rcutorture: Allow negative values of nreaders to oversubscribe

By default, with rcutorture.nreaders equal to -1, rcutorture provisions
N-1 reader kthreads, where N is the number of CPUs.  This avoids
rcutorture-induced stalls, but also avoids heavier levels of torture.
This commit therefore allows negative values of rcutorture.nreaders
to specify larger numbers of reader kthreads, so that for example
rcutorture.nreaders=-2 provisions N kthreads and rcutorture.nreaders=-5
provisions N+3 kthreads.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: Update documentation, as suggested by Josh Triplett. ]

1 files changed, 1 insertions, 1 deletions

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index a67ef6ff86b0..7294d605c481 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1701,7 +1701,7 @@ rcu_torture_init(void)
         if (nreaders >= 0) {
                 nrealreaders = nreaders;
         } else {
-                nrealreaders = num_online_cpus() - 1;
+                nrealreaders = num_online_cpus() - 2 - nreaders;
                 if (nrealreaders <= 0)
                         nrealreaders = 1;
         }