[PATCH 0/4] Torture-test updates for v7.2

[PATCH 0/4] Torture-test updates for v7.2

[Paul E. McKenney]

Hello!

This series contains torture-test updates for v7.2:

1.	Fully test lazy RCU.

2.	Add torture_sched_set_normal() for user-specified nice values.

3.	Improve kvm-series.sh header comment.

4.	Allow "norm" abbreviation for "normal".

						Thanx, Paul

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

 b/include/linux/torture.h                              |    1 
 b/kernel/rcu/rcu.h                                     |    7 
 b/kernel/rcu/rcutorture.c                              |   21 +-
 b/kernel/rcu/tree_plugin.h                             |   32 +++
 b/kernel/torture.c                                     |   16 +
 b/tools/testing/selftests/rcutorture/bin/kvm-series.sh |   11 -
 b/tools/testing/selftests/rcutorture/bin/torture.sh    |    2 
 kernel/rcu/rcutorture.c                                |  160 +++++++++--------
 8 files changed, 168 insertions(+), 82 deletions(-)

[PATCH 1/6] rcutorture: Fully test lazy RCU

[Paul E. McKenney]

Currently, rcutorture bypasses lazy RCU by using call_rcu_hurry().
This works, avoiding the dreaded rtort_pipe_count WARN(), but fails to
fully test lazy RCU.  The rtort_pipe_count WARN() splats because lazy RCU
could delay the start of an RCU grace period for a full stutter period,
which defaults to only three seconds.

This commit therefore reverts the call_rcu_hurry() instances
back to call_rcu(), but, in kernels built with CONFIG_RCU_LAZY=y,
queues a workqueue handler just before the call to stutter_wait() in
rcu_torture_writer().  This workqueue handler invokes rcu_barrier(),
which motivates any lingering lazy callbacks, thus avoiding the splat.

Questions for review:

1.	Should we avoid queueing work for RCU implementations not
	supporting lazy callbacks?

2.	Should we avoid queueing work in kernels built with
	CONFIG_RCU_LAZY=y, but that were not booted with the
	rcutree.enable_rcu_lazy kernel boot parameter set?  (Note that
	this requires some ugliness to access this parameter, and must
	also handle Tiny RCU.)

3.	Does the rcu_torture_ops structure need a ->call_hurry() field,
	and if so, why?  If not, why not?

4.	Your additional questions here!

Reported-by: Saravana Kannan <saravanak@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/rcutorture.c | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 590fd0138589b8..3c8e4cd5b83e60 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -572,7 +572,7 @@ static unsigned long rcu_no_completed(void)
 
 static void rcu_torture_deferred_free(struct rcu_torture *p)
 {
-	call_rcu_hurry(&p->rtort_rcu, rcu_torture_cb);
+	call_rcu(&p->rtort_rcu, rcu_torture_cb);
 }
 
 static void rcu_sync_torture_init(void)
@@ -619,7 +619,7 @@ static struct rcu_torture_ops rcu_ops = {
 	.poll_gp_state_exp	= poll_state_synchronize_rcu,
 	.cond_sync_exp		= cond_synchronize_rcu_expedited,
 	.cond_sync_exp_full	= cond_synchronize_rcu_expedited_full,
-	.call			= call_rcu_hurry,
+	.call			= call_rcu,
 	.cb_barrier		= rcu_barrier,
 	.fqs			= rcu_force_quiescent_state,
 	.gp_kthread_dbg		= show_rcu_gp_kthreads,
@@ -1145,7 +1145,7 @@ static void rcu_tasks_torture_deferred_free(struct rcu_torture *p)
 
 static void synchronize_rcu_mult_test(void)
 {
-	synchronize_rcu_mult(call_rcu_tasks, call_rcu_hurry);
+	synchronize_rcu_mult(call_rcu_tasks, call_rcu);
 }
 
 static struct rcu_torture_ops tasks_ops = {
@@ -1631,6 +1631,17 @@ static void do_rtws_sync(struct torture_random_state *trsp, void (*sync)(void))
 		cpus_read_unlock();
 }
 
