[PATCH rcu 0/11] Torture-test updates

[PATCH rcu 0/11] Torture-test updates

[Paul E. McKenney]

Hello!

This series contains torture-test updates:

1.	Add get_torture_init_jiffies() for test-start time.

2.	Add a test_boost_holdoff module parameter.

3.	Include grace-period sequence numbers in failure/close-call.

4.	Expand failure/close-call grace-period output.

5.	Trace expedited grace-period numbers in hexadecimal.

6.	Add ftrace-compatible timestamp to GP# failure/close-call output.

7.	Make cur_ops->format_gp_seqs take buffer length.

8.	Move RCU_TORTURE_TEST_{CHK_RDR_STATE,LOG_CPU} to bool.

9.	Complain when invalid SRCU reader_flavor is specified.

10.	Add FORCE_NEED_SRCU_NMI_SAFE Kconfig for testing.

11.	Make SRCU lockdep testing use srcu_read_lock_nmisafe().

						Thanx, Paul

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

 b/Documentation/admin-guide/kernel-parameters.txt        |    5 +
 b/include/linux/torture.h                                |    1 
 b/include/trace/events/rcu.h                             |    2 
 b/kernel/rcu/Kconfig                                     |   11 ++
 b/kernel/rcu/Kconfig.debug                               |   14 +++
 b/kernel/rcu/rcu.h                                       |    2 
 b/kernel/rcu/rcutorture.c                                |   19 +++-
 b/kernel/rcu/tiny.c                                      |   14 +++
 b/kernel/rcu/tree.c                                      |   20 ++++
 b/kernel/torture.c                                       |   12 ++
 b/tools/testing/selftests/rcutorture/bin/srcu_lockdep.sh |    2 
 kernel/rcu/Kconfig.debug                                 |    4 
 kernel/rcu/rcu.h                                         |    6 -
 kernel/rcu/rcutorture.c                                  |   64 ++++++++++++---
 kernel/rcu/tiny.c                                        |   12 +-
 kernel/rcu/tree.c                                        |   22 ++---
 16 files changed, 173 insertions(+), 37 deletions(-)

[PATCH rcu 01/11] torture: Add get_torture_init_jiffies() for test-start time

[Paul E. McKenney]

This commit adds a get_torture_init_jiffies() function that returns the
value of the jiffies counter at the start of the test, that is, at the
point where torture_init_begin() was invoked.

This will be used to enable torture-test holdoffs for tests implemented
using per-CPU kthreads, which are created and deleted by CPU-hotplug
operations, and thus (unlike normal kthreads) don't automatically know
when the test started.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 include/linux/torture.h |  1 +
 kernel/torture.c        | 12 ++++++++++++
 2 files changed, 13 insertions(+)

diff --git a/include/linux/torture.h b/include/linux/torture.h
index 0134e7221cae6..1b59056c3b182 100644
--- a/include/linux/torture.h
+++ b/include/linux/torture.h
@@ -104,6 +104,7 @@ int torture_stutter_init(int s, int sgap);
 /* Initialization and cleanup. */
 bool torture_init_begin(char *ttype, int v);
 void torture_init_end(void);
+unsigned long get_torture_init_jiffies(void);
 bool torture_cleanup_begin(void);
 void torture_cleanup_end(void);
 bool torture_must_stop(void);
diff --git a/kernel/torture.c b/kernel/torture.c
index dede150aef011..3a0a8cc604010 100644
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -792,6 +792,8 @@ static void torture_stutter_cleanup(void)
 	stutter_task = NULL;
 }
 
+static unsigned long torture_init_jiffies;
+
 static void
 torture_print_module_parms(void)
 {
@@ -821,6 +823,7 @@ bool torture_init_begin(char *ttype, int v)
 	torture_type = ttype;
 	verbose = v;
 	fullstop = FULLSTOP_DONTSTOP;
+	WRITE_ONCE(torture_init_jiffies, jiffies); // Lockless reads.
 	torture_print_module_parms();
 	return true;
 }
@@ -836,6 +839,15 @@ void torture_init_end(void)
 }
 EXPORT_SYMBOL_GPL(torture_init_end);
 
+/*
+ * Get the torture_init_begin()-time value of the jiffies counter.
+ */
+unsigned long get_torture_init_jiffies(void)
+{
+	return READ_ONCE(torture_init_jiffies);
+}
+EXPORT_SYMBOL_GPL(get_torture_init_jiffies);
+
 /*
  * Clean up torture module.  Please note that this is -not- invoked via
  * the usual module_exit() mechanism, but rather by an explicit call from
-- 
2.40.1

[PATCH rcu 02/11] rcutorture: Add a test_boost_holdoff module parameter

[Paul E. McKenney]

This commit adds a test_boost_holdoff module parameter that tells the RCU
priority-boosting tests to wait for the specified number of seconds past
the start of the rcutorture test.  This can be useful when rcutorture
is built into the kernel (as opposed to being modprobed), especially on
large systems where early start of RCU priority boosting can delay the
boot sequence, which adds a full CPU's worth of load onto the system.
This can in turn result in pointless stall warnings.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 .../admin-guide/kernel-parameters.txt         |  5 +++++
 kernel/rcu/rcutorture.c                       | 19 ++++++++++++++++---
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 3152f2c1da294..d6c3f9d9d3a73 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -5592,6 +5592,11 @@
 	rcutorture.test_boost_duration= [KNL]
 			Duration (s) of each individual boost test.
 
+	rcutorture.test_boost_holdoff= [KNL]
+			Holdoff time (s) from start of test to the start
+			of RCU priority-boost testing.	Defaults to zero,
+			that is, no holdoff.
+
 	rcutorture.test_boost_interval= [KNL]
 			Interval (s) between each boost test.
 
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 1bd3eaa0b8e7a..9788933984655 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -135,6 +135,7 @@ torture_param(int, stat_interval, 60, "Number of seconds between stats printk()s
 torture_param(int, stutter, 5, "Number of seconds to run/halt test");
 torture_param(int, test_boost, 1, "Test RCU prio boost: 0=no, 1=maybe, 2=yes.");
 torture_param(int, test_boost_duration, 4, "Duration of each boost test, seconds.");
+torture_param(int, test_boost_holdoff, 0, "Holdoff time from rcutorture start, seconds.");
 torture_param(int, test_boost_interval, 7, "Interval between boost tests, seconds.");
 torture_param(int, test_nmis, 0, "End-test NMI tests, 0 to disable.");
 torture_param(bool, test_no_idle_hz, true, "Test support for tickless idle CPUs");
@@ -1159,8 +1160,19 @@ static int rcu_torture_boost(void *arg)
 	unsigned long gp_state;
 	unsigned long gp_state_time;
 	unsigned long oldstarttime;
+	unsigned long booststarttime = get_torture_init_jiffies() + test_boost_holdoff * HZ;
 
-	VERBOSE_TOROUT_STRING("rcu_torture_boost started");
+	if (test_boost_holdoff <= 0 || time_after(jiffies, booststarttime)) {
+		VERBOSE_TOROUT_STRING("rcu_torture_boost started");
+	} else {
+		VERBOSE_TOROUT_STRING("rcu_torture_boost started holdoff period");
+		while (time_before(jiffies, booststarttime)) {
+			schedule_timeout_idle(HZ);
+			if (kthread_should_stop())
+				goto cleanup;
+		}
+		VERBOSE_TOROUT_STRING("rcu_torture_boost finished holdoff period");
+	}
 
 	/* Set real-time priority. */
 	sched_set_fifo_low(current);
@@ -1236,6 +1248,7 @@ checkwait:	if (stutter_wait("rcu_torture_boost"))
 			sched_set_fifo_low(current);
 	} while (!torture_must_stop());
 
+cleanup:
 	/* Clean up and exit. */
 	while (!kthread_should_stop()) {
 		torture_shutdown_absorb("rcu_torture_boost");
@@ -2523,7 +2536,7 @@ rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, const char *tag)
 		 "shuffle_interval=%d stutter=%d irqreader=%d "
 		 "fqs_duration=%d fqs_holdoff=%d fqs_stutter=%d "
 		 "test_boost=%d/%d test_boost_interval=%d "
-		 "test_boost_duration=%d shutdown_secs=%d "
+		 "test_boost_duration=%d test_boost_holdoff=%d shutdown_secs=%d "
 		 "stall_cpu=%d stall_cpu_holdoff=%d stall_cpu_irqsoff=%d "
 		 "stall_cpu_block=%d stall_cpu_repeat=%d "
 		 "n_barrier_cbs=%d "
@@ -2537,7 +2550,7 @@ rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, const char *tag)
 		 stat_interval, verbose, test_no_idle_hz, shuffle_interval,
 		 stutter, irqreader, fqs_duration, fqs_holdoff, fqs_stutter,
 		 test_boost, cur_ops->can_boost,
-		 test_boost_interval, test_boost_duration, shutdown_secs,
+		 test_boost_interval, test_boost_duration, test_boost_holdoff, shutdown_secs,
 		 stall_cpu, stall_cpu_holdoff, stall_cpu_irqsoff,
 		 stall_cpu_block, stall_cpu_repeat,
 		 n_barrier_cbs,
-- 
2.40.1

[PATCH rcu 03/11] rcutorture: Include grace-period sequence numbers in failure/close-call

[Paul E. McKenney]

This commit includes the grace-period sequence numbers at the beginning
and end of each segment in the "Failure/close-call rcutorture reader
segments" list.  These are in hexadecimal, and only the bottom byte.
Currently, only RCU is supported, with its three sequence numbers (normal,
expedited, and polled).

Note that if all the grace-period sequence numbers remain the same across
a given reader segement, only one copy of the number will be printed.
Of course, if there is a change, both sets of values will be printed.

