[PATCH rcu 0/7] Torture-test updates for v5.15

[PATCH rcu 0/7] Torture-test updates for v5.15

[Paul E. McKenney]

Hello!

This series contains updates to the in-kernel torture tests:

1.	Add measurement of clock readout.

2.	Preempt rather than block when testing task stalls.

3.	Console output claims too few grace periods, courtesy of
	"Jiangong.Han".

4.	Mark statistics data races.

5.	Count lock readers.

6.	Add RPC-like IPI tests.

7.	Avoid NULL pointer exception on early exit.

						Thanx, Paul

------------------------------------------------------------------------

 b/kernel/locking/locktorture.c |   16 ++++----
 b/kernel/rcu/rcuscale.c        |    4 +-
 b/kernel/rcu/rcutorture.c      |    7 +++
 b/kernel/rcu/refscale.c        |   37 +++++++++++++++++++
 b/kernel/scftorture.c          |   76 +++++++++++++++++++++++++++++++++--------
 kernel/locking/locktorture.c   |    9 ++--
 kernel/scftorture.c            |    2 -
 7 files changed, 121 insertions(+), 30 deletions(-)

[PATCH rcu 1/7] refscale: Add measurement of clock readout

[Paul E. McKenney]

This commit adds a "clock" type to refscale, which checks the performance
of ktime_get_real_fast_ns().  Use the "clocksource=" kernel boot parameter
to select the underlying clock source.

[ paulmck: Work around compiler false positive per kernel test robot. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/refscale.c | 37 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 36 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
index d998a76fb5422..cba737cb246e8 100644
--- a/kernel/rcu/refscale.c
+++ b/kernel/rcu/refscale.c
@@ -467,6 +467,41 @@ static struct ref_scale_ops acqrel_ops = {
 	.name		= "acqrel"
 };
 
+static volatile u64 stopopts;
+
+static void ref_clock_section(const int nloops)
+{
+	u64 x = 0;
+	int i;
+
+	preempt_disable();
+	for (i = nloops; i >= 0; i--) {
+		x += ktime_get_real_fast_ns();
+	}
+	preempt_enable();
+	stopopts = x;
+}
+
+static void ref_clock_delay_section(const int nloops, const int udl, const int ndl)
+{
+	u64 x = 0;
+	int i;
+
+	preempt_disable();
+	for (i = nloops; i >= 0; i--) {
+		x += ktime_get_real_fast_ns();
+		un_delay(udl, ndl);
+	}
+	preempt_enable();
+	stopopts = x;
+}
+
+static struct ref_scale_ops clock_ops = {
+	.readsection	= ref_clock_section,
+	.delaysection	= ref_clock_delay_section,
+	.name		= "clock"
+};
+
 static void rcu_scale_one_reader(void)
 {
 	if (readdelay <= 0)
@@ -759,7 +794,7 @@ ref_scale_init(void)
 	int firsterr = 0;
 	static struct ref_scale_ops *scale_ops[] = {
 		&rcu_ops, &srcu_ops, &rcu_trace_ops, &rcu_tasks_ops, &refcnt_ops, &rwlock_ops,
-		&rwsem_ops, &lock_ops, &lock_irq_ops, &acqrel_ops,
+		&rwsem_ops, &lock_ops, &lock_irq_ops, &acqrel_ops, &clock_ops,
 	};
 
 	if (!torture_init_begin(scale_type, verbose))
-- 
2.31.1.189.g2e36527f23

[PATCH rcu 2/7] rcutorture: Preempt rather than block when testing task stalls

[Paul E. McKenney]

Currently, rcu_torture_stall() does a one-jiffy timed wait when
stall_cpu_block is set.  This works, but emits a pointless splat in
CONFIG_PREEMPT=y kernels.  This commit avoids this splat by instead
invoking preempt_schedule() in CONFIG_PREEMPT=y kernels.

