rcu: Introduce rcutorture testing for rcu_barrier()

Although rcutorture does invoke rcu_barrier() and friends, it cannot
really be called a torture test given that it invokes them only once
at the end of the test.  This commit therefore introduces heavy-duty
rcutorture testing for rcu_barrier(), which may be carried out
concurrently with normal rcutorture testing.

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

1 files changed, 14 insertions, 1 deletions

diff --git a/Documentation/RCU/torture.txt b/Documentation/RCU/torture.txt
index 375d3fb71437..4ddf3913fd8c 100644
--- a/Documentation/RCU/torture.txt
+++ b/Documentation/RCU/torture.txt
@@ -47,6 +47,16 @@ irqreader	Says to invoke RCU readers from irq level.  This is currently
                 permit this.  (Or, more accurately, variants of RCU that do
                 -not- permit this know to ignore this variable.)
 
+n_barrier_cbs   If this is nonzero, RCU barrier testing will be conducted,
+                in which case n_barrier_cbs specifies the number of
+                RCU callbacks (and corresponding kthreads) to use for
+                this testing.  The value cannot be negative.  If you
+                specify this to be non-zero when torture_type indicates a
+                synchronous RCU implementation (one for which a member of
+                the synchronize_rcu() rather than the call_rcu() family is
+                used -- see the documentation for torture_type below), an
+                error will be reported and no testing will be carried out.
+
 nfakewriters    This is the number of RCU fake writer threads to run.  Fake
                 writer threads repeatedly use the synchronous "wait for
                 current readers" function of the interface selected by
@@ -188,7 +198,7 @@ OUTPUT
 The statistics output is as follows:
 
         rcu-torture:--- Start of test: nreaders=16 nfakewriters=4 stat_interval=30 verbose=0 test_no_idle_hz=1 shuffle_interval=3 stutter=5 irqreader=1 fqs_duration=0 fqs_holdoff=0 fqs_stutter=3 test_boost=1/0 test_boost_interval=7 test_boost_duration=4
-        rcu-torture: rtc:           (null) ver: 155441 tfle: 0 rta: 155441 rtaf: 8884 rtf: 155440 rtmbe: 0 rtbke: 0 rtbre: 0 rtbf: 0 rtb: 0 nt: 3055767
+        rcu-torture: rtc:           (null) ver: 155441 tfle: 0 rta: 155441 rtaf: 8884 rtf: 155440 rtmbe: 0 rtbe: 0 rtbke: 0 rtbre: 0 rtbf: 0 rtb: 0 nt: 3055767
         rcu-torture: Reader Pipe:  727860534 34213 0 0 0 0 0 0 0 0 0
         rcu-torture: Reader Batch:  727877838 17003 0 0 0 0 0 0 0 0 0
         rcu-torture: Free-Block Circulation:  155440 155440 155440 155440 155440 155440 155440 155440 155440 155440 0
@@ -230,6 +240,9 @@ o	"rtmbe": A non-zero value indicates that rcutorture believes that
         rcu_assign_pointer() and rcu_dereference() are not working
         correctly.  This value should be zero.
 
+o       "rtbe": A non-zero value indicates that one of the rcu_barrier()
+        family of functions is not working correctly.
+
 o       "rtbke": rcutorture was unable to create the real-time kthreads
         used to force RCU priority inversion.  This value should be zero.