[PATCH tip/core/rcu 01/23] torture: Remove qemu dependency on EFI firmware

[PATCH tip/core/rcu 01/23] torture: Remove qemu dependency on EFI firmware

[paulmck]

From: "Paul E. McKenney" <paulmck@kernel.org>

On some (probably misconfigured) systems, the torture-test scripting
will cause qemu to complain about missing EFI firmware, often because
qemu is trying to traverse broken symbolic links to find that firmware.
Which is a bit silly given that the default torture-test guest OS has
but a single binary for its userspace, and thus is unlikely to do much
in the way of networking in any case.

This commit therefore avoids such problems by specifying "-net none"
to qemu unless the TORTURE_QEMU_INTERACTIVE environment variable is set
(for example, by having specified "--interactive" to kvm.sh), in which
case "-net nic -net user" is specified to qemu instead.  Either choice
may be overridden by specifying the "-net" argument of your choice to
the kvm.sh "--qemu-args" parameter.

Link: https://lore.kernel.org/lkml/20190701141403.GA246562@google.com
Reported-by: Joel Fernandes <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 tools/testing/selftests/rcutorture/bin/functions.sh | 21 ++++++++++++++++++---
 .../selftests/rcutorture/bin/kvm-test-1-run.sh      |  1 +
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/rcutorture/bin/functions.sh b/tools/testing/selftests/rcutorture/bin/functions.sh
index 1281022..436b154 100644
--- a/tools/testing/selftests/rcutorture/bin/functions.sh
+++ b/tools/testing/selftests/rcutorture/bin/functions.sh
@@ -215,9 +215,6 @@ identify_qemu_args () {
 		then
 			echo -device spapr-vlan,netdev=net0,mac=$TORTURE_QEMU_MAC
 			echo -netdev bridge,br=br0,id=net0
-		elif test -n "$TORTURE_QEMU_INTERACTIVE"
-		then
-			echo -net nic -net user
 		fi
 		;;
 	esac
@@ -275,3 +272,21 @@ specify_qemu_cpus () {
 		esac
 	fi
 }
+
+# specify_qemu_net qemu-args
+#
+# Appends a string containing "-net none" to qemu-args, unless the incoming
+# qemu-args already contains "-smp" or unless the TORTURE_QEMU_INTERACTIVE
+# environment variable is set, in which case the string that is be added is
+# instead "-net nic -net user".
+specify_qemu_net () {
+	if echo $1 | grep -q -e -net
+	then
+		echo $1
+	elif test -n "$TORTURE_QEMU_INTERACTIVE"
+	then
+		echo $1 -net nic -net user
+	else
+		echo $1 -net none
+	fi
+}
diff --git a/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh b/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
index 6ff611c..1b9aebd 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
@@ -141,6 +141,7 @@ then
 	cpu_count=$TORTURE_ALLOTED_CPUS
 fi
 qemu_args="`specify_qemu_cpus "$QEMU" "$qemu_args" "$cpu_count"`"
+qemu_args="`specify_qemu_net "$qemu_args"`"
 
 # Generate architecture-specific and interaction-specific qemu arguments
 qemu_args="$qemu_args `identify_qemu_args "$QEMU" "$resdir/console.log"`"
-- 
2.9.5

[PATCH tip/core/rcu 0/23] Torture-test updates for v5.9

[Paul E. McKenney]

Hello!

This series provides torture-test updates:

1.	 Remove qemu dependency on EFI firmware.

2.	Add script to smoke-test commits in a branch.

3.	Use true and false to assign to bool variables, courtesy of Zou Wei.

4.	Add races with task-exit processing.

5.	Set configfile variable to current scenario.

6.	Handle non-statistic bang-string error messages.

7.	NULL rcu_torture_current earlier in cleanup code.

8.	Remove whitespace from identify_qemu_vcpus output.

9.	Add --allcpus argument to the kvm.sh script.

10.	rcu/rcutorture: Replace 0 with false, courtesy of Jules Irenge.

