rcutorture: Add races with task-exit processing

Several variants of Linux-kernel RCU interact with task-exit processing,
including preemptible RCU, Tasks RCU, and Tasks Trace RCU.  This commit
therefore adds testing of this interaction to rcutorture by adding
rcutorture.read_exit_burst and rcutorture.read_exit_delay kernel-boot
parameters.  These kernel parameters control the frequency and spacing
of special read-then-exit kthreads that are spawned.

[ paulmck: Apply feedback from Dan Carpenter's static checker. ]
[ paulmck: Reduce latency to avoid false-positive shutdown hangs. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/include/linux/torture.h b/include/linux/torture.h
index 629b66e6c161..7f65bd1dd307 100644
--- a/include/linux/torture.h
+++ b/include/linux/torture.h
@@ -55,6 +55,11 @@ struct torture_random_state {
 #define DEFINE_TORTURE_RANDOM_PERCPU(name) \
 	DEFINE_PER_CPU(struct torture_random_state, name)
 unsigned long torture_random(struct torture_random_state *trsp);
+static inline void torture_random_init(struct torture_random_state *trsp)
+{
+	trsp->trs_state = 0;
+	trsp->trs_count = 0;
+}
 
 /* Task shuffler, which causes CPUs to occasionally go idle. */
 void torture_shuffle_task_register(struct task_struct *tp);