This uses an admittedly ugly #ifdef, but abstracted approaches just
looked worse.  A prettier approach would provide a preempt_schedule()
definition with a WARN_ON() for CONFIG_PREEMPT=n kernels, but this seems
quite silly.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/rcutorture.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 40ef5417d9545..ab4215266ebee 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -2022,8 +2022,13 @@ static int rcu_torture_stall(void *args)
 			  __func__, raw_smp_processor_id());
 		while (ULONG_CMP_LT((unsigned long)ktime_get_seconds(),
 				    stop_at))
-			if (stall_cpu_block)
+			if (stall_cpu_block) {
+#ifdef CONFIG_PREEMPTION
+				preempt_schedule();
+#else
 				schedule_timeout_uninterruptible(HZ);
+#endif
+			}
 		if (stall_cpu_irqsoff)
 			local_irq_enable();
 		else if (!stall_cpu_block)
-- 
2.31.1.189.g2e36527f23

[PATCH rcu 3/7] rcuscale: Console output claims too few grace periods

[Paul E. McKenney]

From: "Jiangong.Han" <jiangong.han@windriver.com>

The rcuscale console output claims N grace periods, numbered from zero
to N, which means that there were really N+1 grace periods.  The root
cause of this bug is that rcu_scale_writer() stores the number of the
last grace period (numbered from zero) into writer_n_durations[me]
instead of the number of grace periods.  This commit therefore assigns
the actual number of grace periods to writer_n_durations[me], and also
makes the corresponding adjustment to the loop outputting per-grace-period
measurements.

Sample of old console output:
    rcu-scale: writer 0 gps: 133
    ......
    rcu-scale:    0 writer-duration:     0 44003961
    rcu-scale:    0 writer-duration:     1 32003582
    ......
    rcu-scale:    0 writer-duration:   132 28004391
    rcu-scale:    0 writer-duration:   133 27996410

Sample of new console output:
    rcu-scale: writer 0 gps: 134
    ......
    rcu-scale:    0 writer-duration:     0 44003961
    rcu-scale:    0 writer-duration:     1 32003582
    ......
    rcu-scale:    0 writer-duration:   132 28004391
    rcu-scale:    0 writer-duration:   133 27996410

Signed-off-by: Jiangong.Han <jiangong.han@windriver.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/rcuscale.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c
index dca51fe9c73f2..2cc34a22a5060 100644
--- a/kernel/rcu/rcuscale.c
+++ b/kernel/rcu/rcuscale.c
@@ -487,7 +487,7 @@ rcu_scale_writer(void *arg)
 	if (gp_async) {
 		cur_ops->gp_barrier();
 	}
-	writer_n_durations[me] = i_max;
+	writer_n_durations[me] = i_max + 1;
 	torture_kthread_stopping("rcu_scale_writer");
 	return 0;
 }
@@ -561,7 +561,7 @@ rcu_scale_cleanup(void)
 			wdpp = writer_durations[i];
 			if (!wdpp)
 				continue;
-			for (j = 0; j <= writer_n_durations[i]; j++) {
+			for (j = 0; j < writer_n_durations[i]; j++) {
 				wdp = &wdpp[j];
 				pr_alert("%s%s %4d writer-duration: %5d %llu\n",
 					scale_type, SCALE_FLAG,
-- 
2.31.1.189.g2e36527f23

[PATCH rcu 4/7] locktorture: Mark statistics data races

[Paul E. McKenney]

The lock_stress_stats structure's ->n_lock_fail and ->n_lock_acquired
fields are incremented and sampled locklessly using plain C-language
statements, which KCSAN objects to.  This commit therefore marks the
statistics gathering with data_race() to flag the intent.  While in
the area, this commit also reduces the number of accesses to the
->n_lock_acquired field, thus eliminating some possible check/use
confusion.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/locking/locktorture.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
index b3adb40549bf3..313d5e613fbe6 100644
--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -738,20 +738,22 @@ static int lock_torture_reader(void *arg)
 static void __torture_print_stats(char *page,
 				  struct lock_stress_stats *statp, bool write)
 {
+	long cur;
 	bool fail = false;
 	int i, n_stress;
-	long max = 0, min = statp ? statp[0].n_lock_acquired : 0;
+	long max = 0, min = statp ? data_race(statp[0].n_lock_acquired) : 0;
 	long long sum = 0;
 