11.	Create qemu-cmd in --buildonly runs.

12.	Add a stop-run capability.

13.	Abstract out console-log error detection.

14.	Check for unwatched readers.

15.	Pass --kmake-arg to all make invocations, courtesy of Marco Elver.

16.	Correctly summarize build-only runs.

17.	Improve diagnostic for KCSAN-incapable compilers.

18.	Add more tracing crib notes to kvm.sh.

19.	Add kvm-tranform.sh script for qemu-cmd files.

20.	Dump ftrace at shutdown only if requested.

21.	Avoid duplicate specification of qemu command.

22.	Remove obsolete "cd $KVM".

23.	Remove KCSAN stubs.

							Thanx, Paul

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

 Documentation/admin-guide/kernel-parameters.txt              |   21 +
 include/linux/torture.h                                      |    5 
 kernel/locking/locktorture.c                                 |   14 -
 kernel/rcu/rcutorture.c                                      |  130 +++++++++--
 kernel/torture.c                                             |    6 
 tools/testing/selftests/rcutorture/bin/configinit.sh         |    4 
 tools/testing/selftests/rcutorture/bin/console-badness.sh    |   16 +
 tools/testing/selftests/rcutorture/bin/functions.sh          |   23 +
 tools/testing/selftests/rcutorture/bin/jitter.sh             |    6 
 tools/testing/selftests/rcutorture/bin/kvm-build.sh          |    6 
 tools/testing/selftests/rcutorture/bin/kvm-check-branches.sh |  108 +++++++++
 tools/testing/selftests/rcutorture/bin/kvm-recheck.sh        |   20 +
 tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh     |   27 +-
 tools/testing/selftests/rcutorture/bin/kvm-transform.sh      |   51 ++++
 tools/testing/selftests/rcutorture/bin/kvm.sh                |   10 
 tools/testing/selftests/rcutorture/bin/parse-console.sh      |   23 +
 16 files changed, 419 insertions(+), 51 deletions(-)

[PATCH tip/core/rcu 02/23] torture: Add script to smoke-test commits in a branch

[paulmck]

From: "Paul E. McKenney" <paulmck@kernel.org>

This commit adds a kvm-check-branches.sh script that takes a list
of commits and commit ranges and runs a short rcutorture test on all
scenarios on each specified commit.  A summary is printed at the end, and
the script returns success if all rcutorture runs completed without error.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 .../selftests/rcutorture/bin/kvm-check-branches.sh | 108 +++++++++++++++++++++
 1 file changed, 108 insertions(+)
 create mode 100755 tools/testing/selftests/rcutorture/bin/kvm-check-branches.sh

diff --git a/tools/testing/selftests/rcutorture/bin/kvm-check-branches.sh b/tools/testing/selftests/rcutorture/bin/kvm-check-branches.sh
new file mode 100755
index 0000000..6e65c13
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/bin/kvm-check-branches.sh
@@ -0,0 +1,108 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0+
+#
+# Run a group of kvm.sh tests on the specified commits.  This currently
+# unconditionally does three-minute runs on each scenario in CFLIST,
+# taking advantage of all available CPUs and trusting the "make" utility.
+# In the short term, adjustments can be made by editing this script and
+# CFLIST.  If some adjustments appear to have ongoing value, this script
+# might grow some command-line arguments.
+#
+# Usage: kvm-check-branches.sh commit1 commit2..commit3 commit4 ...
+#
+# This script considers its arguments one at a time.  If more elaborate
+# specification of commits is needed, please use "git rev-list" to
+# produce something that this simple script can understand.  The reason
+# for retaining the simplicity is that it allows the user to more easily
+# see which commit came from which branch.
+#
+# This script creates a yyyy.mm.dd-hh.mm.ss-group entry in the "res"
+# directory.  The calls to kvm.sh create the usual entries, but this script
+# moves them under the yyyy.mm.dd-hh.mm.ss-group entry, each in its own
+# directory numbered in run order, that is, "0001", "0002", and so on.
+# For successful runs, the large build artifacts are removed.  Doing this
+# reduces the disk space required by about two orders of magnitude for
+# successful runs.
+#
+# Copyright (C) Facebook, 2020
+#
+# Authors: Paul E. McKenney <paulmck@kernel.org>
+
+if ! git status > /dev/null 2>&1
+then
+	echo '!!!' This script needs to run in a git archive. 1>&2
+	echo '!!!' Giving up. 1>&2
+	exit 1
+fi
+
+# Remember where we started so that we can get back and the end.
+curcommit="`git status | head -1 | awk '{ print $NF }'`"
+
+nfail=0
+ntry=0
+resdir="tools/testing/selftests/rcutorture/res"
+ds="`date +%Y.%m.%d-%H.%M.%S`-group"
+if ! test -e $resdir
+then
+	mkdir $resdir || :
+fi
+mkdir $resdir/$ds
+echo Results directory: $resdir/$ds
+
+KVM="`pwd`/tools/testing/selftests/rcutorture"; export KVM
+PATH=${KVM}/bin:$PATH; export PATH
+. functions.sh
+cpus="`identify_qemu_vcpus`"
+echo Using up to $cpus CPUs.
+
+# Each pass through this loop does one command-line argument.
+for gitbr in $@
+do
+	echo ' --- git branch ' $gitbr
+
+	# Each pass through this loop tests one commit.
+	for i in `git rev-list "$gitbr"`
+	do
+		ntry=`expr $ntry + 1`
+		idir=`awk -v ntry="$ntry" 'END { printf "%04d", ntry; }' < /dev/null`
+		echo ' --- commit ' $i from branch $gitbr
+		date
+		mkdir $resdir/$ds/$idir
+		echo $gitbr > $resdir/$ds/$idir/gitbr
+		echo $i >> $resdir/$ds/$idir/gitbr
+
+		# 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 --cpus $cpus --duration 3 --trust-make > $resdir/$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
+		if test "$ret" -ne 0
+		then
+			# Failure, so leave all evidence intact.
+			nfail=`expr $nfail + 1`
+		else
+			# Success, so remove large files to save about 1GB.
+			( cd $resdir/$ds/$idir/$rrd; rm -f */vmlinux */bzImage */System.map */Module.symvers )
+		fi
+	done
+done
+date
+
+# Go back to the original commit.
+git checkout "$curcommit"
+
+if test $nfail -ne 0
+then
+	echo '!!! ' $nfail failures in $ntry 'runs!!!'
+	exit 1
+else
+	echo No failures in $ntry runs.
+	exit 0
+fi
-- 
2.9.5