Because the overhead of collecting this information can suppress
heisenbugs, this information is collected and printed only in kernels
built with CONFIG_RCU_TORTURE_TEST_LOG_GP=y.

[ paulmck: Apply Nathan Chancellor feedback for IS_ENABLED(). ]
[ paulmck: Apply feedback from kernel test robot. ]

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: kernel test robot <oliver.sang@intel.com>
---
 kernel/rcu/Kconfig.debug | 14 ++++++++++++++
 kernel/rcu/rcu.h         |  2 ++
 kernel/rcu/rcutorture.c  | 34 ++++++++++++++++++++++++++++++++++
 kernel/rcu/tiny.c        | 14 ++++++++++++++
 kernel/rcu/tree.c        | 20 ++++++++++++++++++++
 5 files changed, 84 insertions(+)

diff --git a/kernel/rcu/Kconfig.debug b/kernel/rcu/Kconfig.debug
index 6af90510a1ca7..25a9dc2be0dcd 100644
--- a/kernel/rcu/Kconfig.debug
+++ b/kernel/rcu/Kconfig.debug
@@ -84,6 +84,20 @@ config RCU_TORTURE_TEST_LOG_CPU
 	  Say Y here if you want CPU IDs logged.
 	  Say N if you are unsure.
 
+config RCU_TORTURE_TEST_LOG_GP
+	bool "Log grace-period numbers for rcutorture failures"
+	depends on RCU_TORTURE_TEST
+	default n
+	help
+	  This option causes rcutorture to decorate each entry of its
+	  log of failure/close-call rcutorture reader segments with the
+	  corresponding grace-period sequence numbers.	This information
+	  can be useful, but it does incur additional overhead, overhead
+	  that can make both failures and close calls less probable.
+
+	  Say Y here if you want grace-period sequence numbers logged.
+	  Say N if you are unsure.
+
 config RCU_REF_SCALE_TEST
 	tristate "Scalability tests for read-side synchronization (RCU and others)"
 	depends on DEBUG_KERNEL
diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index f6fcf87d91395..7c14eec7c13ae 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -590,6 +590,8 @@ void do_trace_rcu_torture_read(const char *rcutorturename,
 #endif
 static inline void rcu_gp_set_torture_wait(int duration) { }
 #endif
+unsigned long rcutorture_gather_gp_seqs(void);
+void rcutorture_format_gp_seqs(unsigned long seqs, char *cp);
 
 #ifdef CONFIG_TINY_SRCU
 
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 9788933984655..7af7de1688466 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -273,6 +273,8 @@ struct rt_read_seg {
 	bool rt_preempted;
 	int rt_cpu;
 	int rt_end_cpu;
+	unsigned long rt_gp_seq;
+	unsigned long rt_gp_seq_end;
 };
 static int err_segs_recorded;
 static struct rt_read_seg err_segs[RCUTORTURE_RDR_MAX_SEGS];
@@ -407,6 +409,8 @@ struct rcu_torture_ops {
 	void (*gp_slow_register)(atomic_t *rgssp);
 	void (*gp_slow_unregister)(atomic_t *rgssp);
 	bool (*reader_blocked)(void);
+	unsigned long (*gather_gp_seqs)(void);
+	void (*format_gp_seqs)(unsigned long seqs, char *cp);
 	long cbflood_max;
 	int irq_capable;
 	int can_boost;
@@ -611,6 +615,8 @@ static struct rcu_torture_ops rcu_ops = {
 	.reader_blocked		= IS_ENABLED(CONFIG_RCU_TORTURE_TEST_LOG_CPU)
 				  ? has_rcu_reader_blocked
 				  : NULL,
+	.gather_gp_seqs		= rcutorture_gather_gp_seqs,
+	.format_gp_seqs		= rcutorture_format_gp_seqs,
 	.irq_capable		= 1,
 	.can_boost		= IS_ENABLED(CONFIG_RCU_BOOST),
 	.extendables		= RCUTORTURE_MAX_EXTEND,
@@ -656,6 +662,8 @@ static struct rcu_torture_ops rcu_busted_ops = {
 	.sync		= synchronize_rcu_busted,
 	.exp_sync	= synchronize_rcu_busted,
 	.call		= call_rcu_busted,
+	.gather_gp_seqs	= rcutorture_gather_gp_seqs,
+	.format_gp_seqs	= rcutorture_format_gp_seqs,
 	.irq_capable	= 1,
 	.extendables	= RCUTORTURE_MAX_EXTEND,
 	.name		= "busted"
@@ -1989,6 +1997,12 @@ static void rcutorture_one_extend(int *readstate, int newstate, bool insoftirq,
 				rtrsp[-1].rt_preempted = cur_ops->reader_blocked();
 		}
 	}
+	// Sample grace-period sequence number, as good a place as any.
+	if (IS_ENABLED(CONFIG_RCU_TORTURE_TEST_LOG_GP) && cur_ops->gather_gp_seqs) {
+		rtrsp->rt_gp_seq = cur_ops->gather_gp_seqs();
+		if (!first)
+			rtrsp[-1].rt_gp_seq_end = rtrsp->rt_gp_seq;
+	}
 
 	/*
 	 * Next, remove old protection, in decreasing order of strength
@@ -3577,6 +3591,7 @@ rcu_torture_cleanup(void)
 	int flags = 0;
 	unsigned long gp_seq = 0;
 	int i;
+	int j;
 
 	if (torture_cleanup_begin()) {
 		if (cur_ops->cb_barrier != NULL) {
@@ -3672,6 +3687,25 @@ rcu_torture_cleanup(void)
 				else
 					pr_cont(" ...");
 			}
+			if (IS_ENABLED(CONFIG_RCU_TORTURE_TEST_LOG_GP) &&
+			    cur_ops->gather_gp_seqs && cur_ops->format_gp_seqs) {
+				char buf1[16+1];
+				char buf2[16+1];
+				char sepchar = '-';
+
+				cur_ops->format_gp_seqs(err_segs[i].rt_gp_seq, buf1);
+				cur_ops->format_gp_seqs(err_segs[i].rt_gp_seq_end, buf2);
+				if (err_segs[i].rt_gp_seq == err_segs[i].rt_gp_seq_end) {
+					if (buf2[0]) {
+						for (j = 0; buf2[j]; j++)
+							buf2[j] = '.';
+						if (j)
+							buf2[j - 1] = ' ';
+					}
+					sepchar = ' ';
+				}
+				pr_cont(" %s%c%s", buf1, sepchar, buf2);
+			}
 			if (err_segs[i].rt_delay_ms != 0) {
 				pr_cont(" %s%ldms", firsttime ? "" : "+",
 					err_segs[i].rt_delay_ms);
diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
index b3b3ce34df631..773944257e796 100644
--- a/kernel/rcu/tiny.c
+++ b/kernel/rcu/tiny.c
@@ -257,6 +257,20 @@ void kvfree_call_rcu(struct rcu_head *head, void *ptr)
 EXPORT_SYMBOL_GPL(kvfree_call_rcu);
 #endif
 
+#if IS_ENABLED(CONFIG_RCU_TORTURE_TEST)
+unsigned long rcutorture_gather_gp_seqs(void)
+{
+	return READ_ONCE(rcu_ctrlblk.gp_seq) & 0xff;
+}
+EXPORT_SYMBOL_GPL(rcutorture_gather_gp_seqs);
+
+void rcutorture_format_gp_seqs(unsigned long seqs, char *cp)
+{
+	snprintf(cp, 8, "g%02lx", seqs & 0xff);
+}
+EXPORT_SYMBOL_GPL(rcutorture_format_gp_seqs);
+#endif
+
 void __init rcu_init(void)
 {
 	open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 9ba34206e20d2..574a280660624 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -559,6 +559,26 @@ void rcutorture_get_gp_data(int *flags, unsigned long *gp_seq)
 }
 EXPORT_SYMBOL_GPL(rcutorture_get_gp_data);
 
+/* Gather grace-period sequence numbers for rcutorture diagnostics. */
+unsigned long rcutorture_gather_gp_seqs(void)
+{
+	return ((READ_ONCE(rcu_state.gp_seq) & 0xff) << 16) |
+	       ((READ_ONCE(rcu_state.expedited_sequence) & 0xff) << 8) |
+	       (READ_ONCE(rcu_state.gp_seq_polled) & 0xff);
+}
+EXPORT_SYMBOL_GPL(rcutorture_gather_gp_seqs);
+
+/* Format grace-period sequence numbers for rcutorture diagnostics. */
+void rcutorture_format_gp_seqs(unsigned long seqs, char *cp)
+{
+	unsigned int egp = (seqs >> 8) & 0xff;
+	unsigned int ggp = (seqs >> 16) & 0xff;
+	unsigned int pgp = seqs & 0xff;
+
+	snprintf(cp, 16, "g%02x:e%02x:p%02x", ggp, egp, pgp);
+}
+EXPORT_SYMBOL_GPL(rcutorture_format_gp_seqs);
+
 #if defined(CONFIG_NO_HZ_FULL) && (!defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_KVM_XFER_TO_GUEST_WORK))
 /*
  * An empty function that will trigger a reschedule on
-- 
2.40.1

[PATCH rcu 04/11] rcutorture: Expand failure/close-call grace-period output

[Paul E. McKenney]

With only eight bits per grace-period sequence number, wrap can happen
in 64 grace periods.  This commit therefore increases this to sixteen
bits for normal grace-period sequence numbers and the combined short-form
polling sequence numbers, thus deferring wrap for at least 16,384 grace
periods.  Because expedited grace periods go faster, expand these to 24
bits, deferring wrap for at least 4,194,304 expedited grace periods.
These longer wrap times makes it easier to correlate these numbers to
trace-event output.