 	n_stress = write ? cxt.nrealwriters_stress : cxt.nrealreaders_stress;
 	for (i = 0; i < n_stress; i++) {
-		if (statp[i].n_lock_fail)
+		if (data_race(statp[i].n_lock_fail))
 			fail = true;
-		sum += statp[i].n_lock_acquired;
-		if (max < statp[i].n_lock_acquired)
-			max = statp[i].n_lock_acquired;
-		if (min > statp[i].n_lock_acquired)
-			min = statp[i].n_lock_acquired;
+		cur = data_race(statp[i].n_lock_acquired);
+		sum += cur;
+		if (max < cur)
+			max = cur;
+		if (min > cur)
+			min = cur;
 	}
 	page += sprintf(page,
 			"%s:  Total: %lld  Max/Min: %ld/%ld %s  Fail: %d %s\n",
-- 
2.31.1.189.g2e36527f23

[PATCH rcu 5/7] locktorture: Count lock readers

[Paul E. McKenney]

Currently, the lock_is_read_held variable is bool, so that a reader sets
it to true just after lock acquisition and then to false just before
lock release.  This works in a rough statistical sense, but can result
in false negatives just after one of a pair of concurrent readers has
released the lock.  This approach does have low overhead, but at the
expense of the setting to true potentially never leaving the reader's
store buffer, thus resulting in an unconditional false negative.

This commit therefore converts this variable to atomic_t and makes
the reader use atomic_inc() just after acquisition and atomic_dec()
just before release.  This does increase overhead, but this increase is
negligible compared to the 10-microsecond lock hold time.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/locking/locktorture.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
index 313d5e613fbe6..7c5a4a087cc73 100644
--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -59,7 +59,7 @@ static struct task_struct **writer_tasks;
 static struct task_struct **reader_tasks;
 
 static bool lock_is_write_held;
-static bool lock_is_read_held;
+static atomic_t lock_is_read_held;
 static unsigned long last_lock_release;
 
 struct lock_stress_stats {
@@ -682,7 +682,7 @@ static int lock_torture_writer(void *arg)
 		if (WARN_ON_ONCE(lock_is_write_held))
 			lwsp->n_lock_fail++;
 		lock_is_write_held = true;
-		if (WARN_ON_ONCE(lock_is_read_held))
+		if (WARN_ON_ONCE(atomic_read(&lock_is_read_held)))
 			lwsp->n_lock_fail++; /* rare, but... */
 
 		lwsp->n_lock_acquired++;
@@ -717,13 +717,13 @@ static int lock_torture_reader(void *arg)
 			schedule_timeout_uninterruptible(1);
 
 		cxt.cur_ops->readlock(tid);
-		lock_is_read_held = true;
+		atomic_inc(&lock_is_read_held);
 		if (WARN_ON_ONCE(lock_is_write_held))
 			lrsp->n_lock_fail++; /* rare, but... */
 
 		lrsp->n_lock_acquired++;
 		cxt.cur_ops->read_delay(&rand);
-		lock_is_read_held = false;
+		atomic_dec(&lock_is_read_held);
 		cxt.cur_ops->readunlock(tid);
 
 		stutter_wait("lock_torture_reader");
@@ -998,7 +998,6 @@ static int __init lock_torture_init(void)
 		}
 
 		if (nreaders_stress) {
-			lock_is_read_held = false;
 			cxt.lrsa = kmalloc_array(cxt.nrealreaders_stress,
 						 sizeof(*cxt.lrsa),
 						 GFP_KERNEL);
-- 
2.31.1.189.g2e36527f23

[PATCH rcu 6/7] scftorture: Add RPC-like IPI tests

[Paul E. McKenney]

