[PATCH rcu 01/12] torture: Make kvm-remote.sh announce which system is being waited on

[PATCH rcu 01/12] torture: Make kvm-remote.sh announce which system is being waited on

[Paul E. McKenney]

If a remote system fails in certain ways, for example, if it is rebooted
without removing the contents of the /tmp directory, its remote.run file
never will be removed and the kvm-remote.sh script will loop waiting
forever.  The manual workaround for this (hopefully!) rare event is to
manually remove the file, which will cause the results up to the reboot
to be collected and evaluated.

Unfortunately, to work out which system is holding things up, the user
must refer to the name of the last system whose results were collected,
then look up the name of the next system in sequence, then manually
remove the remote.run file.  Even more unfortunately, this procedure can
be fooled in runs where each system handles more than one batch should
a given system take longer than expected, causing the systems to be
handled out of order.

This commit therefore causes kvm-remote.sh to print out the name of
the system it will wait on next, allowing the user to refer directly
to that name.  Making the kvm-remote.sh script automatically handle
unscheduled termination of the qemu processes is left as future work.
Quite possibly deep future work.

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

diff --git a/tools/testing/selftests/rcutorture/bin/kvm-remote.sh b/tools/testing/selftests/rcutorture/bin/kvm-remote.sh
index 0ff59bd8b640d..9f0a5d5ff2ddc 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm-remote.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm-remote.sh
@@ -262,6 +262,7 @@ echo All batches started. `date` | tee -a "$oldrun/remote-log"
 # Wait for all remaining scenarios to complete and collect results.
 for i in $systems
 do
+	echo " ---" Waiting for $i `date` | tee -a "$oldrun/remote-log"
 	while checkremotefile "$i" "$resdir/$ds/remote.run"
 	do
 		sleep 30
-- 
2.31.1.189.g2e36527f23

[PATCH rcu 02/12] rcu/torture: Change order of warning and trace dump

[Paul E. McKenney]

From: Anna-Maria Behnsen <anna-maria@linutronix.de>

Dumping a big ftrace buffer could lead to a RCU stall. So there is the
ftrace buffer and the stall information which needs to be printed. When
there is additionaly a WARN_ON() which describes the reason for the ftrace
buffer dump and the WARN_ON() is executed _after_ ftrace buffer dump, the
information get lost in the middle of the RCU stall information.

Therefore print WARN_ON() message before dumping the ftrace buffer in
rcu_torture_writer().

[ paulmck: Add tracing_off() to avoid cruft from WARN(). ]

Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Reviewed-by: Benedikt Spranger <b.spranger@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/rcutorture.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 7120165a93426..3032dd7c7ad35 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1321,8 +1321,9 @@ rcu_torture_writer(void *arg)
 				if (list_empty(&rcu_tortures[i].rtort_free) &&
 				    rcu_access_pointer(rcu_torture_current) !=
 				    &rcu_tortures[i]) {
-					rcu_ftrace_dump(DUMP_ALL);
+					tracing_off();
 					WARN(1, "%s: rtort_pipe_count: %d\n", __func__, rcu_tortures[i].rtort_pipe_count);
+					rcu_ftrace_dump(DUMP_ALL);
 				}
 		if (stutter_waited)
 			sched_set_normal(current, oldnice);
-- 
2.31.1.189.g2e36527f23

[PATCH rcu 03/12] rcutorture: Simplify rcu_torture_read_exit_child() loop

[Paul E. McKenney]

The existing loop has an implicit manual loop that obscures the flow
and requires an extra control variable.  This commit makes this implicit
loop explicit, thus saving several lines of code.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/rcutorture.c | 47 ++++++++++++++++++-----------------------
 1 file changed, 20 insertions(+), 27 deletions(-)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 3032dd7c7ad35..9273264772b88 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -2874,7 +2874,6 @@ static int rcu_torture_read_exit_child(void *trsp_in)
 // Parent kthread which creates and destroys read-exit child kthreads.
 static int rcu_torture_read_exit(void *unused)
 {
-	int count = 0;
 	bool errexit = false;
 	int i;
 	struct task_struct *tsp;
@@ -2886,34 +2885,28 @@ static int rcu_torture_read_exit(void *unused)
 
 	// Each pass through this loop does one read-exit episode.
 	do {
-		if (++count > read_exit_burst) {
-			VERBOSE_TOROUT_STRING("rcu_torture_read_exit: End of episode");
-			rcu_barrier(); // Wait for task_struct free, avoid OOM.
-			for (i = 0; i < read_exit_delay; i++) {
-				schedule_timeout_uninterruptible(HZ);
-				if (READ_ONCE(read_exit_child_stop))
-					break;
+		VERBOSE_TOROUT_STRING("rcu_torture_read_exit: Start of episode");
+		for (i = 0; i < read_exit_burst; i++) {
+			if (READ_ONCE(read_exit_child_stop))
+				break;
+			stutter_wait("rcu_torture_read_exit");
+			// Spawn child.
+			tsp = kthread_run(rcu_torture_read_exit_child,
+					  &trs, "%s", "rcu_torture_read_exit_child");
+			if (IS_ERR(tsp)) {
+				TOROUT_ERRSTRING("out of memory");
+				errexit = true;
+				break;
 			}
-			if (!READ_ONCE(read_exit_child_stop))
-				VERBOSE_TOROUT_STRING("rcu_torture_read_exit: Start of episode");
-			count = 0;
-		}
-		if (READ_ONCE(read_exit_child_stop))
-			break;
-		// Spawn child.
-		tsp = kthread_run(rcu_torture_read_exit_child,
-				     &trs, "%s",
-				     "rcu_torture_read_exit_child");
-		if (IS_ERR(tsp)) {
-			TOROUT_ERRSTRING("out of memory");
-			errexit = true;
-			tsp = NULL;
-			break;
+			cond_resched();
+			kthread_stop(tsp);
+			n_read_exits ++;
 		}
-		cond_resched();
-		kthread_stop(tsp);
-		n_read_exits ++;
-		stutter_wait("rcu_torture_read_exit");
+		VERBOSE_TOROUT_STRING("rcu_torture_read_exit: End of episode");
+		rcu_barrier(); // Wait for task_struct free, avoid OOM.
+		i = 0;
+		for (; !errexit && !READ_ONCE(read_exit_child_stop) && i < read_exit_delay; i++)
+			schedule_timeout_uninterruptible(HZ);
 	} while (!errexit && !READ_ONCE(read_exit_child_stop));
 