+/*
+ * Do an rcu_barrier() to motivate lazy callbacks during a stutter
+ * pause.  Without this, we can get false-positives rtort_pipe_count
+ * splats.
+ */
+static void rcu_torture_writer_work(struct work_struct *work)
+{
+	if (cur_ops->cb_barrier)
+		cur_ops->cb_barrier();
+}
+
 /*
  * RCU torture writer kthread.  Repeatedly substitutes a new structure
  * for that pointed to by rcu_torture_current, freeing the old structure
@@ -1651,6 +1662,7 @@ rcu_torture_writer(void *arg)
 	int i;
 	int idx;
 	unsigned long j;
+	struct work_struct lazy_work;
 	int oldnice = task_nice(current);
 	struct rcu_gp_oldstate *rgo = NULL;
 	int rgo_size = 0;
@@ -1667,6 +1679,7 @@ rcu_torture_writer(void *arg)
 		stallsdone += (stall_cpu_holdoff + stall_gp_kthread + stall_cpu + 60) *
 			      HZ * (stall_cpu_repeat + 1);
 	VERBOSE_TOROUT_STRING("rcu_torture_writer task started");
+	INIT_WORK_ONSTACK(&lazy_work, rcu_torture_writer_work);
 	if (!can_expedite)
 		pr_alert("%s" TORTURE_FLAG
 			 " GP expediting controlled from boot/sysfs for %s.\n",
@@ -1895,6 +1908,8 @@ rcu_torture_writer(void *arg)
 				       !rcu_gp_is_normal();
 		}
 		rcu_torture_writer_state = RTWS_STUTTER;
+		if (IS_ENABLED(CONFIG_RCU_LAZY))
+			queue_work(system_percpu_wq, &lazy_work);
 		stutter_waited = stutter_wait("rcu_torture_writer");
 		if (stutter_waited &&
 		    !atomic_read(&rcu_fwd_cb_nodelay) &&
-- 
2.40.1

[PATCH 2/6] torture: Add torture_sched_set_normal() for user-specified nice values

[Paul E. McKenney]

This new torture_sched_set_normal() function clamps the nice value at
the MIN_NICE..MAX_NICE limits, splatting it these limits are exceeded.
It then invokes sched_set_normal() to set the new value.  This prevents
more difficult-to-debug failures within the scheduler.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 include/linux/torture.h |  1 +
 kernel/torture.c        | 16 ++++++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/include/linux/torture.h b/include/linux/torture.h
index d80f24ff69e3e1..66d2d444428aef 100644
--- a/include/linux/torture.h
+++ b/include/linux/torture.h
@@ -129,6 +129,7 @@ void _torture_stop_kthread(char *m, struct task_struct **tp);
 #else
 #define torture_preempt_schedule()	do { } while (0)
 #endif
+void torture_sched_set_normal(struct task_struct *t, int nice);
 
 #if IS_ENABLED(CONFIG_RCU_TORTURE_TEST) || IS_ENABLED(CONFIG_LOCK_TORTURE_TEST) || IS_ENABLED(CONFIG_HAZPTR_TORTURE_TEST)
 long torture_sched_setaffinity(pid_t pid, const struct cpumask *in_mask, bool dowarn);
diff --git a/kernel/torture.c b/kernel/torture.c
index 62c1ac77769424..77cb3589b19f9c 100644
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -972,3 +972,19 @@ void _torture_stop_kthread(char *m, struct task_struct **tp)
 	*tp = NULL;
 }
 EXPORT_SYMBOL_GPL(_torture_stop_kthread);
+
+/*
+ * Set the specified task's niceness value, saturating at limits.
+ * Saturating noisily, but saturating.
+ */
+void torture_sched_set_normal(struct task_struct *t, int nice)
+{
+	int realnice = nice;
+
+	if (WARN_ON_ONCE(realnice > MAX_NICE))
+		realnice = MAX_NICE;
+	if (WARN_ON_ONCE(realnice < MIN_NICE))
+		realnice = MIN_NICE;
+	sched_set_normal(t, realnice);
+}
+EXPORT_SYMBOL_GPL(torture_sched_set_normal);
-- 
2.40.1