Note that the low-order two bits are reserved for intra-grace-period
state, hence the above wrap numbers being a factor of four smaller than
you might expect.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/rcu.h        |  4 ++--
 kernel/rcu/rcutorture.c | 12 ++++++------
 kernel/rcu/tiny.c       |  8 ++++----
 kernel/rcu/tree.c       | 18 +++++++++---------
 4 files changed, 21 insertions(+), 21 deletions(-)

diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index 7c14eec7c13ae..d2a91f705a4ab 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -590,8 +590,8 @@ void do_trace_rcu_torture_read(const char *rcutorturename,
 #endif
 static inline void rcu_gp_set_torture_wait(int duration) { }
 #endif
-unsigned long rcutorture_gather_gp_seqs(void);
-void rcutorture_format_gp_seqs(unsigned long seqs, char *cp);
+unsigned long long rcutorture_gather_gp_seqs(void);
+void rcutorture_format_gp_seqs(unsigned long long seqs, char *cp);
 
 #ifdef CONFIG_TINY_SRCU
 
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 7af7de1688466..5b0510c79fde7 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -273,8 +273,8 @@ struct rt_read_seg {
 	bool rt_preempted;
 	int rt_cpu;
 	int rt_end_cpu;
-	unsigned long rt_gp_seq;
-	unsigned long rt_gp_seq_end;
+	unsigned long long rt_gp_seq;
+	unsigned long long rt_gp_seq_end;
 };
 static int err_segs_recorded;
 static struct rt_read_seg err_segs[RCUTORTURE_RDR_MAX_SEGS];
@@ -409,8 +409,8 @@ struct rcu_torture_ops {
 	void (*gp_slow_register)(atomic_t *rgssp);
 	void (*gp_slow_unregister)(atomic_t *rgssp);
 	bool (*reader_blocked)(void);
-	unsigned long (*gather_gp_seqs)(void);
-	void (*format_gp_seqs)(unsigned long seqs, char *cp);
+	unsigned long long (*gather_gp_seqs)(void);
+	void (*format_gp_seqs)(unsigned long long seqs, char *cp);
 	long cbflood_max;
 	int irq_capable;
 	int can_boost;
@@ -3689,8 +3689,8 @@ rcu_torture_cleanup(void)
 			}
 			if (IS_ENABLED(CONFIG_RCU_TORTURE_TEST_LOG_GP) &&
 			    cur_ops->gather_gp_seqs && cur_ops->format_gp_seqs) {
-				char buf1[16+1];
-				char buf2[16+1];
+				char buf1[20+1];
+				char buf2[20+1];
 				char sepchar = '-';
 
 				cur_ops->format_gp_seqs(err_segs[i].rt_gp_seq, buf1);
diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
index 773944257e796..b97c64e99a905 100644
--- a/kernel/rcu/tiny.c
+++ b/kernel/rcu/tiny.c
@@ -258,15 +258,15 @@ EXPORT_SYMBOL_GPL(kvfree_call_rcu);
 #endif
 
 #if IS_ENABLED(CONFIG_RCU_TORTURE_TEST)
-unsigned long rcutorture_gather_gp_seqs(void)
+unsigned long long rcutorture_gather_gp_seqs(void)
 {
-	return READ_ONCE(rcu_ctrlblk.gp_seq) & 0xff;
+	return READ_ONCE(rcu_ctrlblk.gp_seq) & 0xffffULL;
 }
 EXPORT_SYMBOL_GPL(rcutorture_gather_gp_seqs);
 
-void rcutorture_format_gp_seqs(unsigned long seqs, char *cp)
+void rcutorture_format_gp_seqs(unsigned long long seqs, char *cp)
 {
-	snprintf(cp, 8, "g%02lx", seqs & 0xff);
+	snprintf(cp, 8, "g%04llx", seqs & 0xffffULL);
 }
 EXPORT_SYMBOL_GPL(rcutorture_format_gp_seqs);
 #endif
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 574a280660624..ac596596e7717 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -560,22 +560,22 @@ void rcutorture_get_gp_data(int *flags, unsigned long *gp_seq)
 EXPORT_SYMBOL_GPL(rcutorture_get_gp_data);
 
 /* Gather grace-period sequence numbers for rcutorture diagnostics. */
-unsigned long rcutorture_gather_gp_seqs(void)
+unsigned long long rcutorture_gather_gp_seqs(void)
 {
-	return ((READ_ONCE(rcu_state.gp_seq) & 0xff) << 16) |
-	       ((READ_ONCE(rcu_state.expedited_sequence) & 0xff) << 8) |
-	       (READ_ONCE(rcu_state.gp_seq_polled) & 0xff);
+	return ((READ_ONCE(rcu_state.gp_seq) & 0xffffULL) << 40) |
+	       ((READ_ONCE(rcu_state.expedited_sequence) & 0xffffffULL) << 16) |
+	       (READ_ONCE(rcu_state.gp_seq_polled) & 0xffffULL);
 }
 EXPORT_SYMBOL_GPL(rcutorture_gather_gp_seqs);
 
 /* Format grace-period sequence numbers for rcutorture diagnostics. */
-void rcutorture_format_gp_seqs(unsigned long seqs, char *cp)
+void rcutorture_format_gp_seqs(unsigned long long seqs, char *cp)
 {
-	unsigned int egp = (seqs >> 8) & 0xff;
-	unsigned int ggp = (seqs >> 16) & 0xff;
-	unsigned int pgp = seqs & 0xff;
+	unsigned int egp = (seqs >> 16) & 0xffffffULL;
+	unsigned int ggp = (seqs >> 40) & 0xffffULL;
+	unsigned int pgp = seqs & 0xffffULL;
 
-	snprintf(cp, 16, "g%02x:e%02x:p%02x", ggp, egp, pgp);
+	snprintf(cp, 20, "g%04x:e%06x:p%04x", ggp, egp, pgp);
 }
 EXPORT_SYMBOL_GPL(rcutorture_format_gp_seqs);
 
-- 
2.40.1

[PATCH rcu 05/11] rcu: Trace expedited grace-period numbers in hexadecimal

[Paul E. McKenney]

This commit reformats the expedited grace-period numbers into hexadecimal
for easier decoding and comparison.  The normal grace-period numbers
remain in decimal for the time being.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 include/trace/events/rcu.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
index e81431deaa50b..63fd8aa99af7c 100644
--- a/include/trace/events/rcu.h
+++ b/include/trace/events/rcu.h
@@ -207,7 +207,7 @@ TRACE_EVENT_RCU(rcu_exp_grace_period,
 		__entry->gpevent = gpevent;
 	),
 
-	TP_printk("%s %ld %s",
+	TP_printk("%s %#lx %s",
 		  __entry->rcuname, __entry->gpseq, __entry->gpevent)
 );
 
-- 
2.40.1

[PATCH rcu 06/11] rcutorture: Add ftrace-compatible timestamp to GP# failure/close-call output

[Paul E. McKenney]

This commit adds an ftrace-compatible microsecond-scale timestamp
to the failure/close-call output, but only in kernels built with
CONFIG_RCU_TORTURE_TEST_LOG_GP=y.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/rcutorture.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 5b0510c79fde7..0f5a945427190 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -275,6 +275,7 @@ struct rt_read_seg {
 	int rt_end_cpu;
 	unsigned long long rt_gp_seq;
 	unsigned long long rt_gp_seq_end;
+	u64 rt_ts;
 };
 static int err_segs_recorded;
 static struct rt_read_seg err_segs[RCUTORTURE_RDR_MAX_SEGS];
@@ -2000,6 +2001,7 @@ static void rcutorture_one_extend(int *readstate, int newstate, bool insoftirq,
 	// Sample grace-period sequence number, as good a place as any.
 	if (IS_ENABLED(CONFIG_RCU_TORTURE_TEST_LOG_GP) && cur_ops->gather_gp_seqs) {
 		rtrsp->rt_gp_seq = cur_ops->gather_gp_seqs();
+		rtrsp->rt_ts = ktime_get_mono_fast_ns();
 		if (!first)
 			rtrsp[-1].rt_gp_seq_end = rtrsp->rt_gp_seq;
 	}
@@ -3674,7 +3676,11 @@ rcu_torture_cleanup(void)
 			pr_alert("\t: No segments recorded!!!\n");
 		firsttime = 1;
 		for (i = 0; i < rt_read_nsegs; i++) {
-			pr_alert("\t%d: %#4x", i, err_segs[i].rt_readstate);
+			if (IS_ENABLED(CONFIG_RCU_TORTURE_TEST_LOG_GP))
+				pr_alert("\t%lluus ", div64_u64(err_segs[i].rt_ts, 1000ULL));
+			else
+				pr_alert("\t");
+			pr_cont("%d: %#4x", i, err_segs[i].rt_readstate);
 			if (err_segs[i].rt_delay_jiffies != 0) {
 				pr_cont("%s%ldjiffies", firsttime ? "" : "+",
 					err_segs[i].rt_delay_jiffies);
-- 
2.40.1

[PATCH rcu 07/11] rcutorture: Make cur_ops->format_gp_seqs take buffer length

[Paul E. McKenney]

The Tree and Tiny implementations of rcutorture_format_gp_seqs() use
hard-coded constants for the length of the buffer that they format into.
This is of course an accident waiting to happen, so this commit therefore
makes them take a length argument.  The rcutorture calling code uses
ARRAY_SIZE() to safely compute this new argument.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/rcu.h        | 2 +-
 kernel/rcu/rcutorture.c | 8 +++++---
 kernel/rcu/tiny.c       | 4 ++--
 kernel/rcu/tree.c       | 4 ++--
 4 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index d2a91f705a4ab..eed2951a4962d 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -591,7 +591,7 @@ void do_trace_rcu_torture_read(const char *rcutorturename,
 static inline void rcu_gp_set_torture_wait(int duration) { }
 #endif
 unsigned long long rcutorture_gather_gp_seqs(void);
-void rcutorture_format_gp_seqs(unsigned long long seqs, char *cp);
+void rcutorture_format_gp_seqs(unsigned long long seqs, char *cp, size_t len);
 
