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, 7 insertions, 5 deletions

diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
index 949d3deae506..270c7f80ce84 100644
--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -45,6 +45,7 @@ torture_param(int, stutter, 5, "Number of jiffies to run/halt test, 0=disable");
 torture_param(int, rt_boost, 2,
 		   "Do periodic rt-boost. 0=Disable, 1=Only for rt_mutex, 2=For all lock types.");
 torture_param(int, rt_boost_factor, 50, "A factor determining how often rt-boost happens.");
+torture_param(int, writer_fifo, 0, "Run writers at sched_set_fifo() priority");
 torture_param(int, verbose, 1, "Enable verbose debugging printk()s");
 torture_param(int, nested_locks, 0, "Number of nested locks (max = 8)");
 /* Going much higher trips "BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!" errors */
@@ -809,7 +810,8 @@ static int lock_torture_writer(void *arg)
 	bool skip_main_lock;
 
 	VERBOSE_TOROUT_STRING("lock_torture_writer task started");
-	set_user_nice(current, MAX_NICE);
+	if (!rt_task(current))
+		set_user_nice(current, MAX_NICE);
 
 	do {
 		if ((torture_random(&rand) & 0xfffff) == 0)
@@ -1015,8 +1017,7 @@ static void lock_torture_cleanup(void)
 
 	if (writer_tasks) {
 		for (i = 0; i < cxt.nrealwriters_stress; i++)
-			torture_stop_kthread(lock_torture_writer,
-					     writer_tasks[i]);
+			torture_stop_kthread(lock_torture_writer, writer_tasks[i]);
 		kfree(writer_tasks);
 		writer_tasks = NULL;
 	}
@@ -1244,8 +1245,9 @@ static int __init lock_torture_init(void)
 			goto create_reader;
 
 		/* Create writer. */
-		firsterr = torture_create_kthread(lock_torture_writer, &cxt.lwsa[i],
-						  writer_tasks[i]);
+		firsterr = torture_create_kthread_cb(lock_torture_writer, &cxt.lwsa[i],
+						     writer_tasks[i],
+						     writer_fifo ? sched_set_fifo : NULL);
 		if (torture_init_error(firsterr))
 			goto unwind;