[PATCH] RCU: add fake writers to rcutorture

rcutorture currently has one writer and an arbitrary number of readers.  To
better exercise some of the code paths in RCU implementations, add fake
writer threads which call the synchronize function for the RCU variant in a
loop, with a delay between calls to arrange for different numbers of
writers running in parallel.

[bunk@stusta.de: cleanup]
Acked-by: Paul McKenney <paulmck@us.ibm.com>
Cc: Dipkanar Sarma <dipankar@in.ibm.com>
Signed-off-by: Josh Triplett <josh@freedesktop.org>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/Documentation/RCU/torture.txt b/Documentation/RCU/torture.txt
index 2174badd31e0..2180ef93accc 100644
--- a/Documentation/RCU/torture.txt
+++ b/Documentation/RCU/torture.txt
@@ -28,6 +28,15 @@ nreaders	This is the number of RCU reading threads supported.
                 To properly exercise RCU implementations with preemptible
                 read-side critical sections.
 
+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
+                torture_type, with a delay between calls to allow for various
+                different numbers of writers running in parallel.
+                nfakewriters defaults to 4, which provides enough parallelism
+                to trigger special cases caused by multiple writers, such as
+                the synchronize_srcu() early return optimization.
+
 stat_interval   The number of seconds between output of torture
                 statistics (via printk()).  Regardless of the interval,
                 statistics are printed when the module is unloaded.