-&gt;rcu_need_heavy_qs</tt> field is used
 to record the fact that the RCU core code would really like to
 see a quiescent state from the corresponding CPU, so much so that
 it is willing to call for heavy-weight dyntick-counter operations.