This commit adds the single_weight_rpc module parameter, which causes the
IPI handler to awaken the IPI sender.  In many scheduler configurations,
this will result in an IPI back to the sender that is likely to be
received at a time when the sender CPU is idle.  The intent is to stress
IPI reception during CPU busy-to-idle transitions.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/scftorture.c | 76 +++++++++++++++++++++++++++++++++++++--------
 1 file changed, 63 insertions(+), 13 deletions(-)

diff --git a/kernel/scftorture.c b/kernel/scftorture.c
index 29e8fc5d91a7b..5cf40e4383191 100644
--- a/kernel/scftorture.c
+++ b/kernel/scftorture.c
@@ -64,6 +64,7 @@ torture_param(bool, use_cpus_read_lock, 0, "Use cpus_read_lock() to exclude CPU
 torture_param(int, verbose, 0, "Enable verbose debugging printk()s");
 torture_param(int, weight_resched, -1, "Testing weight for resched_cpu() operations.");
 torture_param(int, weight_single, -1, "Testing weight for single-CPU no-wait operations.");
+torture_param(int, weight_single_rpc, -1, "Testing weight for single-CPU RPC operations.");
 torture_param(int, weight_single_wait, -1, "Testing weight for single-CPU operations.");
 torture_param(int, weight_many, -1, "Testing weight for multi-CPU no-wait operations.");
 torture_param(int, weight_many_wait, -1, "Testing weight for multi-CPU operations.");
@@ -86,6 +87,8 @@ struct scf_statistics {
 	long long n_resched;
 	long long n_single;
 	long long n_single_ofl;
+	long long n_single_rpc;
+	long long n_single_rpc_ofl;
 	long long n_single_wait;
 	long long n_single_wait_ofl;
 	long long n_many;
@@ -101,14 +104,17 @@ static DEFINE_PER_CPU(long long, scf_invoked_count);
 // Data for random primitive selection
 #define SCF_PRIM_RESCHED	0
 #define SCF_PRIM_SINGLE		1
-#define SCF_PRIM_MANY		2
-#define SCF_PRIM_ALL		3
-#define SCF_NPRIMS		7 // Need wait and no-wait versions of each,
-				  //  except for SCF_PRIM_RESCHED.
+#define SCF_PRIM_SINGLE_RPC	2
+#define SCF_PRIM_MANY		3
+#define SCF_PRIM_ALL		4
+#define SCF_NPRIMS		8 // Need wait and no-wait versions of each,
+				  //  except for SCF_PRIM_RESCHED and
+				  //  SCF_PRIM_SINGLE_RPC.
 
 static char *scf_prim_name[] = {
 	"resched_cpu",
 	"smp_call_function_single",
+	"smp_call_function_single_rpc",
 	"smp_call_function_many",
 	"smp_call_function",
 };
@@ -128,6 +134,8 @@ struct scf_check {
 	bool scfc_out;
 	int scfc_cpu; // -1 for not _single().
 	bool scfc_wait;
+	bool scfc_rpc;
+	struct completion scfc_completion;
 };
 
