[PATCH v4 0/2] My new rcutorture patches for 6.15

[PATCH v4 0/2] My new rcutorture patches for 6.15

[Joel Fernandes]

The gpwrap one is is v4 where I just fixed the hrtimer_init() since v2.

The ARM64 image check is now in my for-next branch, it is required to do large
scale tests with SRCU.

(These are only the new commits, the existing ones in my for-next branch for
rcutorture will be sent separately once we figure out which one of them is
causing SRCU issues).

Joel Fernandes (2):
  rcutorture: Perform more frequent testing of ->gpwrap
  rcutorture: Fix issue with re-using old images on ARM64

 kernel/rcu/rcu.h                              |  4 ++
 kernel/rcu/rcutorture.c                       | 68 ++++++++++++++++++-
 kernel/rcu/tree.c                             | 34 +++++++++-
 kernel/rcu/tree.h                             |  1 +
 .../rcutorture/bin/kvm-test-1-run.sh          |  2 +-
 6 files changed, 107 insertions(+), 6 deletions(-)

-- 
2.43.0

[PATCH v4 1/2] rcutorture: Perform more frequent testing of ->gpwrap

[Joel Fernandes]

Currently, the ->gpwrap is not tested (at all per my testing) due to the
requirement of a large delta between a CPU's rdp->gp_seq and its node's
rnp->gpseq.

This results in no testing of ->gpwrap being set. This patch by default
adds 5 minutes of testing with ->gpwrap forced by lowering the delta
between rdp->gp_seq and rnp->gp_seq to just 8 GPs. All of this is
configurable, including the active time for the setting and a full
testing cycle.

By default, the first 25 minutes of a test will have the _default_
behavior there is right now (ULONG_MAX / 4) delta. Then for 5 minutes,
we switch to a smaller delta causing 1-2 wraps in 5 minutes. I believe
this is reasonable since we at least add a little bit of testing for
usecases where ->gpwrap is set.

Tested-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
---
 kernel/rcu/rcu.h        |  4 +++
 kernel/rcu/rcutorture.c | 67 ++++++++++++++++++++++++++++++++++++++++-
 kernel/rcu/tree.c       | 34 +++++++++++++++++++--
 kernel/rcu/tree.h       |  1 +
 4 files changed, 103 insertions(+), 3 deletions(-)

diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index eed2951a4962..516b26024a37 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -572,6 +572,8 @@ void do_trace_rcu_torture_read(const char *rcutorturename,
 			       unsigned long c_old,
 			       unsigned long c);
 void rcu_gp_set_torture_wait(int duration);
+void rcu_set_gpwrap_lag(unsigned long lag);
+int rcu_get_gpwrap_count(int cpu);
 #else
 static inline void rcutorture_get_gp_data(int *flags, unsigned long *gp_seq)
 {
@@ -589,6 +591,8 @@ void do_trace_rcu_torture_read(const char *rcutorturename,
 	do { } while (0)
 #endif
 static inline void rcu_gp_set_torture_wait(int duration) { }
+static inline void rcu_set_gpwrap_lag(unsigned long lag) { }
+static inline int rcu_get_gpwrap_count(int cpu) { return 0; }
 #endif
 unsigned long long rcutorture_gather_gp_seqs(void);
 void rcutorture_format_gp_seqs(unsigned long long seqs, char *cp, size_t len);
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 4fa7772be183..74de92c3a9ab 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -115,6 +115,9 @@ torture_param(int, nreaders, -1, "Number of RCU reader threads");
 torture_param(int, object_debug, 0, "Enable debug-object double call_rcu() testing");
 torture_param(int, onoff_holdoff, 0, "Time after boot before CPU hotplugs (s)");
 torture_param(int, onoff_interval, 0, "Time between CPU hotplugs (jiffies), 0=disable");
+torture_param(int, gpwrap_lag_cycle_mins, 30, "Total cycle duration for ovf lag testing (in minutes)");
+torture_param(int, gpwrap_lag_active_mins, 5, "Duration for which ovf lag is active within each cycle (in minutes)");
+torture_param(int, gpwrap_lag_gps, 8, "Value to set for set_gpwrap_lag during an active testing period.");
 torture_param(int, nocbs_nthreads, 0, "Number of NOCB toggle threads, 0 to disable");
 torture_param(int, nocbs_toggle, 1000, "Time between toggling nocb state (ms)");
 torture_param(int, preempt_duration, 0, "Preemption duration (ms), zero to disable");
@@ -413,6 +416,8 @@ struct rcu_torture_ops {
 	bool (*reader_blocked)(void);
 	unsigned long long (*gather_gp_seqs)(void);
 	void (*format_gp_seqs)(unsigned long long seqs, char *cp, size_t len);
+	void (*set_gpwrap_lag)(unsigned long lag);
+	int (*get_gpwrap_count)(int cpu);
 	long cbflood_max;
 	int irq_capable;
 	int can_boost;
@@ -619,6 +624,8 @@ static struct rcu_torture_ops rcu_ops = {
 				  : NULL,
 	.gather_gp_seqs		= rcutorture_gather_gp_seqs,
 	.format_gp_seqs		= rcutorture_format_gp_seqs,
+	.set_gpwrap_lag		= rcu_set_gpwrap_lag,
+	.get_gpwrap_count	= rcu_get_gpwrap_count,
 	.irq_capable		= 1,
 	.can_boost		= IS_ENABLED(CONFIG_RCU_BOOST),
 	.extendables		= RCUTORTURE_MAX_EXTEND,
@@ -2394,6 +2401,7 @@ rcu_torture_stats_print(void)
 	int i;
 	long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
 	long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
+	long n_gpwraps = 0;
 	struct rcu_torture *rtcp;
 	static unsigned long rtcv_snap = ULONG_MAX;
 	static bool splatted;
@@ -2404,6 +2412,7 @@ rcu_torture_stats_print(void)
 			pipesummary[i] += READ_ONCE(per_cpu(rcu_torture_count, cpu)[i]);
 			batchsummary[i] += READ_ONCE(per_cpu(rcu_torture_batch, cpu)[i]);
 		}
+		n_gpwraps += cur_ops->get_gpwrap_count(cpu);
 	}
 	for (i = RCU_TORTURE_PIPE_LEN; i >= 0; i--) {
 		if (pipesummary[i] != 0)
@@ -2435,8 +2444,9 @@ rcu_torture_stats_print(void)
 		data_race(n_barrier_attempts),
 		data_race(n_rcu_torture_barrier_error));
 	pr_cont("read-exits: %ld ", data_race(n_read_exits)); // Statistic.
-	pr_cont("nocb-toggles: %ld:%ld\n",
+	pr_cont("nocb-toggles: %ld:%ld ",
 		atomic_long_read(&n_nocb_offload), atomic_long_read(&n_nocb_deoffload));
+	pr_cont("gpwraps: %ld\n", n_gpwraps);
 