[PATCH tip/core/rcu 03/23] locktorture: Use true and false to assign to bool variables

[paulmck]

From: Zou Wei <zou_wei@huawei.com>

This commit fixes the following coccicheck warnings:

kernel/locking/locktorture.c:689:6-10: WARNING: Assignment of 0/1 to bool variable
kernel/locking/locktorture.c:907:2-20: WARNING: Assignment of 0/1 to bool variable
kernel/locking/locktorture.c:938:3-20: WARNING: Assignment of 0/1 to bool variable
kernel/locking/locktorture.c:668:2-19: WARNING: Assignment of 0/1 to bool variable
kernel/locking/locktorture.c:674:2-19: WARNING: Assignment of 0/1 to bool variable
kernel/locking/locktorture.c:634:2-20: WARNING: Assignment of 0/1 to bool variable
kernel/locking/locktorture.c:640:2-20: WARNING: Assignment of 0/1 to bool variable

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zou Wei <zou_wei@huawei.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/locking/locktorture.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
index 5efbfc6..8ff6f50 100644
--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -631,13 +631,13 @@ static int lock_torture_writer(void *arg)
 		cxt.cur_ops->writelock();
 		if (WARN_ON_ONCE(lock_is_write_held))
 			lwsp->n_lock_fail++;
-		lock_is_write_held = 1;
+		lock_is_write_held = true;
 		if (WARN_ON_ONCE(lock_is_read_held))
 			lwsp->n_lock_fail++; /* rare, but... */
 
 		lwsp->n_lock_acquired++;
 		cxt.cur_ops->write_delay(&rand);
-		lock_is_write_held = 0;
+		lock_is_write_held = false;
 		cxt.cur_ops->writeunlock();
 
 		stutter_wait("lock_torture_writer");
@@ -665,13 +665,13 @@ static int lock_torture_reader(void *arg)
 			schedule_timeout_uninterruptible(1);
 
 		cxt.cur_ops->readlock();
-		lock_is_read_held = 1;
+		lock_is_read_held = true;
 		if (WARN_ON_ONCE(lock_is_write_held))
 			lrsp->n_lock_fail++; /* rare, but... */
 
 		lrsp->n_lock_acquired++;
 		cxt.cur_ops->read_delay(&rand);
-		lock_is_read_held = 0;
+		lock_is_read_held = false;
 		cxt.cur_ops->readunlock();
 
 		stutter_wait("lock_torture_reader");
@@ -686,7 +686,7 @@ static int lock_torture_reader(void *arg)
 static void __torture_print_stats(char *page,
 				  struct lock_stress_stats *statp, bool write)
 {
-	bool fail = 0;
+	bool fail = false;
 	int i, n_stress;
 	long max = 0, min = statp ? statp[0].n_lock_acquired : 0;
 	long long sum = 0;
@@ -904,7 +904,7 @@ static int __init lock_torture_init(void)
 