 // Use to wait for all threads to start.
@@ -158,6 +166,7 @@ static void scf_torture_stats_print(void)
 		scfs.n_resched += scf_stats_p[i].n_resched;
 		scfs.n_single += scf_stats_p[i].n_single;
 		scfs.n_single_ofl += scf_stats_p[i].n_single_ofl;
+		scfs.n_single_rpc += scf_stats_p[i].n_single_rpc;
 		scfs.n_single_wait += scf_stats_p[i].n_single_wait;
 		scfs.n_single_wait_ofl += scf_stats_p[i].n_single_wait_ofl;
 		scfs.n_many += scf_stats_p[i].n_many;
@@ -168,9 +177,10 @@ static void scf_torture_stats_print(void)
 	if (atomic_read(&n_errs) || atomic_read(&n_mb_in_errs) ||
 	    atomic_read(&n_mb_out_errs) || atomic_read(&n_alloc_errs))
 		bangstr = "!!! ";
-	pr_alert("%s %sscf_invoked_count %s: %lld resched: %lld single: %lld/%lld single_ofl: %lld/%lld many: %lld/%lld all: %lld/%lld ",
+	pr_alert("%s %sscf_invoked_count %s: %lld resched: %lld single: %lld/%lld single_ofl: %lld/%lld single_rpc: %lld single_rpc_ofl: %lld many: %lld/%lld all: %lld/%lld ",
 		 SCFTORT_FLAG, bangstr, isdone ? "VER" : "ver", invoked_count, scfs.n_resched,
 		 scfs.n_single, scfs.n_single_wait, scfs.n_single_ofl, scfs.n_single_wait_ofl,
+		 scfs.n_single_rpc, scfs.n_single_rpc_ofl,
 		 scfs.n_many, scfs.n_many_wait, scfs.n_all, scfs.n_all_wait);
 	torture_onoff_stats();
 	pr_cont("ste: %d stnmie: %d stnmoe: %d staf: %d\n", atomic_read(&n_errs),
@@ -282,10 +292,13 @@ static void scf_handler(void *scfc_in)
 out:
 	if (unlikely(!scfcp))
 		return;
-	if (scfcp->scfc_wait)
+	if (scfcp->scfc_wait) {
 		WRITE_ONCE(scfcp->scfc_out, true);
-	else
+		if (scfcp->scfc_rpc)
+			complete(&scfcp->scfc_completion);
+	} else {
 		kfree(scfcp);
+	}
 }
 
 // As above, but check for correct CPU.
@@ -319,6 +332,7 @@ static void scftorture_invoke_one(struct scf_statistics *scfp, struct torture_ra
 			scfcp->scfc_cpu = -1;
 			scfcp->scfc_wait = scfsp->scfs_wait;
 			scfcp->scfc_out = false;
+			scfcp->scfc_rpc = false;
 		}
 	}
 	switch (scfsp->scfs_prim) {
@@ -350,6 +364,34 @@ static void scftorture_invoke_one(struct scf_statistics *scfp, struct torture_ra
 			scfcp = NULL;
 		}
 		break;
+	case SCF_PRIM_SINGLE_RPC:
+		if (!scfcp)
+			break;
+		cpu = torture_random(trsp) % nr_cpu_ids;
+		scfp->n_single_rpc++;
+		scfcp->scfc_cpu = cpu;
+		scfcp->scfc_wait = true;
+		init_completion(&scfcp->scfc_completion);
+		scfcp->scfc_rpc = true;
+		barrier(); // Prevent race-reduction compiler optimizations.
+		scfcp->scfc_in = true;
+		ret = smp_call_function_single(cpu, scf_handler_1, (void *)scfcp, 0);
+		if (!ret) {
+			if (use_cpus_read_lock)
+				cpus_read_unlock();
+			else
+				preempt_enable();
+			wait_for_completion(&scfcp->scfc_completion);
+			if (use_cpus_read_lock)
+				cpus_read_lock();
+			else
+				preempt_disable();
+		} else {
+			scfp->n_single_rpc_ofl++;
+			kfree(scfcp);
+			scfcp = NULL;
+		}
+		break;
 	case SCF_PRIM_MANY:
 		if (scfsp->scfs_wait)
 			scfp->n_many_wait++;
@@ -379,10 +421,12 @@ static void scftorture_invoke_one(struct scf_statistics *scfp, struct torture_ra
 	}
 	if (scfcp && scfsp->scfs_wait) {
 		if (WARN_ON_ONCE((num_online_cpus() > 1 || scfsp->scfs_prim == SCF_PRIM_SINGLE) &&
-				 !scfcp->scfc_out))
+				 !scfcp->scfc_out)) {
+			pr_warn("%s: Memory-ordering failure, scfs_prim: %d.\n", __func__, scfsp->scfs_prim);
 			atomic_inc(&n_mb_out_errs); // Leak rather than trash!
-		else
+		} else {
 			kfree(scfcp);
+		}
 		barrier(); // Prevent race-reduction compiler optimizations.
 	}
 	if (use_cpus_read_lock)
@@ -453,8 +497,8 @@ static void
 scftorture_print_module_parms(const char *tag)
 {
 	pr_alert(SCFTORT_FLAG
-		 "--- %s:  verbose=%d holdoff=%d longwait=%d nthreads=%d onoff_holdoff=%d onoff_interval=%d shutdown_secs=%d stat_interval=%d stutter=%d use_cpus_read_lock=%d, weight_resched=%d, weight_single=%d, weight_single_wait=%d, weight_many=%d, weight_many_wait=%d, weight_all=%d, weight_all_wait=%d\n", tag,
-		 verbose, holdoff, longwait, nthreads, onoff_holdoff, onoff_interval, shutdown, stat_interval, stutter, use_cpus_read_lock, weight_resched, weight_single, weight_single_wait, weight_many, weight_many_wait, weight_all, weight_all_wait);
+		 "--- %s:  verbose=%d holdoff=%d longwait=%d nthreads=%d onoff_holdoff=%d onoff_interval=%d shutdown_secs=%d stat_interval=%d stutter=%d use_cpus_read_lock=%d, weight_resched=%d, weight_single=%d, weight_single_rpc=%d, weight_single_wait=%d, weight_many=%d, weight_many_wait=%d, weight_all=%d, weight_all_wait=%d\n", tag,
+		 verbose, holdoff, longwait, nthreads, onoff_holdoff, onoff_interval, shutdown, stat_interval, stutter, use_cpus_read_lock, weight_resched, weight_single, weight_single_rpc, weight_single_wait, weight_many, weight_many_wait, weight_all, weight_all_wait);
 }
 