 	pr_alert("%s%s ", torture_type, TORTURE_FLAG);
 	if (atomic_read(&n_rcu_torture_mberror) ||
@@ -3607,6 +3617,54 @@ static int rcu_torture_preempt(void *unused)
 
 static enum cpuhp_state rcutor_hp;
 
+static struct hrtimer gpwrap_lag_timer;
+static bool gpwrap_lag_active;
+
+/* Timer handler for toggling RCU grace-period sequence overflow test lag value */
+static enum hrtimer_restart rcu_gpwrap_lag_timer(struct hrtimer *timer)
+{
+	ktime_t next_delay;
+
+	if (gpwrap_lag_active) {
+		pr_alert("rcu-torture: Disabling ovf lag (value=0)\n");
+		cur_ops->set_gpwrap_lag(0);
+		gpwrap_lag_active = false;
+		next_delay = ktime_set((gpwrap_lag_cycle_mins - gpwrap_lag_active_mins) * 60, 0);
+	} else {
+		pr_alert("rcu-torture: Enabling ovf lag (value=%d)\n", gpwrap_lag_gps);
+		cur_ops->set_gpwrap_lag(gpwrap_lag_gps);
+		gpwrap_lag_active = true;
+		next_delay = ktime_set(gpwrap_lag_active_mins * 60, 0);
+	}
+
+	if (torture_must_stop())
+		return HRTIMER_NORESTART;
+
+	hrtimer_forward_now(timer, next_delay);
+	return HRTIMER_RESTART;
+}
+
+static int rcu_gpwrap_lag_init(void)
+{
+	if (gpwrap_lag_cycle_mins <= 0 || gpwrap_lag_active_mins <= 0) {
+		pr_alert("rcu-torture: lag timing parameters must be positive\n");
+		return -EINVAL;
+	}
+
+	hrtimer_setup(&gpwrap_lag_timer, rcu_gpwrap_lag_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+	gpwrap_lag_active = false;
+	hrtimer_start(&gpwrap_lag_timer,
+		      ktime_set((gpwrap_lag_cycle_mins - gpwrap_lag_active_mins) * 60, 0), HRTIMER_MODE_REL);
+
+	return 0;
+}
+
+static void rcu_gpwrap_lag_cleanup(void)
+{
+	hrtimer_cancel(&gpwrap_lag_timer);
+	cur_ops->set_gpwrap_lag(0);
+	gpwrap_lag_active = false;
+}
 static void
 rcu_torture_cleanup(void)
 {
@@ -3776,6 +3834,9 @@ rcu_torture_cleanup(void)
 	torture_cleanup_end();
 	if (cur_ops->gp_slow_unregister)
 		cur_ops->gp_slow_unregister(NULL);
+
+	if (cur_ops->set_gpwrap_lag)
+		rcu_gpwrap_lag_cleanup();
 }
 