 	/* Initialize the statistics so that each run gets its own numbers. */
 	if (nwriters_stress) {
-		lock_is_write_held = 0;
+		lock_is_write_held = false;
 		cxt.lwsa = kmalloc_array(cxt.nrealwriters_stress,
 					 sizeof(*cxt.lwsa),
 					 GFP_KERNEL);
@@ -935,7 +935,7 @@ static int __init lock_torture_init(void)
 		}
 
 		if (nreaders_stress) {
-			lock_is_read_held = 0;
+			lock_is_read_held = false;
 			cxt.lrsa = kmalloc_array(cxt.nrealreaders_stress,
 						 sizeof(*cxt.lrsa),
 						 GFP_KERNEL);
-- 
2.9.5

[PATCH tip/core/rcu 04/23] rcutorture: Add races with task-exit processing

[paulmck]

From: "Paul E. McKenney" <paulmck@kernel.org>

Several variants of Linux-kernel RCU interact with task-exit processing,
including preemptible RCU, Tasks RCU, and Tasks Trace RCU.  This commit
therefore adds testing of this interaction to rcutorture by adding
rcutorture.read_exit_burst and rcutorture.read_exit_delay kernel-boot
parameters.  These kernel parameters control the frequency and spacing
of special read-then-exit kthreads that are spawned.

[ paulmck: Apply feedback from Dan Carpenter's static checker. ]
[ paulmck: Reduce latency to avoid false-positive shutdown hangs. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 Documentation/admin-guide/kernel-parameters.txt |  14 +++
 include/linux/torture.h                         |   5 ++
 kernel/rcu/rcutorture.c                         | 112 +++++++++++++++++++++++-
 3 files changed, 128 insertions(+), 3 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index fb95fad..a0dcc92 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4258,6 +4258,20 @@
 			Set time (jiffies) between CPU-hotplug operations,
 			or zero to disable CPU-hotplug testing.
 
+	rcutorture.read_exit= [KNL]
+			Set the number of read-then-exit kthreads used
+			to test the interaction of RCU updaters and
+			task-exit processing.
+
+	rcutorture.read_exit_burst= [KNL]
+			The number of times in a given read-then-exit
+			episode that a set of read-then-exit kthreads
+			is spawned.
+
+	rcutorture.read_exit_delay= [KNL]
+			The delay, in seconds, between successive
+			read-then-exit testing episodes.
+
 	rcutorture.shuffle_interval= [KNL]
 			Set task-shuffle interval (s).  Shuffling tasks
 			allows some CPUs to go into dyntick-idle mode
diff --git a/include/linux/torture.h b/include/linux/torture.h
index 629b66e..7f65bd1 100644
--- a/include/linux/torture.h
+++ b/include/linux/torture.h
@@ -55,6 +55,11 @@ struct torture_random_state {
 #define DEFINE_TORTURE_RANDOM_PERCPU(name) \
 	DEFINE_PER_CPU(struct torture_random_state, name)
 unsigned long torture_random(struct torture_random_state *trsp);
+static inline void torture_random_init(struct torture_random_state *trsp)
+{
+	trsp->trs_state = 0;
+	trsp->trs_count = 0;
+}
 
 /* Task shuffler, which causes CPUs to occasionally go idle. */
 void torture_shuffle_task_register(struct task_struct *tp);
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index efb792e..2621a33 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -109,6 +109,10 @@ torture_param(int, object_debug, 0,
 torture_param(int, onoff_holdoff, 0, "Time after boot before CPU hotplugs (s)");
 torture_param(int, onoff_interval, 0,
 	     "Time between CPU hotplugs (jiffies), 0=disable");
+torture_param(int, read_exit_delay, 13,
+	      "Delay between read-then-exit episodes (s)");
+torture_param(int, read_exit_burst, 16,
+	      "# of read-then-exit bursts per episode, zero to disable");
 torture_param(int, shuffle_interval, 3, "Number of seconds between shuffles");
 torture_param(int, shutdown_secs, 0, "Shutdown time (s), <= zero to disable.");
 torture_param(int, stall_cpu, 0, "Stall duration (s), zero to disable.");
@@ -146,6 +150,7 @@ static struct task_struct *stall_task;
 static struct task_struct *fwd_prog_task;
 static struct task_struct **barrier_cbs_tasks;
 static struct task_struct *barrier_task;
+static struct task_struct *read_exit_task;
 