[PATCH 3/6] torture: Improve kvm-series.sh header comment

[Paul E. McKenney]

The constraints on the arguments to kvm-series.sh are easy to forget,
so this commit adds examples in the header comment.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 tools/testing/selftests/rcutorture/bin/kvm-series.sh | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/rcutorture/bin/kvm-series.sh b/tools/testing/selftests/rcutorture/bin/kvm-series.sh
index c4ee5f9109310e..be9412538fb8e7 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm-series.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm-series.sh
@@ -1,12 +1,13 @@
 #!/bin/bash
 # SPDX-License-Identifier: GPL-2.0+
 #
-# Usage: kvm-series.sh config-list commit-id-list [ kvm.sh parameters ]
+# Usage: kvm-series.sh config-list commit-id-range [ kvm.sh parameters ]
 #
-# Tests the specified list of unadorned configs ("TREE01 SRCU-P" but not
-# "CFLIST" or "3*TRACE01") and an indication of a set of commits to test,
-# then runs each commit through the specified list of commits using kvm.sh.
-# The runs are grouped into a -series/config/commit directory tree.
+# Tests the specified list of unadorned configs ("TREE01 SRCU-P" but
+# not "CFLIST" or "3*TRACE01") and an indication of a range of commits
+# ("v7.0-rc1..rcu/dev", but not "cd0ce7bab0408 ff74db28df623 17c52d7b31a1f")
+# to test, then runs each commit through the specified list of commits using
+# kvm.sh.  The runs are grouped into a -series/config/commit directory tree.
 # Each run defaults to a duration of one minute.
 #
 # Run in top-level Linux source directory.  Please note that this is in
-- 
2.40.1

[PATCH 4/6] torture: Allow "norm" abbreviation for "normal"

[Paul E. McKenney]

This adds "--do-norm", --do-no-norm", and "--no-norm" synonyms for the
"--do-normal" group of torture.sh command-line arguments.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 tools/testing/selftests/rcutorture/bin/torture.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/rcutorture/bin/torture.sh b/tools/testing/selftests/rcutorture/bin/torture.sh
index a33ba109ef0b7f..f0083891ee8147 100755
--- a/tools/testing/selftests/rcutorture/bin/torture.sh
+++ b/tools/testing/selftests/rcutorture/bin/torture.sh
@@ -184,7 +184,7 @@ do
 		do_clocksourcewd=no
 		do_srcu_lockdep=no
 		;;
-	--do-normal|--do-no-normal|--no-normal)
+	--do-normal|--do-norm|--do-no-normal|--do-no-norm|--no-normal|--no-norm)
 		do_normal=`doyesno "$1" --do-normal`
 		explicit_normal=yes
 		;;
-- 
2.40.1

Re: [PATCH 0/4] Torture-test updates for v7.2

[Uladzislau Rezki]

On Thu, May 07, 2026 at 09:57:11AM -0700, Paul E. McKenney wrote:
> Hello!
> 
> This series contains torture-test updates for v7.2:
> 
> 1.	Fully test lazy RCU.
> 
> 2.	Add torture_sched_set_normal() for user-specified nice values.
> 
> 3.	Improve kvm-series.sh header comment.
> 
> 4.	Allow "norm" abbreviation for "normal".
> 
> 						Thanx, Paul
> 
> ------------------------------------------------------------------------
> 
>  b/include/linux/torture.h                              |    1 
>  b/kernel/rcu/rcu.h                                     |    7 
>  b/kernel/rcu/rcutorture.c                              |   21 +-
>  b/kernel/rcu/tree_plugin.h                             |   32 +++
>  b/kernel/torture.c                                     |   16 +
>  b/tools/testing/selftests/rcutorture/bin/kvm-series.sh |   11 -
>  b/tools/testing/selftests/rcutorture/bin/torture.sh    |    2 
>  kernel/rcu/rcutorture.c                                |  160 +++++++++--------
>  8 files changed, 168 insertions(+), 82 deletions(-)
> 
This i took.

--
Uladzislau Rezki