 	// Clean up and exit.
-- 
2.31.1.189.g2e36527f23

[PATCH rcu 04/12] rcutorture: Fix memory leak in rcu_test_debug_objects()

[Paul E. McKenney]

From: Zqiang <qiang1.zhang@intel.com>

The kernel memory leak detector located the following:

unreferenced object 0xffff95d941135b50 (size 16):
  comm "swapper/0", pid 1, jiffies 4294667610 (age 1367.451s)
  hex dump (first 16 bytes):
    f0 c6 c2 bd d9 95 ff ff 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<00000000bc81d9b1>] kmem_cache_alloc_trace+0x2f6/0x500
    [<00000000d28be229>] rcu_torture_init+0x1235/0x1354
    [<0000000032c3acd9>] do_one_initcall+0x51/0x210
    [<000000003c117727>] kernel_init_freeable+0x205/0x259
    [<000000003961f965>] kernel_init+0x1a/0x120
    [<000000001998f890>] ret_from_fork+0x22/0x30

This is caused by the rcu_test_debug_objects() function allocating an
rcu_head structure, then failing to free it.  This commit therefore adds
the needed kfree() after the last use of this structure.

Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/rcutorture.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 9273264772b88..613711b8242b9 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -3116,6 +3116,7 @@ static void rcu_test_debug_objects(void)
 	pr_alert("%s: WARN: Duplicate call_rcu() test complete.\n", KBUILD_MODNAME);
 	destroy_rcu_head_on_stack(&rh1);
 	destroy_rcu_head_on_stack(&rh2);
+	kfree(rhp);
 #else /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
 	pr_alert("%s: !CONFIG_DEBUG_OBJECTS_RCU_HEAD, not testing duplicate call_rcu()\n", KBUILD_MODNAME);
 #endif /* #else #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
-- 
2.31.1.189.g2e36527f23

[PATCH rcu 05/12] torture: Adjust to again produce debugging information

[Paul E. McKenney]

A recent change to the DEBUG_INFO Kconfig option means that simply adding
CONFIG_DEBUG_INFO=y to the .config file and running "make oldconfig" no
longer works.  It is instead necessary to add CONFIG_DEBUG_INFO_NONE=n
and (for example) CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y.
This combination will then result in CONFIG_DEBUG_INFO being selected.

This commit therefore updates the Kconfig options produced in response
to the kvm.sh --gdb, --kasan, and --kcsan Kconfig options.

Fixes: f9b3cd245784 ("Kconfig.debug: make DEBUG_INFO selectable from a choice")
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 tools/testing/selftests/rcutorture/bin/kvm.sh | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/rcutorture/bin/kvm.sh b/tools/testing/selftests/rcutorture/bin/kvm.sh
index 263e16aeca0e4..6c734818a8757 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm.sh
@@ -164,7 +164,7 @@ do
 		shift
 		;;
 	--gdb)
-		TORTURE_KCONFIG_GDB_ARG="CONFIG_DEBUG_INFO=y"; export TORTURE_KCONFIG_GDB_ARG
+		TORTURE_KCONFIG_GDB_ARG="CONFIG_DEBUG_INFO_NONE=n CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y"; export TORTURE_KCONFIG_GDB_ARG
 		TORTURE_BOOT_GDB_ARG="nokaslr"; export TORTURE_BOOT_GDB_ARG
 		TORTURE_QEMU_GDB_ARG="-s -S"; export TORTURE_QEMU_GDB_ARG
 		;;
@@ -180,7 +180,7 @@ do
 		shift
 		;;
 	--kasan)
-		TORTURE_KCONFIG_KASAN_ARG="CONFIG_DEBUG_INFO=y CONFIG_KASAN=y"; export TORTURE_KCONFIG_KASAN_ARG
+		TORTURE_KCONFIG_KASAN_ARG="CONFIG_DEBUG_INFO_NONE=n CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y CONFIG_KASAN=y"; export TORTURE_KCONFIG_KASAN_ARG
 		if test -n "$torture_qemu_mem_default"
 		then
 			TORTURE_QEMU_MEM=2G
@@ -192,7 +192,7 @@ do
 		shift
 		;;
 	--kcsan)
-		TORTURE_KCONFIG_KCSAN_ARG="CONFIG_DEBUG_INFO=y CONFIG_KCSAN=y CONFIG_KCSAN_STRICT=y CONFIG_KCSAN_REPORT_ONCE_IN_MS=100000 CONFIG_KCSAN_VERBOSE=y CONFIG_DEBUG_LOCK_ALLOC=y CONFIG_PROVE_LOCKING=y"; export TORTURE_KCONFIG_KCSAN_ARG
+		TORTURE_KCONFIG_KCSAN_ARG="CONFIG_DEBUG_INFO_NONE=n CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y CONFIG_KCSAN=y CONFIG_KCSAN_STRICT=y CONFIG_KCSAN_REPORT_ONCE_IN_MS=100000 CONFIG_KCSAN_VERBOSE=y CONFIG_DEBUG_LOCK_ALLOC=y CONFIG_PROVE_LOCKING=y"; export TORTURE_KCONFIG_KCSAN_ARG
 		;;
 	--kmake-arg|--kmake-args)
 		checkarg --kmake-arg "(kernel make arguments)" $# "$2" '.*' '^error$'
-- 
2.31.1.189.g2e36527f23