 static void scf_cleanup_handler(void *unused)
@@ -497,6 +541,7 @@ static int __init scf_torture_init(void)
 	int firsterr = 0;
 	unsigned long weight_resched1 = weight_resched;
 	unsigned long weight_single1 = weight_single;
+	unsigned long weight_single_rpc1 = weight_single_rpc;
 	unsigned long weight_single_wait1 = weight_single_wait;
 	unsigned long weight_many1 = weight_many;
 	unsigned long weight_many_wait1 = weight_many_wait;
@@ -508,11 +553,13 @@ static int __init scf_torture_init(void)
 
 	scftorture_print_module_parms("Start of test");
 
-	if (weight_resched == -1 && weight_single == -1 && weight_single_wait == -1 &&
+	if (weight_resched == -1 &&
+	    weight_single == -1 && weight_single_rpc == -1 && weight_single_wait == -1 &&
 	    weight_many == -1 && weight_many_wait == -1 &&
 	    weight_all == -1 && weight_all_wait == -1) {
 		weight_resched1 = 2 * nr_cpu_ids;
 		weight_single1 = 2 * nr_cpu_ids;
+		weight_single_rpc1 = 2 * nr_cpu_ids;
 		weight_single_wait1 = 2 * nr_cpu_ids;
 		weight_many1 = 2;
 		weight_many_wait1 = 2;
@@ -523,6 +570,8 @@ static int __init scf_torture_init(void)
 			weight_resched1 = 0;
 		if (weight_single == -1)
 			weight_single1 = 0;
+		if (weight_single_rpc == -1)
+			weight_single_rpc1 = 0;
 		if (weight_single_wait == -1)
 			weight_single_wait1 = 0;
 		if (weight_many == -1)
@@ -534,7 +583,7 @@ static int __init scf_torture_init(void)
 		if (weight_all_wait == -1)
 			weight_all_wait1 = 0;
 	}
-	if (weight_single1 == 0 && weight_single_wait1 == 0 &&
+	if (weight_single1 == 0 && weight_single_rpc1 == 0 && weight_single_wait1 == 0 &&
 	    weight_many1 == 0 && weight_many_wait1 == 0 &&
 	    weight_all1 == 0 && weight_all_wait1 == 0) {
 		VERBOSE_SCFTORTOUT_ERRSTRING("all zero weights makes no sense");
@@ -546,6 +595,7 @@ static int __init scf_torture_init(void)
 	else if (weight_resched1)
 		VERBOSE_SCFTORTOUT_ERRSTRING("built as module, weight_resched ignored");
 	scf_sel_add(weight_single1, SCF_PRIM_SINGLE, false);
+	scf_sel_add(weight_single_rpc1, SCF_PRIM_SINGLE_RPC, true);
 	scf_sel_add(weight_single_wait1, SCF_PRIM_SINGLE, true);
 	scf_sel_add(weight_many1, SCF_PRIM_MANY, false);
 	scf_sel_add(weight_many_wait1, SCF_PRIM_MANY, true);
-- 
2.31.1.189.g2e36527f23