 #define RCU_TORTURE_PIPE_LEN 10
 
@@ -177,6 +182,7 @@ static long n_rcu_torture_boosts;
 static atomic_long_t n_rcu_torture_timers;
 static long n_barrier_attempts;
 static long n_barrier_successes; /* did rcu_barrier test succeed? */
+static unsigned long n_read_exits;
 static struct list_head rcu_torture_removed;
 static unsigned long shutdown_jiffies;
 
@@ -1539,10 +1545,11 @@ rcu_torture_stats_print(void)
 		n_rcu_torture_boosts,
 		atomic_long_read(&n_rcu_torture_timers));
 	torture_onoff_stats();
-	pr_cont("barrier: %ld/%ld:%ld\n",
+	pr_cont("barrier: %ld/%ld:%ld ",
 		data_race(n_barrier_successes),
 		data_race(n_barrier_attempts),
 		data_race(n_rcu_torture_barrier_error));
+	pr_cont("read-exits: %ld\n", data_race(n_read_exits));
 
 	pr_alert("%s%s ", torture_type, TORTURE_FLAG);
 	if (atomic_read(&n_rcu_torture_mberror) ||
@@ -1634,7 +1641,8 @@ rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, const char *tag)
 		 "stall_cpu=%d stall_cpu_holdoff=%d stall_cpu_irqsoff=%d "
 		 "stall_cpu_block=%d "
 		 "n_barrier_cbs=%d "
-		 "onoff_interval=%d onoff_holdoff=%d\n",
+		 "onoff_interval=%d onoff_holdoff=%d "
+		 "read_exit_delay=%d read_exit_burst=%d\n",
 		 torture_type, tag, nrealreaders, nfakewriters,
 		 stat_interval, verbose, test_no_idle_hz, shuffle_interval,
 		 stutter, irqreader, fqs_duration, fqs_holdoff, fqs_stutter,
@@ -1643,7 +1651,8 @@ rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, const char *tag)
 		 stall_cpu, stall_cpu_holdoff, stall_cpu_irqsoff,
 		 stall_cpu_block,
 		 n_barrier_cbs,
-		 onoff_interval, onoff_holdoff);
+		 onoff_interval, onoff_holdoff,
+		 read_exit_delay, read_exit_burst);
 }
 
 static int rcutorture_booster_cleanup(unsigned int cpu)
@@ -2338,6 +2347,99 @@ static bool rcu_torture_can_boost(void)
 	return true;
 }
 
+static bool read_exit_child_stop;
+static bool read_exit_child_stopped;
+static wait_queue_head_t read_exit_wq;
+
+// Child kthread which just does an rcutorture reader and exits.
+static int rcu_torture_read_exit_child(void *trsp_in)
+{
+	struct torture_random_state *trsp = trsp_in;
+
+	set_user_nice(current, MAX_NICE);
+	// Minimize time between reading and exiting.
+	while (!kthread_should_stop())
+		schedule_timeout_uninterruptible(1);
+	(void)rcu_torture_one_read(trsp);
+	return 0;
+}
+
+// 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;
+	DEFINE_TORTURE_RANDOM(trs);
+
+	// Allocate and initialize.
+	set_user_nice(current, MAX_NICE);
+	VERBOSE_TOROUT_STRING("rcu_torture_read_exit: Start of test");
+
+	// 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;
+			}
+			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)) {
+			VERBOSE_TOROUT_ERRSTRING("out of memory");
+			errexit = true;
+			tsp = NULL;
+			break;
+		}
+		cond_resched();
+		kthread_stop(tsp);
+		n_read_exits ++;
+		stutter_wait("rcu_torture_read_exit");
+	} while (!errexit && !READ_ONCE(read_exit_child_stop));
+
+	// Clean up and exit.
+	smp_store_release(&read_exit_child_stopped, true); // After reaping.
+	smp_mb(); // Store before wakeup.
+	wake_up(&read_exit_wq);
+	while (!torture_must_stop())
+		schedule_timeout_uninterruptible(1);
+	torture_kthread_stopping("rcu_torture_read_exit");
+	return 0;
+}
+
+static int rcu_torture_read_exit_init(void)
+{
+	if (read_exit_burst <= 0)
+		return -EINVAL;
+	init_waitqueue_head(&read_exit_wq);
+	read_exit_child_stop = false;
+	read_exit_child_stopped = false;
+	return torture_create_kthread(rcu_torture_read_exit, NULL,
+				      read_exit_task);
+}
+
+static void rcu_torture_read_exit_cleanup(void)
+{
+	if (!read_exit_task)
+		return;
+	WRITE_ONCE(read_exit_child_stop, true);
+	smp_mb(); // Above write before wait.
+	wait_event(read_exit_wq, smp_load_acquire(&read_exit_child_stopped));
+	torture_stop_kthread(rcutorture_read_exit, read_exit_task);
+}
+
 static enum cpuhp_state rcutor_hp;
 