[PATCH rcu 06/12] rcutorture: Make failure indication note reader-batch overflow

[Paul E. McKenney]

The loop scanning the pipesummary[] array currently skips the last
element, which means that the diagnostics ignore those rarest of
situations, namely where some readers persist across more than ten
grace periods, but all other readers avoid spanning a full grace period.
This commit therefore adjusts the scan to include the last element of
this array.

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

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 613711b8242b9..64ad5305829b6 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1869,7 +1869,7 @@ rcu_torture_stats_print(void)
 			batchsummary[i] += READ_ONCE(per_cpu(rcu_torture_batch, cpu)[i]);
 		}
 	}
-	for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
+	for (i = RCU_TORTURE_PIPE_LEN; i >= 0; i--) {
 		if (pipesummary[i] != 0)
 			break;
 	}
-- 
2.31.1.189.g2e36527f23

[PATCH rcu 07/12] rcu/rcuscale: Fix smp_processor_id()-in-preemptible warnings

[Paul E. McKenney]

From: Zqiang <qiang1.zhang@intel.com>

Systems built with CONFIG_DEBUG_PREEMPT=y can trigger the following
BUG while running the rcuscale performance test:

BUG: using smp_processor_id() in preemptible [00000000] code: rcu_scale_write/69
CPU: 0 PID: 66 Comm: rcu_scale_write Not tainted 5.18.0-rc7-next-20220517-yoctodev-standard+
caller is debug_smp_processor_id+0x17/0x20
Call Trace:
<TASK>
dump_stack_lvl+0x49/0x5e
dump_stack+0x10/0x12
check_preemption_disabled+0xdf/0xf0
debug_smp_processor_id+0x17/0x20
rcu_scale_writer+0x2b5/0x580
kthread+0x177/0x1b0
ret_from_fork+0x22/0x30
</TASK>

Reproduction method:
runqemu kvm slirp nographic qemuparams="-m 4096 -smp 8" bootparams="isolcpus=2,3
nohz_full=2,3 rcu_nocbs=2,3 rcutree.dump_tree=1 rcuscale.shutdown=false
rcuscale.gp_async=true" -d

The problem is that the rcu_scale_writer() kthreads fail to set the
PF_NO_SETAFFINITY flags, which causes is_percpu_thread() to assume
that the kthread's affinity might change at any time, thus the BUG
noted above.

This commit therefore causes rcu_scale_writer() to set PF_NO_SETAFFINITY
in its kthread's ->flags field, thus preventing this BUG.

Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/rcuscale.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c
index 277a5bfb37d48..3ef02d4a81085 100644
--- a/kernel/rcu/rcuscale.c
+++ b/kernel/rcu/rcuscale.c
@@ -419,6 +419,7 @@ rcu_scale_writer(void *arg)
 	VERBOSE_SCALEOUT_STRING("rcu_scale_writer task started");
 	WARN_ON(!wdpp);
 	set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
+	current->flags |= PF_NO_SETAFFINITY;
 	sched_set_fifo_low(current);
 
 	if (holdoff)
-- 
2.31.1.189.g2e36527f23

[PATCH rcu 08/12] torture: Create kvm-check-branches.sh output in proper location

[Paul E. McKenney]

Currently, kvm-check-branches.sh causes each kvm.sh invocation create a
separate date-stamped directory, then after that invocation completes,
moves it into the *-group/NNNN directory.  This works, but makes it more
difficult to monitor an ongoing run.  This commit therefore uses the
kvm.sh --datestamp argument to make kvm.sh put the output in the right
place to start with, and also dispenses with the additional level of
datestamping.  (Those wanting datestamps can find them in the log files.)

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 .../selftests/rcutorture/bin/kvm-check-branches.sh    | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/tools/testing/selftests/rcutorture/bin/kvm-check-branches.sh b/tools/testing/selftests/rcutorture/bin/kvm-check-branches.sh
index f17000a2ccf1f..ed0ec7f0927e7 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm-check-branches.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm-check-branches.sh
@@ -35,7 +35,7 @@ then
 	exit 1
 fi
 
