Merge tag 'rcu.2022.01.09a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu

Pull RCU updates from Paul McKenney:

 - Documentation updates, perhaps most notably Neil Brown's writeup of
   the reference-counting analogy to RCU.

 - Expedited grace-period cleanups.

 - Remove CONFIG_RCU_FAST_NO_HZ due to lack of valid users. I have asked
   around, posted a blog entry, and sent this series to LKML without
   result.

 - Miscellaneous fixes.

 - RCU callback offloading updates, perhaps most notably Frederic
   Weisbecker's updates allowing CPUs booted in the de-offloaded state
   to be offloaded at runtime.

 - nolibc fixes from Willy Tarreau and Anmar Faizi, but also including
   Mark Brown's addition of gettid().

 - RCU Tasks Trace fixes, including changes that increase the
   scalability of call_rcu_tasks_trace() for the BPF folks (Martin Lau
   and KP Singh).

 - Various fixes including those from Wander Lairson Costa and Li
   Zhijian.

 - Fixes plus addition of tests for the increased call_rcu_tasks_trace()
   scalability.

* tag 'rcu.2022.01.09a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu: (87 commits)
  rcu/nocb: Merge rcu_spawn_cpu_nocb_kthread() and rcu_spawn_one_nocb_kthread()
  rcu/nocb: Allow empty "rcu_nocbs" kernel parameter
  rcu/nocb: Create kthreads on all CPUs if "rcu_nocbs=" or "nohz_full=" are passed
  rcu/nocb: Optimize kthreads and rdp initialization
  rcu/nocb: Prepare nocb_cb_wait() to start with a non-offloaded rdp
  rcu/nocb: Remove rcu_node structure from nocb list when de-offloaded
  rcu-tasks: Use fewer callbacks queues if callback flood ends
  rcu-tasks: Use separate ->percpu_dequeue_lim for callback dequeueing
  rcu-tasks: Use more callback queues if contention encountered
  rcu-tasks: Avoid raw-spinlocked wakeups from call_rcu_tasks_generic()
  rcu-tasks: Count trylocks to estimate call_rcu_tasks() contention
  rcu-tasks: Add rcupdate.rcu_task_enqueue_lim to set initial queueing
  rcu-tasks: Make rcu_barrier_tasks*() handle multiple callback queues
  rcu-tasks: Use workqueues for multiple rcu_tasks_invoke_cbs() invocations
  rcu-tasks: Abstract invocations of callbacks
  rcu-tasks: Abstract checking of callback lists
  rcu-tasks: Add a ->percpu_enqueue_lim to the rcu_tasks structure
  rcu-tasks: Inspect stalled task's trc state in locked state
  rcu-tasks: Use spin_lock_rcu_node() and friends
  rcutorture: Combine n_max_cbs from all kthreads in a callback flood
  ...

1 files changed, 24 insertions, 26 deletions

diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
index 1631ef8a138d..5489ff7f478e 100644
--- a/kernel/rcu/refscale.c
+++ b/kernel/rcu/refscale.c
@@ -44,7 +44,10 @@
 	pr_alert("%s" SCALE_FLAG s, scale_type, ## x)
 
 #define VERBOSE_SCALEOUT(s, x...) \
-	do { if (verbose) pr_alert("%s" SCALE_FLAG s, scale_type, ## x); } while (0)
+	do { \
+		if (verbose) \
+			pr_alert("%s" SCALE_FLAG s "\n", scale_type, ## x); \
+	} while (0)
 
 static atomic_t verbose_batch_ctr;
 
@@ -54,12 +57,11 @@ do {											\
 	    (verbose_batched <= 0 ||							\
 	     !(atomic_inc_return(&verbose_batch_ctr) % verbose_batched))) {		\
 		schedule_timeout_uninterruptible(1);					\
-		pr_alert("%s" SCALE_FLAG s, scale_type, ## x);				\
+		pr_alert("%s" SCALE_FLAG s "\n", scale_type, ## x);			\
 	}										\
 } while (0)
 
-#define VERBOSE_SCALEOUT_ERRSTRING(s, x...) \
-	do { if (verbose) pr_alert("%s" SCALE_FLAG "!!! " s, scale_type, ## x); } while (0)
+#define SCALEOUT_ERRSTRING(s, x...) pr_alert("%s" SCALE_FLAG "!!! " s "\n", scale_type, ## x)
 