 static void rcu_torture_leak_cb(struct rcu_head *rhp)
@@ -4275,6 +4336,10 @@ rcu_torture_init(void)
 	torture_init_end();
 	if (cur_ops->gp_slow_register && !WARN_ON_ONCE(!cur_ops->gp_slow_unregister))
 		cur_ops->gp_slow_register(&rcu_fwd_cb_nodelay);
+
+	if (cur_ops->set_gpwrap_lag && rcu_gpwrap_lag_init())
+		goto unwind;
+
 	return 0;
 
 unwind:
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 659f83e71048..6ec30d07759d 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -80,6 +80,15 @@ static void rcu_sr_normal_gp_cleanup_work(struct work_struct *);
 static DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, rcu_data) = {
 	.gpwrap = true,
 };
+
+int rcu_get_gpwrap_count(int cpu)
+{
+	struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
+
+	return READ_ONCE(rdp->gpwrap_count);
+}
+EXPORT_SYMBOL_GPL(rcu_get_gpwrap_count);
+
 static struct rcu_state rcu_state = {
 	.level = { &rcu_state.node[0] },
 	.gp_state = RCU_GP_IDLE,
@@ -757,6 +766,25 @@ void rcu_request_urgent_qs_task(struct task_struct *t)
 	smp_store_release(per_cpu_ptr(&rcu_data.rcu_urgent_qs, cpu), true);
 }
 
+/**
+ * rcu_set_gpwrap_lag - Set RCU GP sequence overflow lag value.
+ * @lag_gps: Set overflow lag to this many grace period worth of counters
+ * which is used by rcutorture to quickly force a gpwrap situation.
+ * @lag_gps = 0 means we reset it back to the boot-time value.
+ */
+static unsigned long seq_gpwrap_lag = ULONG_MAX / 4;
+
+void rcu_set_gpwrap_lag(unsigned long lag_gps)
+{
+	unsigned long lag_seq_count;
+
+	lag_seq_count = (lag_gps == 0)
+			? ULONG_MAX / 4
+			: lag_gps << RCU_SEQ_CTR_SHIFT;
+	WRITE_ONCE(seq_gpwrap_lag, lag_seq_count);
+}
+EXPORT_SYMBOL_GPL(rcu_set_gpwrap_lag);
+
 /*
  * When trying to report a quiescent state on behalf of some other CPU,
  * it is our responsibility to check for and handle potential overflow
@@ -767,9 +795,11 @@ void rcu_request_urgent_qs_task(struct task_struct *t)
 static void rcu_gpnum_ovf(struct rcu_node *rnp, struct rcu_data *rdp)
 {
 	raw_lockdep_assert_held_rcu_node(rnp);
-	if (ULONG_CMP_LT(rcu_seq_current(&rdp->gp_seq) + ULONG_MAX / 4,
-			 rnp->gp_seq))
+	if (ULONG_CMP_LT(rcu_seq_current(&rdp->gp_seq) + seq_gpwrap_lag,
+			 rnp->gp_seq)) {
 		WRITE_ONCE(rdp->gpwrap, true);
+		WRITE_ONCE(rdp->gpwrap_count, READ_ONCE(rdp->gpwrap_count) + 1);
+	}
 	if (ULONG_CMP_LT(rdp->rcu_iw_gp_seq + ULONG_MAX / 4, rnp->gp_seq))
 		rdp->rcu_iw_gp_seq = rnp->gp_seq + ULONG_MAX / 4;
 }
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index a9a811d9d7a3..63bea388c243 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -183,6 +183,7 @@ struct rcu_data {
 	bool		core_needs_qs;	/* Core waits for quiescent state. */
 	bool		beenonline;	/* CPU online at least once. */
 	bool		gpwrap;		/* Possible ->gp_seq wrap. */
+	unsigned int	gpwrap_count;	/* Count of GP sequence wrap. */
 	bool		cpu_started;	/* RCU watching this onlining CPU. */
 	struct rcu_node *mynode;	/* This CPU's leaf of hierarchy */
 	unsigned long grpmask;		/* Mask to apply to leaf qsmask. */
-- 
2.43.0

[PATCH v4 2/2] rcutorture: Fix issue with re-using old images on ARM64

[Joel Fernandes]

On ARM64, when running with --configs '36*SRCU-P', I noticed that only 1 instance
instead of 36 for starting.