 #ifdef CONFIG_TINY_SRCU
 
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 0f5a945427190..2e6e8664e4038 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -411,7 +411,7 @@ struct rcu_torture_ops {
 	void (*gp_slow_unregister)(atomic_t *rgssp);
 	bool (*reader_blocked)(void);
 	unsigned long long (*gather_gp_seqs)(void);
-	void (*format_gp_seqs)(unsigned long long seqs, char *cp);
+	void (*format_gp_seqs)(unsigned long long seqs, char *cp, size_t len);
 	long cbflood_max;
 	int irq_capable;
 	int can_boost;
@@ -3699,8 +3699,10 @@ rcu_torture_cleanup(void)
 				char buf2[20+1];
 				char sepchar = '-';
 
-				cur_ops->format_gp_seqs(err_segs[i].rt_gp_seq, buf1);
-				cur_ops->format_gp_seqs(err_segs[i].rt_gp_seq_end, buf2);
+				cur_ops->format_gp_seqs(err_segs[i].rt_gp_seq,
+							buf1, ARRAY_SIZE(buf1));
+				cur_ops->format_gp_seqs(err_segs[i].rt_gp_seq_end,
+							buf2, ARRAY_SIZE(buf2));
 				if (err_segs[i].rt_gp_seq == err_segs[i].rt_gp_seq_end) {
 					if (buf2[0]) {
 						for (j = 0; buf2[j]; j++)
diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
index b97c64e99a905..6380fbd27557a 100644
--- a/kernel/rcu/tiny.c
+++ b/kernel/rcu/tiny.c
@@ -264,9 +264,9 @@ unsigned long long rcutorture_gather_gp_seqs(void)
 }
 EXPORT_SYMBOL_GPL(rcutorture_gather_gp_seqs);
 
-void rcutorture_format_gp_seqs(unsigned long long seqs, char *cp)
+void rcutorture_format_gp_seqs(unsigned long long seqs, char *cp, size_t len)
 {
-	snprintf(cp, 8, "g%04llx", seqs & 0xffffULL);
+	snprintf(cp, len, "g%04llx", seqs & 0xffffULL);
 }
 EXPORT_SYMBOL_GPL(rcutorture_format_gp_seqs);
 #endif
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index ac596596e7717..1d201455aa7c3 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -569,13 +569,13 @@ unsigned long long rcutorture_gather_gp_seqs(void)
 EXPORT_SYMBOL_GPL(rcutorture_gather_gp_seqs);
 
 /* Format grace-period sequence numbers for rcutorture diagnostics. */
-void rcutorture_format_gp_seqs(unsigned long long seqs, char *cp)
+void rcutorture_format_gp_seqs(unsigned long long seqs, char *cp, size_t len)
 {
 	unsigned int egp = (seqs >> 16) & 0xffffffULL;
 	unsigned int ggp = (seqs >> 40) & 0xffffULL;
 	unsigned int pgp = seqs & 0xffffULL;
 
-	snprintf(cp, 20, "g%04x:e%06x:p%04x", ggp, egp, pgp);
+	snprintf(cp, len, "g%04x:e%06x:p%04x", ggp, egp, pgp);
 }
 EXPORT_SYMBOL_GPL(rcutorture_format_gp_seqs);
 
-- 
2.40.1

[PATCH rcu 08/11] rcutorture: Move RCU_TORTURE_TEST_{CHK_RDR_STATE,LOG_CPU} to bool

[Paul E. McKenney]

The RCU_TORTURE_TEST_CHK_RDR_STATE and RCU_TORTURE_TEST_LOG_CPU Kconfig
options are pointlessly defined as tristate.  This commit therefore
converts them to bool.

Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202412241458.150d082b-lkp@intel.com
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/Kconfig.debug | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/rcu/Kconfig.debug b/kernel/rcu/Kconfig.debug
index 25a9dc2be0dcd..12e4c64ebae15 100644
--- a/kernel/rcu/Kconfig.debug
+++ b/kernel/rcu/Kconfig.debug
@@ -54,7 +54,7 @@ config RCU_TORTURE_TEST
 	  Say N if you are unsure.
 
 config RCU_TORTURE_TEST_CHK_RDR_STATE
-	tristate "Check rcutorture reader state"
+	bool "Check rcutorture reader state"
 	depends on RCU_TORTURE_TEST
 	default n
 	help
@@ -70,7 +70,7 @@ config RCU_TORTURE_TEST_CHK_RDR_STATE
 	  Say N if you are unsure.
 
 config RCU_TORTURE_TEST_LOG_CPU
-	tristate "Log CPU for rcutorture failures"
+	bool "Log CPU for rcutorture failures"
 	depends on RCU_TORTURE_TEST
 	default n
 	help
-- 
2.40.1

[PATCH rcu 09/11] rcutorture: Complain when invalid SRCU reader_flavor is specified

[Paul E. McKenney]

Currently, rcutorture ignores reader_flavor bits that are not in the
SRCU_READ_FLAVOR_ALL bitmask, which could confuse rcutorture users into
believing buggy patches had been fully tested.  This commit therefore
produces a splat in this case.

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

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 2e6e8664e4038..36bc8d1332d43 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -690,6 +690,8 @@ static int srcu_torture_read_lock(void)
 	struct srcu_ctr __percpu *scp;
 	int ret = 0;
 
+	WARN_ON_ONCE(reader_flavor & ~SRCU_READ_FLAVOR_ALL);
+
 	if ((reader_flavor & SRCU_READ_FLAVOR_NORMAL) || !(reader_flavor & SRCU_READ_FLAVOR_ALL)) {
 		idx = srcu_read_lock(srcu_ctlp);
 		WARN_ON_ONCE(idx & ~0x1);
-- 
2.40.1

[PATCH rcu 10/11] srcu: Add FORCE_NEED_SRCU_NMI_SAFE Kconfig for testing

[Paul E. McKenney]

The srcu_read_lock_nmisafe() and srcu_read_unlock_nmisafe() functions
map to __srcu_read_lock() and __srcu_read_unlock() on systems like x86
that have NMI-safe this_cpu_inc() operations.  This makes the underlying
__srcu_read_lock_nmisafe() and __srcu_read_unlock_nmisafe() functions
difficult to test on (for example) x86 systems, allowing bugs to creep in.

This commit therefore creates a FORCE_NEED_SRCU_NMI_SAFE Kconfig that
forces those underlying functions to be used even on systems where they
are not needed, thus providing better testing coverage.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/Kconfig | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig
index 80242957fa417..aa42de4d27684 100644
--- a/kernel/rcu/Kconfig
+++ b/kernel/rcu/Kconfig
@@ -65,6 +65,17 @@ config TREE_SRCU
 	help
 	  This option selects the full-fledged version of SRCU.
 
+config FORCE_NEED_SRCU_NMI_SAFE
+	bool "Force selection of NEED_SRCU_NMI_SAFE"
+	depends on !TINY_SRCU
+	select NEED_SRCU_NMI_SAFE
+	default n
+	help
+	  This option forces selection of the NEED_SRCU_NMI_SAFE
+	  Kconfig option, allowing testing of srcu_read_lock_nmisafe()
+	  and srcu_read_unlock_nmisafe() on architectures (like x86)
+	  that select the ARCH_HAS_NMI_SAFE_THIS_CPU_OPS Kconfig option.
+
 config NEED_SRCU_NMI_SAFE
 	def_bool HAVE_NMI && !ARCH_HAS_NMI_SAFE_THIS_CPU_OPS && !TINY_SRCU
 
-- 
2.40.1

[PATCH rcu 11/11] torture: Make SRCU lockdep testing use srcu_read_lock_nmisafe()

[Paul E. McKenney]

Recent experience shows that the srcu_read_lock_nmisafe() and
srcu_read_unlock_nmisafe() functions are not sufficiently tested.
This commit therefore causes the torture.sh script's SRCU lockdep testing
to use these two functions.  This will cause these two functions to
be regularly tested by several developers (myself included) who use
torture.sh as an RCU acceptance test.

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

diff --git a/tools/testing/selftests/rcutorture/bin/srcu_lockdep.sh b/tools/testing/selftests/rcutorture/bin/srcu_lockdep.sh
index 2e63ef009d593..2db12c5cad9c6 100755
--- a/tools/testing/selftests/rcutorture/bin/srcu_lockdep.sh
+++ b/tools/testing/selftests/rcutorture/bin/srcu_lockdep.sh
@@ -49,7 +49,7 @@ do
 		do
 			err=
 			val=$((d*1000+t*10+c))
-			tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration 5s --configs "SRCU-P" --bootargs "rcutorture.test_srcu_lockdep=$val" --trust-make --datestamp "$ds/$val" > "$T/kvm.sh.out" 2>&1
+			tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration 5s --configs "SRCU-P" --kconfig "CONFIG_FORCE_NEED_SRCU_NMI_SAFE=y" --bootargs "rcutorture.test_srcu_lockdep=$val rcutorture.reader_flavor=0x2" --trust-make --datestamp "$ds/$val" > "$T/kvm.sh.out" 2>&1
 			ret=$?
 			mv "$T/kvm.sh.out" "$RCUTORTURE/res/$ds/$val"
 			if test "$d" -ne 0 && test "$ret" -eq 0
-- 
2.40.1

Re: [PATCH rcu 0/11] Torture-test updates

[Paul E. McKenney]

Hello!