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Joel Fernandes (Google) <joel@joelfernandes.org>");
@@ -604,7 +606,7 @@ static u64 process_durations(int n)
 	char *buf;
 	u64 sum = 0;
 
-	buf = kmalloc(128 + nreaders * 32, GFP_KERNEL);
+	buf = kmalloc(800 + 64, GFP_KERNEL);
 	if (!buf)
 		return 0;
 	buf[0] = 0;
@@ -617,13 +619,15 @@ static u64 process_durations(int n)
 
 		if (i % 5 == 0)
 			strcat(buf, "\n");
+		if (strlen(buf) >= 800) {
+			pr_alert("%s", buf);
+			buf[0] = 0;
+		}
 		strcat(buf, buf1);
 
 		sum += rt->last_duration_ns;
 	}
-	strcat(buf, "\n");
-
-	SCALEOUT("%s\n", buf);
+	pr_alert("%s\n", buf);
 
 	kfree(buf);
 	return sum;
@@ -637,7 +641,6 @@ static u64 process_durations(int n)
 // point all the timestamps are printed.
 static int main_func(void *arg)
 {
-	bool errexit = false;
 	int exp, r;
 	char buf1[64];
 	char *buf;
@@ -648,10 +651,10 @@ static int main_func(void *arg)
 
 	VERBOSE_SCALEOUT("main_func task started");
 	result_avg = kzalloc(nruns * sizeof(*result_avg), GFP_KERNEL);
-	buf = kzalloc(64 + nruns * 32, GFP_KERNEL);
+	buf = kzalloc(800 + 64, GFP_KERNEL);
 	if (!result_avg || !buf) {
-		VERBOSE_SCALEOUT_ERRSTRING("out of memory");
-		errexit = true;
+		SCALEOUT_ERRSTRING("out of memory");
+		goto oom_exit;
 	}
 	if (holdoff)
 		schedule_timeout_interruptible(holdoff * HZ);
@@ -663,8 +666,6 @@ static int main_func(void *arg)
 
 	// Start exp readers up per experiment
 	for (exp = 0; exp < nruns && !torture_must_stop(); exp++) {
-		if (errexit)
-			break;
 		if (torture_must_stop())
 			goto end;
 
@@ -698,26 +699,23 @@ static int main_func(void *arg)
 	// Print the average of all experiments
 	SCALEOUT("END OF TEST. Calculating average duration per loop (nanoseconds)...\n");
 
-	if (!errexit) {
-		buf[0] = 0;
-		strcat(buf, "\n");
-		strcat(buf, "Runs\tTime(ns)\n");
-	}
-
+	pr_alert("Runs\tTime(ns)\n");
 	for (exp = 0; exp < nruns; exp++) {
 		u64 avg;
 		u32 rem;
 
-		if (errexit)
-			break;
 		avg = div_u64_rem(result_avg[exp], 1000, &rem);
 		sprintf(buf1, "%d\t%llu.%03u\n", exp + 1, avg, rem);
 		strcat(buf, buf1);
+		if (strlen(buf) >= 800) {
+			pr_alert("%s", buf);
+			buf[0] = 0;
+		}
 	}
 
-	if (!errexit)
-		SCALEOUT("%s", buf);
+	pr_alert("%s", buf);
 
+oom_exit:
 	// This will shutdown everything including us.
 	if (shutdown) {
 		shutdown_start = 1;
@@ -841,12 +839,12 @@ ref_scale_init(void)
 	reader_tasks = kcalloc(nreaders, sizeof(reader_tasks[0]),
 			       GFP_KERNEL);
 	if (!reader_tasks) {
-		VERBOSE_SCALEOUT_ERRSTRING("out of memory");
+		SCALEOUT_ERRSTRING("out of memory");
 		firsterr = -ENOMEM;
 		goto unwind;
 	}
 
-	VERBOSE_SCALEOUT("Starting %d reader threads\n", nreaders);
+	VERBOSE_SCALEOUT("Starting %d reader threads", nreaders);
 
 	for (i = 0; i < nreaders; i++) {
 		firsterr = torture_create_kthread(ref_scale_reader, (void *)i,