Fix it by checking for Image files, instead of bzImage which ARM does
not seem to have. With this I see all 36 instances running at the same
time in the batch.

Tested-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
---
 kernel/rcu/rcutorture.c                                  | 3 ++-
 tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 74de92c3a9ab..df6504a855aa 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -2412,7 +2412,8 @@ rcu_torture_stats_print(void)
 			pipesummary[i] += READ_ONCE(per_cpu(rcu_torture_count, cpu)[i]);
 			batchsummary[i] += READ_ONCE(per_cpu(rcu_torture_batch, cpu)[i]);
 		}
-		n_gpwraps += cur_ops->get_gpwrap_count(cpu);
+		if (cur_ops->get_gpwrap_count)
+			n_gpwraps += cur_ops->get_gpwrap_count(cpu);
 	}
 	for (i = RCU_TORTURE_PIPE_LEN; i >= 0; i--) {
 		if (pipesummary[i] != 0)
diff --git a/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh b/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
index ad79784e552d..957800c9ffba 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
@@ -73,7 +73,7 @@ config_override_param "$config_dir/CFcommon.$(uname -m)" KcList \
 cp $T/KcList $resdir/ConfigFragment
 
 base_resdir=`echo $resdir | sed -e 's/\.[0-9]\+$//'`
-if test "$base_resdir" != "$resdir" && test -f $base_resdir/bzImage && test -f $base_resdir/vmlinux
+if test "$base_resdir" != "$resdir" && (test -f $base_resdir/bzImage || test -f $base_resdir/Image) && test -f $base_resdir/vmlinux
 then
 	# Rerunning previous test, so use that test's kernel.
 	QEMU="`identify_qemu $base_resdir/vmlinux`"
-- 
2.43.0

Re: [PATCH v4 0/2] My new rcutorture patches for 6.15

[Joel Fernandes]

On 4/15/2025 9:36 AM, Joel Fernandes wrote:
> The gpwrap one is is v4 where I just fixed the hrtimer_init() since v2.
> 
> The ARM64 image check is now in my for-next branch, it is required to do large
> scale tests with SRCU.
> 
> (These are only the new commits, the existing ones in my for-next branch for
> rcutorture will be sent separately once we figure out which one of them is
> causing SRCU issues).
> 
> Joel Fernandes (2):
>   rcutorture: Perform more frequent testing of ->gpwrap
>   rcutorture: Fix issue with re-using old images on ARM64
> 
>  kernel/rcu/rcu.h                              |  4 ++
>  kernel/rcu/rcutorture.c                       | 68 ++++++++++++++++++-
>  kernel/rcu/tree.c                             | 34 +++++++++-
>  kernel/rcu/tree.h                             |  1 +
>  .../rcutorture/bin/kvm-test-1-run.sh          |  2 +-
>  6 files changed, 107 insertions(+), 6 deletions(-)
> 

Oops, s/15/16/ in subject :)

 - Joel

Re: [PATCH v4 2/2] rcutorture: Fix issue with re-using old images on ARM64

[Joel Fernandes]

On 4/15/2025 9:36 AM, Joel Fernandes wrote:
> On ARM64, when running with --configs '36*SRCU-P', I noticed that only 1 instance
> instead of 36 for starting.
> 
> Fix it by checking for Image files, instead of bzImage which ARM does
> not seem to have. With this I see all 36 instances running at the same
> time in the batch.
> 
> Tested-by: Paul E. McKenney <paulmck@kernel.org>
> Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
> ---
>  kernel/rcu/rcutorture.c                                  | 3 ++-
>  tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh | 2 +-
>  2 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
> index 74de92c3a9ab..df6504a855aa 100644
> --- a/kernel/rcu/rcutorture.c
> +++ b/kernel/rcu/rcutorture.c
> @@ -2412,7 +2412,8 @@ rcu_torture_stats_print(void)
>  			pipesummary[i] += READ_ONCE(per_cpu(rcu_torture_count, cpu)[i]);
>  			batchsummary[i] += READ_ONCE(per_cpu(rcu_torture_batch, cpu)[i]);
>  		}
> -		n_gpwraps += cur_ops->get_gpwrap_count(cpu);
> +		if (cur_ops->get_gpwrap_count)
> +			n_gpwraps += cur_ops->get_gpwrap_count(cpu);
>  	}
Oops, this hunk was supposed to go into the previous patch. I fixed it in my
tree and will post with the full set of torture patches later:

https://git.kernel.org/pub/scm/linux/kernel/git/jfern/linux.git/log/?h=rcu/torture-for-6.16

Thanks.