Merge tag 'rcu.2023.08.21a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu

Pull RCU updates from Paul McKenney:

 - Documentation updates

 - Miscellaneous fixes, perhaps most notably simplifying
   SRCU_NOTIFIER_INIT() as suggested

 - RCU Tasks updates, most notably treating Tasks RCU callbacks as lazy
   while still treating synchronous grace periods as urgent. Also fixes
   one bug that restores the ability to apply debug-objects to RCU Tasks
   and another that fixes a race condition that could result in
   false-positive failures of the boot-time self-test code

 - RCU-scalability performance-test updates, most notably adding the
   ability to measure the RCU-Tasks's grace-period kthread's CPU
   consumption. This proved quite useful for the RCU Tasks work

 - Reference-acquisition/release performance-test updates, including a
   fix for an uninitialized wait_queue_head_t

 - Miscellaneous torture-test updates

 - Torture-test scripting updates, including removal of the
   non-longer-functional formal-verification scripts, test builds of
   individual RCU Tasks flavors, better diagnostics for loss of
   connectivity for distributed rcutorture tests, disabling of reboot
   loops in qemu/KVM-based rcutorture testing, and passing of init
   parameters to rcutorture's init program

* tag 'rcu.2023.08.21a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu: (64 commits)
  rcu: Use WRITE_ONCE() for assignments to ->next for rculist_nulls
  rcu: Make the rcu_nocb_poll boot parameter usable via boot config
  rcu: Mark __rcu_irq_enter_check_tick() ->rcu_urgent_qs load
  srcu,notifier: Remove #ifdefs in favor of SRCU Tiny srcu_usage
  rcutorture: Stop right-shifting torture_random() return values
  torture: Stop right-shifting torture_random() return values
  torture: Move stutter_wait() timeouts to hrtimers
  torture: Move torture_shuffle() timeouts to hrtimers
  torture: Move torture_onoff() timeouts to hrtimers
  torture: Make torture_hrtimeout_*() use TASK_IDLE
  torture: Add lock_torture writer_fifo module parameter
  torture: Add a kthread-creation callback to _torture_create_kthread()
  rcu-tasks: Fix boot-time RCU tasks debug-only deadlock
  rcu-tasks: Permit use of debug-objects with RCU Tasks flavors
  checkpatch: Complain about unexpected uses of RCU Tasks Trace
  torture: Cause mkinitrd.sh to indicate failure on compile errors
  torture: Make init program dump command-line arguments
  torture: Switch qemu from -nographic to -display none
  torture: Add init-program support for loongarch
  torture: Avoid torture-test reboot loops
  ...

1 files changed, 4 insertions, 3 deletions

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 147551c23baf..ade42d6a9d9b 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1581,6 +1581,7 @@ rcu_torture_writer(void *arg)
 				    rcu_access_pointer(rcu_torture_current) !=
 				    &rcu_tortures[i]) {
 					tracing_off();
+					show_rcu_gp_kthreads();
 					WARN(1, "%s: rtort_pipe_count: %d\n", __func__, rcu_tortures[i].rtort_pipe_count);
 					rcu_ftrace_dump(DUMP_ALL);
 				}
@@ -1876,7 +1877,7 @@ static int
 rcutorture_extend_mask(int oldmask, struct torture_random_state *trsp)
 {
 	int mask = rcutorture_extend_mask_max();
-	unsigned long randmask1 = torture_random(trsp) >> 8;
+	unsigned long randmask1 = torture_random(trsp);
 	unsigned long randmask2 = randmask1 >> 3;
 	unsigned long preempts = RCUTORTURE_RDR_PREEMPT | RCUTORTURE_RDR_SCHED;
 	unsigned long preempts_irq = preempts | RCUTORTURE_RDR_IRQ;
@@ -1935,7 +1936,7 @@ rcutorture_loop_extend(int *readstate, struct torture_random_state *trsp,
 	if (!((mask - 1) & mask))
 		return rtrsp;  /* Current RCU reader not extendable. */
 	/* Bias towards larger numbers of loops. */
-	i = (torture_random(trsp) >> 3);
+	i = torture_random(trsp);
 	i = ((i | (i >> 3)) & RCUTORTURE_RDR_MAX_LOOPS) + 1;
 	for (j = 0; j < i; j++) {
 		mask = rcutorture_extend_mask(*readstate, trsp);
@@ -2136,7 +2137,7 @@ static int rcu_nocb_toggle(void *arg)
 		toggle_fuzz = NSEC_PER_USEC;
 	do {
 		r = torture_random(&rand);
-		cpu = (r >> 4) % (maxcpu + 1);
+		cpu = (r >> 1) % (maxcpu + 1);
 		if (r & 0x1) {
 			rcu_nocb_cpu_offload(cpu);
 			atomic_long_inc(&n_nocb_offload);