-# Remember where we started so that we can get back and the end.
+# Remember where we started so that we can get back at the end.
 curcommit="`git status | head -1 | awk '{ print $NF }'`"
 
 nfail=0
@@ -73,15 +73,10 @@ do
 		# Test the specified commit.
 		git checkout $i > $resdir/$ds/$idir/git-checkout.out 2>&1
 		echo git checkout return code: $? "(Commit $ntry: $i)"
-		kvm.sh --allcpus --duration 3 --trust-make > $resdir/$ds/$idir/kvm.sh.out 2>&1
+		kvm.sh --allcpus --duration 3 --trust-make --datestamp "$ds/$idir" > $resdir/$ds/$idir/kvm.sh.out 2>&1
 		ret=$?
 		echo kvm.sh return code $ret for commit $i from branch $gitbr
-
-		# Move the build products to their resting place.
-		runresdir="`grep -m 1 '^Results directory:' < $resdir/$ds/$idir/kvm.sh.out | sed -e 's/^Results directory://'`"
-		mv $runresdir $resdir/$ds/$idir
-		rrd="`echo $runresdir | sed -e 's,^.*/,,'`"
-		echo Run results: $resdir/$ds/$idir/$rrd
+		echo Run results: $resdir/$ds/$idir
 		if test "$ret" -ne 0
 		then
 			# Failure, so leave all evidence intact.
-- 
2.31.1.189.g2e36527f23

[PATCH rcu 0/12] Torture-test updates for v5.20

[Paul E. McKenney]

Hello!

This series provides torture-test updates, both C-language and scripting:

1.	Make kvm-remote.sh announce which system is being waited on.

2.	Change order of warning and trace dump, courtesy of Anna-Maria
	Behnsen.

3.	Simplify rcu_torture_read_exit_child() loop.

4.	Fix memory leak in rcu_test_debug_objects(), courtesy of Zqiang.

5.	Adjust to again produce debugging information.

6.	Make failure indication note reader-batch overflow.

7.	Fix smp_processor_id()-in-preemptible warnings, courtesy of
	Zqiang.

8.	Create kvm-check-branches.sh output in proper location.

9.	Fix ksoftirqd boosting timing and iteration, courtesy of Frederic
	Weisbecker.

10.	Handle failure of memory allocation functions, courtesy of
	Li Qiong.

11.	Flush printk() buffers before powering off.

12.	Convert test_lock spinlock to raw_spinlock, courtesy of Zqiang.

						Thanx, Paul

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

 b/kernel/rcu/rcuscale.c                                        |    1 
 b/kernel/rcu/rcutorture.c                                      |    3 
 b/kernel/rcu/refscale.c                                        |   18 +-
 b/kernel/torture.c                                             |    1 
 b/tools/testing/selftests/rcutorture/bin/kvm-check-branches.sh |   11 -
 b/tools/testing/selftests/rcutorture/bin/kvm-remote.sh         |    1 
 b/tools/testing/selftests/rcutorture/bin/kvm.sh                |    6 
 kernel/rcu/rcutorture.c                                        |   88 +++++-----
 8 files changed, 65 insertions(+), 64 deletions(-)

[PATCH rcu 09/12] rcutorture: Fix ksoftirqd boosting timing and iteration

[Paul E. McKenney]

From: Frederic Weisbecker <frederic@kernel.org>

The RCU priority boosting can fail in two situations:

1) If (nr_cpus= > maxcpus=), which means if the total number of CPUs
is higher than those brought online at boot, then torture_onoff() may
later bring up CPUs that weren't online on boot. Now since rcutorture
initialization only boosts the ksoftirqds of the CPUs that have been
set online on boot, the CPUs later set online by torture_onoff won't
benefit from the boost, making RCU priority boosting fail.

2) The ksoftirqd kthreads are boosted after the creation of
rcu_torture_boost() kthreads, which opens a window large enough for these
rcu_torture_boost() kthreads to wait (despite running at FIFO priority)
for ksoftirqds that are still running at SCHED_NORMAL priority.

The issues can trigger for example with:

	./kvm.sh --configs TREE01 --kconfig "CONFIG_RCU_BOOST=y"

	[   34.968561] rcu-torture: !!!
	[   34.968627] ------------[ cut here ]------------
	[   35.014054] WARNING: CPU: 4 PID: 114 at kernel/rcu/rcutorture.c:1979 rcu_torture_stats_print+0x5ad/0x610
	[   35.052043] Modules linked in:
	[   35.069138] CPU: 4 PID: 114 Comm: rcu_torture_sta Not tainted 5.18.0-rc1 #1
	[   35.096424] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.14.0-0-g155821a-rebuilt.opensuse.org 04/01/2014
	[   35.154570] RIP: 0010:rcu_torture_stats_print+0x5ad/0x610
	[   35.198527] Code: 63 1b 02 00 74 02 0f 0b 48 83 3d 35 63 1b 02 00 74 02 0f 0b 48 83 3d 21 63 1b 02 00 74 02 0f 0b 48 83 3d 0d 63 1b 02 00 74 02 <0f> 0b 83 eb 01 0f 8e ba fc ff ff 0f 0b e9 b3 fc ff f82
	[   37.251049] RSP: 0000:ffffa92a0050bdf8 EFLAGS: 00010202
	[   37.277320] rcu: De-offloading 8
	[   37.290367] RAX: 0000000000000000 RBX: 0000000000000001 RCX: 0000000000000001
	[   37.290387] RDX: 0000000000000000 RSI: 00000000ffffbfff RDI: 00000000ffffffff
	[   37.290398] RBP: 000000000000007b R08: 0000000000000000 R09: c0000000ffffbfff
	[   37.290407] R10: 000000000000002a R11: ffffa92a0050bc18 R12: ffffa92a0050be20
	[   37.290417] R13: ffffa92a0050be78 R14: 0000000000000000 R15: 000000000001bea0
	[   37.290427] FS:  0000000000000000(0000) GS:ffff96045eb00000(0000) knlGS:0000000000000000
	[   37.290448] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
	[   37.290460] CR2: 0000000000000000 CR3: 000000001dc0c000 CR4: 00000000000006e0
	[   37.290470] Call Trace:
	[   37.295049]  <TASK>
	[   37.295065]  ? preempt_count_add+0x63/0x90
	[   37.295095]  ? _raw_spin_lock_irqsave+0x12/0x40
	[   37.295125]  ? rcu_torture_stats_print+0x610/0x610
	[   37.295143]  rcu_torture_stats+0x29/0x70
	[   37.295160]  kthread+0xe3/0x110
	[   37.295176]  ? kthread_complete_and_exit+0x20/0x20
	[   37.295193]  ret_from_fork+0x22/0x30
	[   37.295218]  </TASK>