This series contains torture-test updates:

1.	Add get_torture_init_jiffies() for test-start time.

2.	Add a test_boost_holdoff module parameter.

3.	Include grace-period sequence numbers in failure/close-call.

4.	Expand failure/close-call grace-period output.

5.	Trace expedited grace-period numbers in hexadecimal.

6.	Add ftrace-compatible timestamp to GP# failure/close-call output.

7.	Make cur_ops->format_gp_seqs take buffer length.

8.	Move RCU_TORTURE_TEST_{CHK_RDR_STATE,LOG_CPU} to bool.

9.	Complain when invalid SRCU reader_flavor is specified.

10.	Add FORCE_NEED_SRCU_NMI_SAFE Kconfig for testing.

11.	Make SRCU lockdep testing use srcu_read_lock_nmisafe().

Changes since v1:

o	Fix "segement" typo in commit log.

						Thanx, Paul

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

 b/Documentation/admin-guide/kernel-parameters.txt        |    5 +
 b/include/linux/torture.h                                |    1 
 b/include/trace/events/rcu.h                             |    2 
 b/kernel/rcu/Kconfig                                     |   11 ++
 b/kernel/rcu/Kconfig.debug                               |   14 +++
 b/kernel/rcu/rcu.h                                       |    2 
 b/kernel/rcu/rcutorture.c                                |   19 +++-
 b/kernel/rcu/tiny.c                                      |   14 +++
 b/kernel/rcu/tree.c                                      |   20 ++++
 b/kernel/torture.c                                       |   12 ++
 b/tools/testing/selftests/rcutorture/bin/srcu_lockdep.sh |    2 
 kernel/rcu/Kconfig.debug                                 |    4 
 kernel/rcu/rcu.h                                         |    6 -
 kernel/rcu/rcutorture.c                                  |   64 ++++++++++++---
 kernel/rcu/tiny.c                                        |   12 +-
 kernel/rcu/tree.c                                        |   22 ++---
 16 files changed, 173 insertions(+), 37 deletions(-)

[PATCH rcu v2] 01/11] torture: Add get_torture_init_jiffies() for test-start time

[Paul E. McKenney]

This commit adds a get_torture_init_jiffies() function that returns the
value of the jiffies counter at the start of the test, that is, at the
point where torture_init_begin() was invoked.

This will be used to enable torture-test holdoffs for tests implemented
using per-CPU kthreads, which are created and deleted by CPU-hotplug
operations, and thus (unlike normal kthreads) don't automatically know
when the test started.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 include/linux/torture.h |  1 +
 kernel/torture.c        | 12 ++++++++++++
 2 files changed, 13 insertions(+)

diff --git a/include/linux/torture.h b/include/linux/torture.h
index 0134e7221cae..1b59056c3b18 100644
--- a/include/linux/torture.h
+++ b/include/linux/torture.h
@@ -104,6 +104,7 @@ int torture_stutter_init(int s, int sgap);
 /* Initialization and cleanup. */
 bool torture_init_begin(char *ttype, int v);
 void torture_init_end(void);
+unsigned long get_torture_init_jiffies(void);
 bool torture_cleanup_begin(void);
 void torture_cleanup_end(void);
 bool torture_must_stop(void);
diff --git a/kernel/torture.c b/kernel/torture.c
index dede150aef01..3a0a8cc60401 100644
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -792,6 +792,8 @@ static void torture_stutter_cleanup(void)
 	stutter_task = NULL;
 }
 
+static unsigned long torture_init_jiffies;
+
 static void
 torture_print_module_parms(void)
 {
@@ -821,6 +823,7 @@ bool torture_init_begin(char *ttype, int v)
 	torture_type = ttype;
 	verbose = v;
 	fullstop = FULLSTOP_DONTSTOP;
+	WRITE_ONCE(torture_init_jiffies, jiffies); // Lockless reads.
 	torture_print_module_parms();
 	return true;
 }
@@ -836,6 +839,15 @@ void torture_init_end(void)
 }
 EXPORT_SYMBOL_GPL(torture_init_end);
 
+/*
+ * Get the torture_init_begin()-time value of the jiffies counter.
+ */
+unsigned long get_torture_init_jiffies(void)
+{
+	return READ_ONCE(torture_init_jiffies);
+}
+EXPORT_SYMBOL_GPL(get_torture_init_jiffies);
+
 /*
  * Clean up torture module.  Please note that this is -not- invoked via
  * the usual module_exit() mechanism, but rather by an explicit call from
-- 
2.40.1

[PATCH rcu v2] 02/11] rcutorture: Add a test_boost_holdoff module parameter

[Paul E. McKenney]

This commit adds a test_boost_holdoff module parameter that tells the RCU
priority-boosting tests to wait for the specified number of seconds past
the start of the rcutorture test.  This can be useful when rcutorture
is built into the kernel (as opposed to being modprobed), especially on
large systems where early start of RCU priority boosting can delay the
boot sequence, which adds a full CPU's worth of load onto the system.
This can in turn result in pointless stall warnings.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 .../admin-guide/kernel-parameters.txt         |  5 +++++
 kernel/rcu/rcutorture.c                       | 19 ++++++++++++++++---
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 3152f2c1da29..d6c3f9d9d3a7 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -5592,6 +5592,11 @@
 	rcutorture.test_boost_duration= [KNL]
 			Duration (s) of each individual boost test.
 
+	rcutorture.test_boost_holdoff= [KNL]
+			Holdoff time (s) from start of test to the start
+			of RCU priority-boost testing.	Defaults to zero,
+			that is, no holdoff.
+
 	rcutorture.test_boost_interval= [KNL]
 			Interval (s) between each boost test.
 
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 1bd3eaa0b8e7..978893398465 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -135,6 +135,7 @@ torture_param(int, stat_interval, 60, "Number of seconds between stats printk()s
 torture_param(int, stutter, 5, "Number of seconds to run/halt test");
 torture_param(int, test_boost, 1, "Test RCU prio boost: 0=no, 1=maybe, 2=yes.");
 torture_param(int, test_boost_duration, 4, "Duration of each boost test, seconds.");
+torture_param(int, test_boost_holdoff, 0, "Holdoff time from rcutorture start, seconds.");
 torture_param(int, test_boost_interval, 7, "Interval between boost tests, seconds.");
 torture_param(int, test_nmis, 0, "End-test NMI tests, 0 to disable.");
 torture_param(bool, test_no_idle_hz, true, "Test support for tickless idle CPUs");
@@ -1159,8 +1160,19 @@ static int rcu_torture_boost(void *arg)
 	unsigned long gp_state;
 	unsigned long gp_state_time;
 	unsigned long oldstarttime;
+	unsigned long booststarttime = get_torture_init_jiffies() + test_boost_holdoff * HZ;
 
-	VERBOSE_TOROUT_STRING("rcu_torture_boost started");
+	if (test_boost_holdoff <= 0 || time_after(jiffies, booststarttime)) {
+		VERBOSE_TOROUT_STRING("rcu_torture_boost started");
+	} else {
+		VERBOSE_TOROUT_STRING("rcu_torture_boost started holdoff period");
+		while (time_before(jiffies, booststarttime)) {
+			schedule_timeout_idle(HZ);
+			if (kthread_should_stop())
+				goto cleanup;
+		}
+		VERBOSE_TOROUT_STRING("rcu_torture_boost finished holdoff period");
+	}
 
 	/* Set real-time priority. */
 	sched_set_fifo_low(current);
@@ -1236,6 +1248,7 @@ checkwait:	if (stutter_wait("rcu_torture_boost"))
 			sched_set_fifo_low(current);
 	} while (!torture_must_stop());
 
+cleanup:
 	/* Clean up and exit. */
 	while (!kthread_should_stop()) {
 		torture_shutdown_absorb("rcu_torture_boost");
@@ -2523,7 +2536,7 @@ rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, const char *tag)
 		 "shuffle_interval=%d stutter=%d irqreader=%d "
 		 "fqs_duration=%d fqs_holdoff=%d fqs_stutter=%d "
 		 "test_boost=%d/%d test_boost_interval=%d "
-		 "test_boost_duration=%d shutdown_secs=%d "
+		 "test_boost_duration=%d test_boost_holdoff=%d shutdown_secs=%d "
 		 "stall_cpu=%d stall_cpu_holdoff=%d stall_cpu_irqsoff=%d "
 		 "stall_cpu_block=%d stall_cpu_repeat=%d "
 		 "n_barrier_cbs=%d "
@@ -2537,7 +2550,7 @@ rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, const char *tag)
 		 stat_interval, verbose, test_no_idle_hz, shuffle_interval,
 		 stutter, irqreader, fqs_duration, fqs_holdoff, fqs_stutter,
 		 test_boost, cur_ops->can_boost,
-		 test_boost_interval, test_boost_duration, shutdown_secs,
+		 test_boost_interval, test_boost_duration, test_boost_holdoff, shutdown_secs,
 		 stall_cpu, stall_cpu_holdoff, stall_cpu_irqsoff,
 		 stall_cpu_block, stall_cpu_repeat,
 		 n_barrier_cbs,
-- 
2.40.1

[PATCH rcu v2] 03/11] rcutorture: Include grace-period sequence numbers in failure/close-call

[Paul E. McKenney]

This commit includes the grace-period sequence numbers at the beginning
and end of each segment in the "Failure/close-call rcutorture reader
segments" list.  These are in hexadecimal, and only the bottom byte.
Currently, only RCU is supported, with its three sequence numbers (normal,
expedited, and polled).

Note that if all the grace-period sequence numbers remain the same across
a given reader segment, only one copy of the number will be printed.
Of course, if there is a change, both sets of values will be printed.

