rcu: Increase rcutorture test coverage

Currently, rcutorture has separate torture_types to test synchronous,
asynchronous, and expedited grace-period primitives.  This has
two disadvantages: (1) Three times the number of runs to cover the
combinations and (2) Little testing of concurrent combinations of the
three options.  This commit therefore adds a pair of module parameters
that control normal and expedited state, with the default being both
types, randomly selected, by the fakewriter processes, thus reducing
source-code size and increasing test coverage.  In addtion, the writer
task switches between asynchronous-normal and expedited grace-period
primitives driven by the same pair of module parameters.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

1 files changed, 10 insertions, 0 deletions

diff --git a/Documentation/RCU/torture.txt b/Documentation/RCU/torture.txt
index d8a502387397..dac02a6219b1 100644
--- a/Documentation/RCU/torture.txt
+++ b/Documentation/RCU/torture.txt
@@ -42,6 +42,16 @@ fqs_holdoff	Holdoff time (in microseconds) between consecutive calls
 fqs_stutter     Wait time (in seconds) between consecutive bursts
                 of calls to force_quiescent_state().
 
+gp_normal       Make the fake writers use normal synchronous grace-period
+                primitives.
+
+gp_exp          Make the fake writers use expedited synchronous grace-period
+                primitives.  If both gp_normal and gp_exp are set, or
+                if neither gp_normal nor gp_exp are set, then randomly
+                choose the primitive so that about 50% are normal and
+                50% expedited.  By default, neither are set, which
+                gives best overall test coverage.
+
 irqreader       Says to invoke RCU readers from irq level.  This is currently
                 done via timers.  Defaults to "1" for variants of RCU that
                 permit this.  (Or, more accurately, variants of RCU that do