Fix this with boosting the ksoftirqds kthreads from the boosting
hotplug callback itself and before the boosting kthreads are created.

Fixes: ea6d962e80b6 ("rcutorture: Judge RCU priority boosting on grace periods, not callbacks")
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/rcutorture.c | 28 +++++++++++++---------------
 1 file changed, 13 insertions(+), 15 deletions(-)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 64ad5305829b6..b896987c21122 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -2076,6 +2076,19 @@ static int rcutorture_booster_init(unsigned int cpu)
 	if (boost_tasks[cpu] != NULL)
 		return 0;  /* Already created, nothing more to do. */
 
+	// Testing RCU priority boosting requires rcutorture do
+	// some serious abuse.  Counter this by running ksoftirqd
+	// at higher priority.
+	if (IS_BUILTIN(CONFIG_RCU_TORTURE_TEST)) {
+		struct sched_param sp;
+		struct task_struct *t;
+
+		t = per_cpu(ksoftirqd, cpu);
+		WARN_ON_ONCE(!t);
+		sp.sched_priority = 2;
+		sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
+	}
+
 	/* Don't allow time recalculation while creating a new task. */
 	mutex_lock(&boost_mutex);
 	rcu_torture_disable_rt_throttle();
@@ -3324,21 +3337,6 @@ rcu_torture_init(void)
 		rcutor_hp = firsterr;
 		if (torture_init_error(firsterr))
 			goto unwind;
-
-		// Testing RCU priority boosting requires rcutorture do
-		// some serious abuse.  Counter this by running ksoftirqd
-		// at higher priority.
-		if (IS_BUILTIN(CONFIG_RCU_TORTURE_TEST)) {
-			for_each_online_cpu(cpu) {
-				struct sched_param sp;
-				struct task_struct *t;
-
-				t = per_cpu(ksoftirqd, cpu);
-				WARN_ON_ONCE(!t);
-				sp.sched_priority = 2;
-				sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
-			}
-		}
 	}
 	shutdown_jiffies = jiffies + shutdown_secs * HZ;
 	firsterr = torture_shutdown_init(shutdown_secs, rcu_torture_cleanup);
-- 
2.31.1.189.g2e36527f23

[PATCH rcu 10/12] rcutorture: Handle failure of memory allocation functions

[Paul E. McKenney]

From: Li Qiong <liqiong@nfschina.com>

This commit adds warnings for allocation failure during the mem_dump_obj()
tests.  It also terminates these tests upon such failure.

Signed-off-by: Li Qiong <liqiong@nfschina.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/rcutorture.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index b896987c21122..e2db5d6beabaa 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1991,7 +1991,13 @@ static void rcu_torture_mem_dump_obj(void)
 	static int z;
 
 	kcp = kmem_cache_create("rcuscale", 136, 8, SLAB_STORE_USER, NULL);
+	if (WARN_ON_ONCE(!kcp))
+		return;
 	rhp = kmem_cache_alloc(kcp, GFP_KERNEL);
+	if (WARN_ON_ONCE(!rhp)) {
+		kmem_cache_destroy(kcp);
+		return;
+	}
 	pr_alert("mem_dump_obj() slab test: rcu_torture_stats = %px, &rhp = %px, rhp = %px, &z = %px\n", stats_task, &rhp, rhp, &z);
 	pr_alert("mem_dump_obj(ZERO_SIZE_PTR):");
 	mem_dump_obj(ZERO_SIZE_PTR);
@@ -2008,6 +2014,8 @@ static void rcu_torture_mem_dump_obj(void)
 	kmem_cache_free(kcp, rhp);
 	kmem_cache_destroy(kcp);
 	rhp = kmalloc(sizeof(*rhp), GFP_KERNEL);
+	if (WARN_ON_ONCE(!rhp))
+		return;
 	pr_alert("mem_dump_obj() kmalloc test: rcu_torture_stats = %px, &rhp = %px, rhp = %px\n", stats_task, &rhp, rhp);
 	pr_alert("mem_dump_obj(kmalloc %px):", rhp);
 	mem_dump_obj(rhp);
@@ -2015,6 +2023,8 @@ static void rcu_torture_mem_dump_obj(void)
 	mem_dump_obj(&rhp->func);
 	kfree(rhp);
 	rhp = vmalloc(4096);
+	if (WARN_ON_ONCE(!rhp))
+		return;
 	pr_alert("mem_dump_obj() vmalloc test: rcu_torture_stats = %px, &rhp = %px, rhp = %px\n", stats_task, &rhp, rhp);
 	pr_alert("mem_dump_obj(vmalloc %px):", rhp);
 	mem_dump_obj(rhp);
-- 
2.31.1.189.g2e36527f23

[PATCH rcu 11/12] torture: Flush printk() buffers before powering off

[Paul E. McKenney]

The rcutorture test suite produces quite a bit of console output
at the end of a test.  This means that the new printk() kthreads
are likely to be in the process of flushing output at the time of
the torture_shutdown() function's call to kernel_power_off().