Because the overhead of collecting this information can suppress
heisenbugs, this information is collected and printed only in kernels
built with CONFIG_RCU_TORTURE_TEST_LOG_GP=y.

[ paulmck: Apply Nathan Chancellor feedback for IS_ENABLED(). ]
[ paulmck: Apply feedback from kernel test robot. ]

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: kernel test robot <oliver.sang@intel.com>
---
 kernel/rcu/Kconfig.debug | 14 ++++++++++++++
 kernel/rcu/rcu.h         |  2 ++
 kernel/rcu/rcutorture.c  | 34 ++++++++++++++++++++++++++++++++++
 kernel/rcu/tiny.c        | 14 ++++++++++++++
 kernel/rcu/tree.c        | 20 ++++++++++++++++++++
 5 files changed, 84 insertions(+)

diff --git a/kernel/rcu/Kconfig.debug b/kernel/rcu/Kconfig.debug
index 6af90510a1ca..25a9dc2be0dc 100644
--- a/kernel/rcu/Kconfig.debug
+++ b/kernel/rcu/Kconfig.debug
@@ -84,6 +84,20 @@ config RCU_TORTURE_TEST_LOG_CPU
 	  Say Y here if you want CPU IDs logged.
 	  Say N if you are unsure.
 
+config RCU_TORTURE_TEST_LOG_GP
+	bool "Log grace-period numbers for rcutorture failures"
+	depends on RCU_TORTURE_TEST
+	default n
+	help
+	  This option causes rcutorture to decorate each entry of its
+	  log of failure/close-call rcutorture reader segments with the
+	  corresponding grace-period sequence numbers.	This information
+	  can be useful, but it does incur additional overhead, overhead
+	  that can make both failures and close calls less probable.
+
+	  Say Y here if you want grace-period sequence numbers logged.
+	  Say N if you are unsure.
+
 config RCU_REF_SCALE_TEST
 	tristate "Scalability tests for read-side synchronization (RCU and others)"
 	depends on DEBUG_KERNEL
diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index f6fcf87d9139..7c14eec7c13a 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -590,6 +590,8 @@ void do_trace_rcu_torture_read(const char *rcutorturename,
 #endif
 static inline void rcu_gp_set_torture_wait(int duration) { }
 #endif
+unsigned long rcutorture_gather_gp_seqs(void);
+void rcutorture_format_gp_seqs(unsigned long seqs, char *cp);
 
 #ifdef CONFIG_TINY_SRCU
 
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 978893398465..7af7de168846 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -273,6 +273,8 @@ struct rt_read_seg {
 	bool rt_preempted;
 	int rt_cpu;
 	int rt_end_cpu;
+	unsigned long rt_gp_seq;
+	unsigned long rt_gp_seq_end;
 };
 static int err_segs_recorded;
 static struct rt_read_seg err_segs[RCUTORTURE_RDR_MAX_SEGS];
@@ -407,6 +409,8 @@ struct rcu_torture_ops {
 	void (*gp_slow_register)(atomic_t *rgssp);
 	void (*gp_slow_unregister)(atomic_t *rgssp);
 	bool (*reader_blocked)(void);
+	unsigned long (*gather_gp_seqs)(void);
+	void (*format_gp_seqs)(unsigned long seqs, char *cp);
 	long cbflood_max;
 	int irq_capable;
 	int can_boost;
@@ -611,6 +615,8 @@ static struct rcu_torture_ops rcu_ops = {
 	.reader_blocked		= IS_ENABLED(CONFIG_RCU_TORTURE_TEST_LOG_CPU)
 				  ? has_rcu_reader_blocked
 				  : NULL,
+	.gather_gp_seqs		= rcutorture_gather_gp_seqs,
+	.format_gp_seqs		= rcutorture_format_gp_seqs,
 	.irq_capable		= 1,
 	.can_boost		= IS_ENABLED(CONFIG_RCU_BOOST),
 	.extendables		= RCUTORTURE_MAX_EXTEND,
@@ -656,6 +662,8 @@ static struct rcu_torture_ops rcu_busted_ops = {
 	.sync		= synchronize_rcu_busted,
 	.exp_sync	= synchronize_rcu_busted,
 	.call		= call_rcu_busted,
+	.gather_gp_seqs	= rcutorture_gather_gp_seqs,
+	.format_gp_seqs	= rcutorture_format_gp_seqs,
 	.irq_capable	= 1,
 	.extendables	= RCUTORTURE_MAX_EXTEND,
 	.name		= "busted"
@@ -1989,6 +1997,12 @@ static void rcutorture_one_extend(int *readstate, int newstate, bool insoftirq,
 				rtrsp[-1].rt_preempted = cur_ops->reader_blocked();
 		}
 	}
+	// Sample grace-period sequence number, as good a place as any.
+	if (IS_ENABLED(CONFIG_RCU_TORTURE_TEST_LOG_GP) && cur_ops->gather_gp_seqs) {
+		rtrsp->rt_gp_seq = cur_ops->gather_gp_seqs();
+		if (!first)
+			rtrsp[-1].rt_gp_seq_end = rtrsp->rt_gp_seq;
+	}
 
 	/*
 	 * Next, remove old protection, in decreasing order of strength
@@ -3577,6 +3591,7 @@ rcu_torture_cleanup(void)
 	int flags = 0;
 	unsigned long gp_seq = 0;
 	int i;
+	int j;
 
 	if (torture_cleanup_begin()) {
 		if (cur_ops->cb_barrier != NULL) {
@@ -3672,6 +3687,25 @@ rcu_torture_cleanup(void)
 				else
 					pr_cont(" ...");
 			}
+			if (IS_ENABLED(CONFIG_RCU_TORTURE_TEST_LOG_GP) &&
+			    cur_ops->gather_gp_seqs && cur_ops->format_gp_seqs) {
+				char buf1[16+1];
+				char buf2[16+1];
+				char sepchar = '-';
+
+				cur_ops->format_gp_seqs(err_segs[i].rt_gp_seq, buf1);
+				cur_ops->format_gp_seqs(err_segs[i].rt_gp_seq_end, buf2);
+				if (err_segs[i].rt_gp_seq == err_segs[i].rt_gp_seq_end) {
+					if (buf2[0]) {
+						for (j = 0; buf2[j]; j++)
+							buf2[j] = '.';
+						if (j)
+							buf2[j - 1] = ' ';
+					}
+					sepchar = ' ';
+				}
+				pr_cont(" %s%c%s", buf1, sepchar, buf2);
+			}
 			if (err_segs[i].rt_delay_ms != 0) {
 				pr_cont(" %s%ldms", firsttime ? "" : "+",
 					err_segs[i].rt_delay_ms);
diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
index b3b3ce34df63..773944257e79 100644
--- a/kernel/rcu/tiny.c
+++ b/kernel/rcu/tiny.c
@@ -257,6 +257,20 @@ void kvfree_call_rcu(struct rcu_head *head, void *ptr)
 EXPORT_SYMBOL_GPL(kvfree_call_rcu);
 #endif
 
+#if IS_ENABLED(CONFIG_RCU_TORTURE_TEST)
+unsigned long rcutorture_gather_gp_seqs(void)
+{
+	return READ_ONCE(rcu_ctrlblk.gp_seq) & 0xff;
+}
+EXPORT_SYMBOL_GPL(rcutorture_gather_gp_seqs);
+
+void rcutorture_format_gp_seqs(unsigned long seqs, char *cp)
+{
+	snprintf(cp, 8, "g%02lx", seqs & 0xff);
+}
+EXPORT_SYMBOL_GPL(rcutorture_format_gp_seqs);
+#endif
+
 void __init rcu_init(void)
 {
 	open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 9ba34206e20d..574a28066062 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -559,6 +559,26 @@ void rcutorture_get_gp_data(int *flags, unsigned long *gp_seq)
 }
 EXPORT_SYMBOL_GPL(rcutorture_get_gp_data);
 
+/* Gather grace-period sequence numbers for rcutorture diagnostics. */
+unsigned long rcutorture_gather_gp_seqs(void)
+{
+	return ((READ_ONCE(rcu_state.gp_seq) & 0xff) << 16) |
+	       ((READ_ONCE(rcu_state.expedited_sequence) & 0xff) << 8) |
+	       (READ_ONCE(rcu_state.gp_seq_polled) & 0xff);
+}
+EXPORT_SYMBOL_GPL(rcutorture_gather_gp_seqs);
+
+/* Format grace-period sequence numbers for rcutorture diagnostics. */
+void rcutorture_format_gp_seqs(unsigned long seqs, char *cp)
+{
+	unsigned int egp = (seqs >> 8) & 0xff;
+	unsigned int ggp = (seqs >> 16) & 0xff;
+	unsigned int pgp = seqs & 0xff;
+
+	snprintf(cp, 16, "g%02x:e%02x:p%02x", ggp, egp, pgp);
+}
+EXPORT_SYMBOL_GPL(rcutorture_format_gp_seqs);
+
 #if defined(CONFIG_NO_HZ_FULL) && (!defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_KVM_XFER_TO_GUEST_WORK))
 /*
  * An empty function that will trigger a reschedule on
-- 
2.40.1

[PATCH rcu v2] 04/11] rcutorture: Expand failure/close-call grace-period output

[Paul E. McKenney]

With only eight bits per grace-period sequence number, wrap can happen
in 64 grace periods.  This commit therefore increases this to sixteen
bits for normal grace-period sequence numbers and the combined short-form
polling sequence numbers, thus deferring wrap for at least 16,384 grace
periods.  Because expedited grace periods go faster, expand these to 24
bits, deferring wrap for at least 4,194,304 expedited grace periods.
These longer wrap times makes it easier to correlate these numbers to
trace-event output.