[PATCH rcu 7/7] scftorture: Avoid NULL pointer exception on early exit

[Paul E. McKenney]

When scftorture finds an error in the module parameters controlling
the relative frequencies of smp_call_function*() variants, it takes an
early exit.  So early that it has not allocated memory to track the
kthreads running the test, which results in a segfault.  This commit
therefore checks for the existence of the memory before attempting
to stop the kthreads that would otherwise have been recorded in that
non-existent memory.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/scftorture.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/scftorture.c b/kernel/scftorture.c
index 5cf40e4383191..64a08288b1a6d 100644
--- a/kernel/scftorture.c
+++ b/kernel/scftorture.c
@@ -513,7 +513,7 @@ static void scf_torture_cleanup(void)
 		return;
 
 	WRITE_ONCE(scfdone, true);
-	if (nthreads)
+	if (nthreads && scf_stats_p)
 		for (i = 0; i < nthreads; i++)
 			torture_stop_kthread("scftorture_invoker", scf_stats_p[i].task);
 	else
-- 
2.31.1.189.g2e36527f23

[PATCH v2 rcu 1/7] refscale: Add measurement of clock readout

[Paul E. McKenney]

This commit adds a "clock" type to refscale, which checks the performance
of ktime_get_real_fast_ns().  Use the "clocksource=" kernel boot parameter
to select the underlying clock source.

[ paulmck: Work around compiler false positive per kernel test robot. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
index d998a76fb5422..66dc14cf5687e 100644
--- a/kernel/rcu/refscale.c
+++ b/kernel/rcu/refscale.c
@@ -467,6 +467,40 @@ static struct ref_scale_ops acqrel_ops = {
 	.name		= "acqrel"
 };
 
+static volatile u64 stopopts;
+
+static void ref_clock_section(const int nloops)
+{
+	u64 x = 0;
+	int i;
+
+	preempt_disable();
+	for (i = nloops; i >= 0; i--)
+		x += ktime_get_real_fast_ns();
+	preempt_enable();
+	stopopts = x;
+}
+
+static void ref_clock_delay_section(const int nloops, const int udl, const int ndl)
+{
+	u64 x = 0;
+	int i;
+
+	preempt_disable();
+	for (i = nloops; i >= 0; i--) {
+		x += ktime_get_real_fast_ns();
+		un_delay(udl, ndl);
+	}
+	preempt_enable();
+	stopopts = x;
+}
+
+static struct ref_scale_ops clock_ops = {
+	.readsection	= ref_clock_section,
+	.delaysection	= ref_clock_delay_section,
+	.name		= "clock"
+};
+
 static void rcu_scale_one_reader(void)
 {
 	if (readdelay <= 0)
@@ -759,7 +793,7 @@ ref_scale_init(void)
 	int firsterr = 0;
 	static struct ref_scale_ops *scale_ops[] = {
 		&rcu_ops, &srcu_ops, &rcu_trace_ops, &rcu_tasks_ops, &refcnt_ops, &rwlock_ops,
-		&rwsem_ops, &lock_ops, &lock_irq_ops, &acqrel_ops,
+		&rwsem_ops, &lock_ops, &lock_irq_ops, &acqrel_ops, &clock_ops,
 	};
 
 	if (!torture_init_begin(scale_type, verbose))