This commit therefore invokes pr_flush(1000, true) to flush this
pending console output before invoking kernel_power_off().

Fixes: 8e274732115f ("printk: extend console_lock for per-console locking")
Cc: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/torture.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/torture.c b/kernel/torture.c
index 789aeb0e1159c..6d7b282fbb5f8 100644
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -651,6 +651,7 @@ static int torture_shutdown(void *arg)
 		VERBOSE_TOROUT_STRING("No torture_shutdown_hook(), skipping.");
 	if (ftrace_dump_at_shutdown)
 		rcu_ftrace_dump(DUMP_ALL);
+	pr_flush(1000, true);
 	kernel_power_off();	/* Shut down the system. */
 	return 0;
 }
-- 
2.31.1.189.g2e36527f23

[PATCH rcu 12/12] refscale: Convert test_lock spinlock to raw_spinlock

[Paul E. McKenney]

From: Zqiang <qiang1.zhang@intel.com>

In kernels built with CONFIG_PREEMPT_RT=y, spinlocks are replaced by
rt_mutex, which can sleep.  This means that acquiring a non-raw spinlock
in a critical section where preemption is disabled can trigger the
following BUG:

BUG: scheduling while atomic: ref_scale_reade/76/0x00000002
Preemption disabled at:
ref_lock_section+0x16/0x80
Call Trace:
<TASK>
dump_stack_lvl+0x5b/0x82
dump_stack+0x10/0x12
__schedule_bug.cold+0x9c/0xad
__schedule+0x839/0xc00
schedule_rtlock+0x22/0x40
rtlock_slowlock_locked+0x460/0x1350
rt_spin_lock+0x61/0xe0
ref_lock_section+0x29/0x80
rcu_scale_one_reader+0x52/0x60
ref_scale_reader+0x28d/0x490
kthread+0x128/0x150
ret_from_fork+0x22/0x30
</TASK>

This commit therefore converts spinlock to raw_spinlock.

Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/refscale.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
index 909644abee67f..435c884c02b5c 100644
--- a/kernel/rcu/refscale.c
+++ b/kernel/rcu/refscale.c
@@ -385,7 +385,7 @@ static struct ref_scale_ops rwsem_ops = {
 };
 
 // Definitions for global spinlock
-static DEFINE_SPINLOCK(test_lock);
+static DEFINE_RAW_SPINLOCK(test_lock);
 
 static void ref_lock_section(const int nloops)
 {
@@ -393,8 +393,8 @@ static void ref_lock_section(const int nloops)
 
 	preempt_disable();
 	for (i = nloops; i >= 0; i--) {
-		spin_lock(&test_lock);
-		spin_unlock(&test_lock);
+		raw_spin_lock(&test_lock);
+		raw_spin_unlock(&test_lock);
 	}
 	preempt_enable();
 }
@@ -405,9 +405,9 @@ static void ref_lock_delay_section(const int nloops, const int udl, const int nd
 
 	preempt_disable();
 	for (i = nloops; i >= 0; i--) {
-		spin_lock(&test_lock);
+		raw_spin_lock(&test_lock);
 		un_delay(udl, ndl);
-		spin_unlock(&test_lock);
+		raw_spin_unlock(&test_lock);
 	}
 	preempt_enable();
 }
@@ -427,8 +427,8 @@ static void ref_lock_irq_section(const int nloops)
 
 	preempt_disable();
 	for (i = nloops; i >= 0; i--) {
-		spin_lock_irqsave(&test_lock, flags);
-		spin_unlock_irqrestore(&test_lock, flags);
+		raw_spin_lock_irqsave(&test_lock, flags);
+		raw_spin_unlock_irqrestore(&test_lock, flags);
 	}
 	preempt_enable();
 }
@@ -440,9 +440,9 @@ static void ref_lock_irq_delay_section(const int nloops, const int udl, const in
 
 	preempt_disable();
 	for (i = nloops; i >= 0; i--) {
-		spin_lock_irqsave(&test_lock, flags);
+		raw_spin_lock_irqsave(&test_lock, flags);
 		un_delay(udl, ndl);
-		spin_unlock_irqrestore(&test_lock, flags);
+		raw_spin_unlock_irqrestore(&test_lock, flags);
 	}
 	preempt_enable();
 }
-- 
2.31.1.189.g2e36527f23

Re: [PATCH rcu 11/12] torture: Flush printk() buffers before powering off

[John Ogness]

On 2022-06-20, "Paul E. McKenney" <paulmck@kernel.org> wrote:
> The rcutorture test suite produces quite a bit of console output
> at the end of a test.  This means that the new printk() kthreads
> are likely to be in the process of flushing output at the time of
> the torture_shutdown() function's call to kernel_power_off().
>
> This commit therefore invokes pr_flush(1000, true) to flush this
> pending console output before invoking kernel_power_off().
>
> Fixes: 8e274732115f ("printk: extend console_lock for per-console locking")
> Cc: John Ogness <john.ogness@linutronix.de>
> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Reviewed-by: John Ogness <john.ogness@linutronix.de>