Note that the low-order two bits are reserved for intra-grace-period
state, hence the above wrap numbers being a factor of four smaller than
you might expect.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/rcu.h        |  4 ++--
 kernel/rcu/rcutorture.c | 12 ++++++------
 kernel/rcu/tiny.c       |  8 ++++----
 kernel/rcu/tree.c       | 18 +++++++++---------
 4 files changed, 21 insertions(+), 21 deletions(-)

diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index 7c14eec7c13a..d2a91f705a4a 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -590,8 +590,8 @@ void do_trace_rcu_torture_read(const char *rcutorturename,
 #endif
 static inline void rcu_gp_set_torture_wait(int duration) { }
 #endif
-unsigned long rcutorture_gather_gp_seqs(void);
-void rcutorture_format_gp_seqs(unsigned long seqs, char *cp);
+unsigned long long rcutorture_gather_gp_seqs(void);
+void rcutorture_format_gp_seqs(unsigned long long seqs, char *cp);
 
 #ifdef CONFIG_TINY_SRCU
 
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 7af7de168846..5b0510c79fde 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -273,8 +273,8 @@ struct rt_read_seg {
 	bool rt_preempted;
 	int rt_cpu;
 	int rt_end_cpu;
-	unsigned long rt_gp_seq;
-	unsigned long rt_gp_seq_end;
+	unsigned long long rt_gp_seq;
+	unsigned long long rt_gp_seq_end;
 };
 static int err_segs_recorded;
 static struct rt_read_seg err_segs[RCUTORTURE_RDR_MAX_SEGS];
@@ -409,8 +409,8 @@ struct rcu_torture_ops {
 	void (*gp_slow_register)(atomic_t *rgssp);
 	void (*gp_slow_unregister)(atomic_t *rgssp);
 	bool (*reader_blocked)(void);
-	unsigned long (*gather_gp_seqs)(void);
-	void (*format_gp_seqs)(unsigned long seqs, char *cp);
+	unsigned long long (*gather_gp_seqs)(void);
+	void (*format_gp_seqs)(unsigned long long seqs, char *cp);
 	long cbflood_max;
 	int irq_capable;
 	int can_boost;
@@ -3689,8 +3689,8 @@ rcu_torture_cleanup(void)
 			}
 			if (IS_ENABLED(CONFIG_RCU_TORTURE_TEST_LOG_GP) &&
 			    cur_ops->gather_gp_seqs && cur_ops->format_gp_seqs) {
-				char buf1[16+1];
-				char buf2[16+1];
+				char buf1[20+1];
+				char buf2[20+1];
 				char sepchar = '-';
 
 				cur_ops->format_gp_seqs(err_segs[i].rt_gp_seq, buf1);
diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
index 773944257e79..b97c64e99a90 100644
--- a/kernel/rcu/tiny.c
+++ b/kernel/rcu/tiny.c
@@ -258,15 +258,15 @@ EXPORT_SYMBOL_GPL(kvfree_call_rcu);
 #endif
 
 #if IS_ENABLED(CONFIG_RCU_TORTURE_TEST)
-unsigned long rcutorture_gather_gp_seqs(void)
+unsigned long long rcutorture_gather_gp_seqs(void)
 {
-	return READ_ONCE(rcu_ctrlblk.gp_seq) & 0xff;
+	return READ_ONCE(rcu_ctrlblk.gp_seq) & 0xffffULL;
 }
 EXPORT_SYMBOL_GPL(rcutorture_gather_gp_seqs);
 
-void rcutorture_format_gp_seqs(unsigned long seqs, char *cp)
+void rcutorture_format_gp_seqs(unsigned long long seqs, char *cp)
 {
-	snprintf(cp, 8, "g%02lx", seqs & 0xff);
+	snprintf(cp, 8, "g%04llx", seqs & 0xffffULL);
 }
 EXPORT_SYMBOL_GPL(rcutorture_format_gp_seqs);
 #endif
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 574a28066062..ac596596e771 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -560,22 +560,22 @@ void rcutorture_get_gp_data(int *flags, unsigned long *gp_seq)
 EXPORT_SYMBOL_GPL(rcutorture_get_gp_data);
 
 /* Gather grace-period sequence numbers for rcutorture diagnostics. */
-unsigned long rcutorture_gather_gp_seqs(void)
+unsigned long long rcutorture_gather_gp_seqs(void)
 {
-	return ((READ_ONCE(rcu_state.gp_seq) & 0xff) << 16) |
-	       ((READ_ONCE(rcu_state.expedited_sequence) & 0xff) << 8) |
-	       (READ_ONCE(rcu_state.gp_seq_polled) & 0xff);
+	return ((READ_ONCE(rcu_state.gp_seq) & 0xffffULL) << 40) |
+	       ((READ_ONCE(rcu_state.expedited_sequence) & 0xffffffULL) << 16) |
+	       (READ_ONCE(rcu_state.gp_seq_polled) & 0xffffULL);
 }
 EXPORT_SYMBOL_GPL(rcutorture_gather_gp_seqs);
 
 /* Format grace-period sequence numbers for rcutorture diagnostics. */
-void rcutorture_format_gp_seqs(unsigned long seqs, char *cp)
+void rcutorture_format_gp_seqs(unsigned long long seqs, char *cp)
 {
-	unsigned int egp = (seqs >> 8) & 0xff;
-	unsigned int ggp = (seqs >> 16) & 0xff;
-	unsigned int pgp = seqs & 0xff;
+	unsigned int egp = (seqs >> 16) & 0xffffffULL;
+	unsigned int ggp = (seqs >> 40) & 0xffffULL;
+	unsigned int pgp = seqs & 0xffffULL;
 
-	snprintf(cp, 16, "g%02x:e%02x:p%02x", ggp, egp, pgp);
+	snprintf(cp, 20, "g%04x:e%06x:p%04x", ggp, egp, pgp);
 }
 EXPORT_SYMBOL_GPL(rcutorture_format_gp_seqs);
 
-- 
2.40.1

[PATCH rcu v2] 05/11] rcu: Trace expedited grace-period numbers in hexadecimal

[Paul E. McKenney]

This commit reformats the expedited grace-period numbers into hexadecimal
for easier decoding and comparison.  The normal grace-period numbers
remain in decimal for the time being.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 include/trace/events/rcu.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
index e81431deaa50..63fd8aa99af7 100644
--- a/include/trace/events/rcu.h
+++ b/include/trace/events/rcu.h
@@ -207,7 +207,7 @@ TRACE_EVENT_RCU(rcu_exp_grace_period,
 		__entry->gpevent = gpevent;
 	),
 
-	TP_printk("%s %ld %s",
+	TP_printk("%s %#lx %s",
 		  __entry->rcuname, __entry->gpseq, __entry->gpevent)
 );
 
-- 
2.40.1

[PATCH rcu v2] 06/11] rcutorture: Add ftrace-compatible timestamp to GP# failure/close-call output

[Paul E. McKenney]

This commit adds an ftrace-compatible microsecond-scale timestamp
to the failure/close-call output, but only in kernels built with
CONFIG_RCU_TORTURE_TEST_LOG_GP=y.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/rcutorture.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 5b0510c79fde..0f5a94542719 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -275,6 +275,7 @@ struct rt_read_seg {
 	int rt_end_cpu;
 	unsigned long long rt_gp_seq;
 	unsigned long long rt_gp_seq_end;
+	u64 rt_ts;
 };
 static int err_segs_recorded;
 static struct rt_read_seg err_segs[RCUTORTURE_RDR_MAX_SEGS];
@@ -2000,6 +2001,7 @@ static void rcutorture_one_extend(int *readstate, int newstate, bool insoftirq,
 	// Sample grace-period sequence number, as good a place as any.
 	if (IS_ENABLED(CONFIG_RCU_TORTURE_TEST_LOG_GP) && cur_ops->gather_gp_seqs) {
 		rtrsp->rt_gp_seq = cur_ops->gather_gp_seqs();
+		rtrsp->rt_ts = ktime_get_mono_fast_ns();
 		if (!first)
 			rtrsp[-1].rt_gp_seq_end = rtrsp->rt_gp_seq;
 	}
@@ -3674,7 +3676,11 @@ rcu_torture_cleanup(void)
 			pr_alert("\t: No segments recorded!!!\n");
 		firsttime = 1;
 		for (i = 0; i < rt_read_nsegs; i++) {
-			pr_alert("\t%d: %#4x", i, err_segs[i].rt_readstate);
+			if (IS_ENABLED(CONFIG_RCU_TORTURE_TEST_LOG_GP))
+				pr_alert("\t%lluus ", div64_u64(err_segs[i].rt_ts, 1000ULL));
+			else
+				pr_alert("\t");
+			pr_cont("%d: %#4x", i, err_segs[i].rt_readstate);
 			if (err_segs[i].rt_delay_jiffies != 0) {
 				pr_cont("%s%ldjiffies", firsttime ? "" : "+",
 					err_segs[i].rt_delay_jiffies);
-- 
2.40.1

[PATCH rcu v2] 07/11] rcutorture: Make cur_ops->format_gp_seqs take buffer length

[Paul E. McKenney]

The Tree and Tiny implementations of rcutorture_format_gp_seqs() use
hard-coded constants for the length of the buffer that they format into.
This is of course an accident waiting to happen, so this commit therefore
makes them take a length argument.  The rcutorture calling code uses
ARRAY_SIZE() to safely compute this new argument.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/rcu.h        | 2 +-
 kernel/rcu/rcutorture.c | 8 +++++---
 kernel/rcu/tiny.c       | 4 ++--
 kernel/rcu/tree.c       | 4 ++--
 4 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index d2a91f705a4a..eed2951a4962 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -591,7 +591,7 @@ void do_trace_rcu_torture_read(const char *rcutorturename,
 static inline void rcu_gp_set_torture_wait(int duration) { }
 #endif
 unsigned long long rcutorture_gather_gp_seqs(void);
-void rcutorture_format_gp_seqs(unsigned long long seqs, char *cp);
+void rcutorture_format_gp_seqs(unsigned long long seqs, char *cp, size_t len);
 