Re: [PATCH rcu 11/12] torture: Flush printk() buffers before powering off

[Paul E. McKenney]

On Tue, Jun 21, 2022 at 01:29:04AM +0206, John Ogness wrote:
> On 2022-06-20, "Paul E. McKenney" <paulmck@kernel.org> wrote:
> > The rcutorture test suite produces quite a bit of console output
> > at the end of a test.  This means that the new printk() kthreads
> > are likely to be in the process of flushing output at the time of
> > the torture_shutdown() function's call to kernel_power_off().
> >
> > This commit therefore invokes pr_flush(1000, true) to flush this
> > pending console output before invoking kernel_power_off().
> >
> > Fixes: 8e274732115f ("printk: extend console_lock for per-console locking")
> > Cc: John Ogness <john.ogness@linutronix.de>
> > Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
> 
> Reviewed-by: John Ogness <john.ogness@linutronix.de>

Thank you, John!

But given Petr's and your recent changes that are now in mainline, is
this still really needed?  (Tests now pass without it, though tests can
of course be misleading.)

							Thanx, Paul

Re: [PATCH rcu 11/12] torture: Flush printk() buffers before powering off

[John Ogness]

On 2022-06-20, "Paul E. McKenney" <paulmck@kernel.org> wrote:
> But given Petr's and your recent changes that are now in mainline, is
> this still really needed?  (Tests now pass without it, though tests can
> of course be misleading.)

If all you are interested is if your rcutorture testing was successful,
then I would keep this change. Then, no matter what the kernel does
afterwards, you have your test results.

However, the kernel should correctly shutdown and it should flush the
kernel buffers on shutdown or crash. (It is a kernel bug otherwise.) So
if you also want to implicitly test this (non-rcutorture) functionality,
then you should not use this patch.

John Ogness

Re: [PATCH rcu 11/12] torture: Flush printk() buffers before powering off

[Paul E. McKenney]

On Tue, Jun 21, 2022 at 10:15:29AM +0206, John Ogness wrote:
> On 2022-06-20, "Paul E. McKenney" <paulmck@kernel.org> wrote:
> > But given Petr's and your recent changes that are now in mainline, is
> > this still really needed?  (Tests now pass without it, though tests can
> > of course be misleading.)
> 
> If all you are interested is if your rcutorture testing was successful,
> then I would keep this change. Then, no matter what the kernel does
> afterwards, you have your test results.
> 
> However, the kernel should correctly shutdown and it should flush the
> kernel buffers on shutdown or crash. (It is a kernel bug otherwise.) So
> if you also want to implicitly test this (non-rcutorture) functionality,
> then you should not use this patch.

Why not both?  ;-)

The patch below will cause rcutorture to implicitly test this
functionality, unless told otherwise, for example, by using the
--bootargs "torture.printk_shutdown_bug_workaround" kvm.sh
argument.

Thoughts?

							Thanx, Paul

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

commit 204bf1e2a5a2fb68c15b4b64793ad0896db6f705
Author: Paul E. McKenney <paulmck@kernel.org>
Date:   Tue Jun 21 11:02:25 2022 -0700

    torture: Optionally flush printk() buffers before powering off
    
    The rcutorture test suite produces quite a bit of console output at
    the end of a test.  This means that the new-in-2022 printk() kthreads
    are likely to be in the process of flushing output at the time of the
    torture_shutdown() function's call to kernel_power_off().  Normally,
    rcutorture relies on printk() to flush any pending output upon shutdown,
    the better to detect bugs in this area, for example, the one introduced
    by 8e274732115f ("printk: extend console_lock for per-console locking").
    However, once such a bug is detected and reported, it is necessary to
    test the rest of the system, without noise from the already-reported bug.
    
    This commit therefore adds a torture.printk_shutdown_bug_workaround
    kernel parameter, which causes torture_shutdown() to invoke pr_flush(),
    and print an informative message on the console, immediately before
    invoking kernel_power_off().  When this kernel parameter is not specified,
    it is up to printk() to flush its own buffers.
    
    Suggested-by: John Ogness <john.ogness@linutronix.de>
    Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index d8de18d8f8875..652f49c4e5990 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -6045,6 +6045,12 @@
 			are running concurrently, especially on systems
 			with rotating-rust storage.
 
+	torture.printk_shutdown_bug_workaround= [KNL]
+			Execute pr_flush(1000, true) just before invoking
+			kernel_power_off() to work around any bugs that
+			might prevent printk() from flushing its buffers
+			at shutdown time.
+
 	torture.verbose_sleep_frequency= [KNL]
 			Specifies how many verbose printk()s should be
 			emitted between each sleep.  The default of zero
diff --git a/kernel/torture.c b/kernel/torture.c
index 789aeb0e1159c..7cd2016b02076 100644
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -48,6 +48,9 @@ module_param(disable_onoff_at_boot, bool, 0444);
 static bool ftrace_dump_at_shutdown;
 module_param(ftrace_dump_at_shutdown, bool, 0444);
 
+static bool printk_shutdown_bug_workaround;
+module_param(printk_shutdown_bug_workaround, bool, 0444);
+
 static int verbose_sleep_frequency;
 module_param(verbose_sleep_frequency, int, 0444);
 