 #ifdef CONFIG_TINY_SRCU
 
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 0f5a94542719..2e6e8664e403 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -411,7 +411,7 @@ struct rcu_torture_ops {
 	void (*gp_slow_unregister)(atomic_t *rgssp);
 	bool (*reader_blocked)(void);
 	unsigned long long (*gather_gp_seqs)(void);
-	void (*format_gp_seqs)(unsigned long long seqs, char *cp);
+	void (*format_gp_seqs)(unsigned long long seqs, char *cp, size_t len);
 	long cbflood_max;
 	int irq_capable;
 	int can_boost;
@@ -3699,8 +3699,10 @@ rcu_torture_cleanup(void)
 				char buf2[20+1];
 				char sepchar = '-';
 
-				cur_ops->format_gp_seqs(err_segs[i].rt_gp_seq, buf1);
-				cur_ops->format_gp_seqs(err_segs[i].rt_gp_seq_end, buf2);
+				cur_ops->format_gp_seqs(err_segs[i].rt_gp_seq,
+							buf1, ARRAY_SIZE(buf1));
+				cur_ops->format_gp_seqs(err_segs[i].rt_gp_seq_end,
+							buf2, ARRAY_SIZE(buf2));
 				if (err_segs[i].rt_gp_seq == err_segs[i].rt_gp_seq_end) {
 					if (buf2[0]) {
 						for (j = 0; buf2[j]; j++)
diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
index b97c64e99a90..6380fbd27557 100644
--- a/kernel/rcu/tiny.c
+++ b/kernel/rcu/tiny.c
@@ -264,9 +264,9 @@ unsigned long long rcutorture_gather_gp_seqs(void)
 }
 EXPORT_SYMBOL_GPL(rcutorture_gather_gp_seqs);
 
-void rcutorture_format_gp_seqs(unsigned long long seqs, char *cp)
+void rcutorture_format_gp_seqs(unsigned long long seqs, char *cp, size_t len)
 {
-	snprintf(cp, 8, "g%04llx", seqs & 0xffffULL);
+	snprintf(cp, len, "g%04llx", seqs & 0xffffULL);
 }
 EXPORT_SYMBOL_GPL(rcutorture_format_gp_seqs);
 #endif
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index ac596596e771..1d201455aa7c 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -569,13 +569,13 @@ unsigned long long rcutorture_gather_gp_seqs(void)
 EXPORT_SYMBOL_GPL(rcutorture_gather_gp_seqs);
 
 /* Format grace-period sequence numbers for rcutorture diagnostics. */
-void rcutorture_format_gp_seqs(unsigned long long seqs, char *cp)
+void rcutorture_format_gp_seqs(unsigned long long seqs, char *cp, size_t len)
 {
 	unsigned int egp = (seqs >> 16) & 0xffffffULL;
 	unsigned int ggp = (seqs >> 40) & 0xffffULL;
 	unsigned int pgp = seqs & 0xffffULL;
 
-	snprintf(cp, 20, "g%04x:e%06x:p%04x", ggp, egp, pgp);
+	snprintf(cp, len, "g%04x:e%06x:p%04x", ggp, egp, pgp);
 }
 EXPORT_SYMBOL_GPL(rcutorture_format_gp_seqs);
 
-- 
2.40.1

[PATCH rcu v2] 08/11] rcutorture: Move RCU_TORTURE_TEST_{CHK_RDR_STATE,LOG_CPU} to bool

[Paul E. McKenney]

The RCU_TORTURE_TEST_CHK_RDR_STATE and RCU_TORTURE_TEST_LOG_CPU Kconfig
options are pointlessly defined as tristate.  This commit therefore
converts them to bool.

Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202412241458.150d082b-lkp@intel.com
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/Kconfig.debug | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/rcu/Kconfig.debug b/kernel/rcu/Kconfig.debug
index 25a9dc2be0dc..12e4c64ebae1 100644
--- a/kernel/rcu/Kconfig.debug
+++ b/kernel/rcu/Kconfig.debug
@@ -54,7 +54,7 @@ config RCU_TORTURE_TEST
 	  Say N if you are unsure.
 
 config RCU_TORTURE_TEST_CHK_RDR_STATE
-	tristate "Check rcutorture reader state"
+	bool "Check rcutorture reader state"
 	depends on RCU_TORTURE_TEST
 	default n
 	help
@@ -70,7 +70,7 @@ config RCU_TORTURE_TEST_CHK_RDR_STATE
 	  Say N if you are unsure.
 
 config RCU_TORTURE_TEST_LOG_CPU
-	tristate "Log CPU for rcutorture failures"
+	bool "Log CPU for rcutorture failures"
 	depends on RCU_TORTURE_TEST
 	default n
 	help
-- 
2.40.1

[PATCH rcu v2] 09/11] rcutorture: Complain when invalid SRCU reader_flavor is specified

[Paul E. McKenney]

Currently, rcutorture ignores reader_flavor bits that are not in the
SRCU_READ_FLAVOR_ALL bitmask, which could confuse rcutorture users into
believing buggy patches had been fully tested.  This commit therefore
produces a splat in this case.

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

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 2e6e8664e403..36bc8d1332d4 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -690,6 +690,8 @@ static int srcu_torture_read_lock(void)
 	struct srcu_ctr __percpu *scp;
 	int ret = 0;
 
+	WARN_ON_ONCE(reader_flavor & ~SRCU_READ_FLAVOR_ALL);
+
 	if ((reader_flavor & SRCU_READ_FLAVOR_NORMAL) || !(reader_flavor & SRCU_READ_FLAVOR_ALL)) {
 		idx = srcu_read_lock(srcu_ctlp);
 		WARN_ON_ONCE(idx & ~0x1);
-- 
2.40.1

[PATCH rcu v2] 10/11] srcu: Add FORCE_NEED_SRCU_NMI_SAFE Kconfig for testing

[Paul E. McKenney]

The srcu_read_lock_nmisafe() and srcu_read_unlock_nmisafe() functions
map to __srcu_read_lock() and __srcu_read_unlock() on systems like x86
that have NMI-safe this_cpu_inc() operations.  This makes the underlying
__srcu_read_lock_nmisafe() and __srcu_read_unlock_nmisafe() functions
difficult to test on (for example) x86 systems, allowing bugs to creep in.

This commit therefore creates a FORCE_NEED_SRCU_NMI_SAFE Kconfig that
forces those underlying functions to be used even on systems where they
are not needed, thus providing better testing coverage.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/Kconfig | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig
index 80242957fa41..aa42de4d2768 100644
--- a/kernel/rcu/Kconfig
+++ b/kernel/rcu/Kconfig
@@ -65,6 +65,17 @@ config TREE_SRCU
 	help
 	  This option selects the full-fledged version of SRCU.
 
+config FORCE_NEED_SRCU_NMI_SAFE
+	bool "Force selection of NEED_SRCU_NMI_SAFE"
+	depends on !TINY_SRCU
+	select NEED_SRCU_NMI_SAFE
+	default n
+	help
+	  This option forces selection of the NEED_SRCU_NMI_SAFE
+	  Kconfig option, allowing testing of srcu_read_lock_nmisafe()
+	  and srcu_read_unlock_nmisafe() on architectures (like x86)
+	  that select the ARCH_HAS_NMI_SAFE_THIS_CPU_OPS Kconfig option.
+
 config NEED_SRCU_NMI_SAFE
 	def_bool HAVE_NMI && !ARCH_HAS_NMI_SAFE_THIS_CPU_OPS && !TINY_SRCU
 
-- 
2.40.1

[PATCH rcu v2] 11/11] torture: Make SRCU lockdep testing use srcu_read_lock_nmisafe()

[Paul E. McKenney]

Recent experience shows that the srcu_read_lock_nmisafe() and
srcu_read_unlock_nmisafe() functions are not sufficiently tested.
This commit therefore causes the torture.sh script's SRCU lockdep testing
to use these two functions.  This will cause these two functions to
be regularly tested by several developers (myself included) who use
torture.sh as an RCU acceptance test.

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

diff --git a/tools/testing/selftests/rcutorture/bin/srcu_lockdep.sh b/tools/testing/selftests/rcutorture/bin/srcu_lockdep.sh
index 2e63ef009d59..2db12c5cad9c 100755
--- a/tools/testing/selftests/rcutorture/bin/srcu_lockdep.sh
+++ b/tools/testing/selftests/rcutorture/bin/srcu_lockdep.sh
@@ -49,7 +49,7 @@ do
 		do
 			err=
 			val=$((d*1000+t*10+c))
-			tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration 5s --configs "SRCU-P" --bootargs "rcutorture.test_srcu_lockdep=$val" --trust-make --datestamp "$ds/$val" > "$T/kvm.sh.out" 2>&1
+			tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration 5s --configs "SRCU-P" --kconfig "CONFIG_FORCE_NEED_SRCU_NMI_SAFE=y" --bootargs "rcutorture.test_srcu_lockdep=$val rcutorture.reader_flavor=0x2" --trust-make --datestamp "$ds/$val" > "$T/kvm.sh.out" 2>&1
 			ret=$?
 			mv "$T/kvm.sh.out" "$RCUTORTURE/res/$ds/$val"
 			if test "$d" -ne 0 && test "$ret" -eq 0
-- 
2.40.1