@@ -651,6 +654,10 @@ static int torture_shutdown(void *arg)
 		VERBOSE_TOROUT_STRING("No torture_shutdown_hook(), skipping.");
 	if (ftrace_dump_at_shutdown)
 		rcu_ftrace_dump(DUMP_ALL);
+	if (printk_shutdown_bug_workaround) {
+		pr_info("%s: Flushing printk() buffers at power-down time.\n", __func__);
+		pr_flush(1000, true);
+	}
 	kernel_power_off();	/* Shut down the system. */
 	return 0;
 }

Re: [PATCH rcu 11/12] torture: Flush printk() buffers before powering off

[John Ogness]

On 2022-06-21, "Paul E. McKenney" <paulmck@kernel.org> wrote:
> The patch below will cause rcutorture to implicitly test this
> functionality, unless told otherwise, for example, by using the
> --bootargs "torture.printk_shutdown_bug_workaround" kvm.sh
> argument.
>
> Thoughts?

I feel like this is dirtying the torture.* bootarg namespace a
bit. Also, I am not sure how useful it is as a dynamic option. I assume
that users would generally avoid using it, so its very existence might
just be more noise in the documentation and code. It is an unusual
feature:

"In case some bug shows up, here is a flag to avoid it."

I personally would just drop the patch and rely on a correctly
functional kernel. But I am also not an rcutorture user. If _you_ think
that such a flag is useful, feel free to include the patch.

> commit 204bf1e2a5a2fb68c15b4b64793ad0896db6f705
> Author: Paul E. McKenney <paulmck@kernel.org>
> Date:   Tue Jun 21 11:02:25 2022 -0700
>
>     torture: Optionally flush printk() buffers before powering off
>     
>     The rcutorture test suite produces quite a bit of console output at
>     the end of a test.  This means that the new-in-2022 printk() kthreads
>     are likely to be in the process of flushing output at the time of the
>     torture_shutdown() function's call to kernel_power_off().  Normally,
>     rcutorture relies on printk() to flush any pending output upon shutdown,
>     the better to detect bugs in this area, for example, the one introduced
>     by 8e274732115f ("printk: extend console_lock for per-console locking").
>     However, once such a bug is detected and reported, it is necessary to
>     test the rest of the system, without noise from the already-reported bug.
>     
>     This commit therefore adds a torture.printk_shutdown_bug_workaround
>     kernel parameter, which causes torture_shutdown() to invoke pr_flush(),
>     and print an informative message on the console, immediately before
>     invoking kernel_power_off().  When this kernel parameter is not specified,
>     it is up to printk() to flush its own buffers.
>     
>     Suggested-by: John Ogness <john.ogness@linutronix.de>
>     Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Reviewed-by: John Ogness <john.ogness@linutronix.de>

Re: [PATCH rcu 11/12] torture: Flush printk() buffers before powering off

[Paul E. McKenney]

On Tue, Jun 21, 2022 at 10:58:27PM +0206, John Ogness wrote:
> On 2022-06-21, "Paul E. McKenney" <paulmck@kernel.org> wrote:
> > The patch below will cause rcutorture to implicitly test this
> > functionality, unless told otherwise, for example, by using the
> > --bootargs "torture.printk_shutdown_bug_workaround" kvm.sh
> > argument.
> >
> > Thoughts?
> 
> I feel like this is dirtying the torture.* bootarg namespace a
> bit. Also, I am not sure how useful it is as a dynamic option. I assume
> that users would generally avoid using it, so its very existence might
> just be more noise in the documentation and code. It is an unusual
> feature:
> 
> "In case some bug shows up, here is a flag to avoid it."
> 
> I personally would just drop the patch and rely on a correctly
> functional kernel. But I am also not an rcutorture user. If _you_ think
> that such a flag is useful, feel free to include the patch.

Fair points!

The main value to me is to avoid me having to pile through code to relearn
the incantation pr_flush(1000, true).  Which, now that you mention it,
could be dealt with by adding a comment:

	// pr_flush(1000, true); // If needed to flush printk() buffers.

This definitely will not go into the upcoming merge window, so there is
plenty of time to give it some thought.

> > commit 204bf1e2a5a2fb68c15b4b64793ad0896db6f705
> > Author: Paul E. McKenney <paulmck@kernel.org>
> > Date:   Tue Jun 21 11:02:25 2022 -0700
> >
> >     torture: Optionally flush printk() buffers before powering off
> >     
> >     The rcutorture test suite produces quite a bit of console output at
> >     the end of a test.  This means that the new-in-2022 printk() kthreads
> >     are likely to be in the process of flushing output at the time of the
> >     torture_shutdown() function's call to kernel_power_off().  Normally,
> >     rcutorture relies on printk() to flush any pending output upon shutdown,
> >     the better to detect bugs in this area, for example, the one introduced
> >     by 8e274732115f ("printk: extend console_lock for per-console locking").
> >     However, once such a bug is detected and reported, it is necessary to
> >     test the rest of the system, without noise from the already-reported bug.
> >     
> >     This commit therefore adds a torture.printk_shutdown_bug_workaround
> >     kernel parameter, which causes torture_shutdown() to invoke pr_flush(),
> >     and print an informative message on the console, immediately before
> >     invoking kernel_power_off().  When this kernel parameter is not specified,
> >     it is up to printk() to flush its own buffers.
> >     
> >     Suggested-by: John Ogness <john.ogness@linutronix.de>
> >     Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
> 
> Reviewed-by: John Ogness <john.ogness@linutronix.de>

Thank you!

							Thanx, Paul