 static void
@@ -2359,6 +2461,7 @@ rcu_torture_cleanup(void)
 	}
 
 	show_rcu_gp_kthreads();
+	rcu_torture_read_exit_cleanup();
 	rcu_torture_barrier_cleanup();
 	torture_stop_kthread(rcu_torture_fwd_prog, fwd_prog_task);
 	torture_stop_kthread(rcu_torture_stall, stall_task);
@@ -2682,6 +2785,9 @@ rcu_torture_init(void)
 	firsterr = rcu_torture_barrier_init();
 	if (firsterr)
 		goto unwind;
+	firsterr = rcu_torture_read_exit_init();
+	if (firsterr)
+		goto unwind;
 	if (object_debug)
 		rcu_test_debug_objects();
 	torture_init_end();
-- 
2.9.5

[PATCH tip/core/rcu 05/23] torture: Set configfile variable to current scenario

[paulmck]

From: "Paul E. McKenney" <paulmck@kernel.org>

The torture-test recheck logic fails to set the configfile variable to
the current scenario, so this commit properly initializes this variable.
This change isn't critical given that all errors for a given scenario
follow that scenario's heading, but it is easier on the eyes to repeat it.
And this repetition also prevents confusion as to whether a given message
goes with the previous heading or the next one.

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

diff --git a/tools/testing/selftests/rcutorture/bin/kvm-recheck.sh b/tools/testing/selftests/rcutorture/bin/kvm-recheck.sh
index 736f047..2261aa6 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm-recheck.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm-recheck.sh
@@ -31,6 +31,7 @@ do
 			head -1 $resdir/log
 		fi
 		TORTURE_SUITE="`cat $i/../TORTURE_SUITE`"
+		configfile=`echo $i | sed -e 's,^.*/,,'`
 		rm -f $i/console.log.*.diags
 		kvm-recheck-${TORTURE_SUITE}.sh $i
 		if test -f "$i/qemu-retval" && test "`cat $i/qemu-retval`" -ne 0 && test "`cat $i/qemu-retval`" -ne 137
-- 
2.9.5

[PATCH tip/core/rcu 06/23] rcutorture: Handle non-statistic bang-string error messages

[paulmck]

From: "Paul E. McKenney" <paulmck@kernel.org>

The current console parsing assumes that console lines containing "!!!"
are statistics lines from which it can parse the number of rcutorture
too-short grace-period failures.  This prints confusing output for
other problems, including memory exhaustion.  This commit therefore
differentiates between these cases and prints an appropriate error string.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 .../testing/selftests/rcutorture/bin/parse-console.sh  | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/rcutorture/bin/parse-console.sh b/tools/testing/selftests/rcutorture/bin/parse-console.sh
index 4bf62d7..1c64ca8 100755
--- a/tools/testing/selftests/rcutorture/bin/parse-console.sh
+++ b/tools/testing/selftests/rcutorture/bin/parse-console.sh
@@ -44,11 +44,23 @@ then
 		tail -1 |
 		awk '
 		{
-			for (i=NF-8;i<=NF;i++)
+			normalexit = 1;
+			for (i=NF-8;i<=NF;i++) {
+				if (i <= 0 || i !~ /^[0-9]*$/) {
+					bangstring = $0;
+					gsub(/^\[[^]]*] /, "", bangstring);
+					print bangstring;
+					normalexit = 0;
+					exit 0;
+				}
 				sum+=$i;
+			}
 		}
-		END { print sum }'`
-		print_bug $title FAILURE, $nerrs instances
+		END {
+			if (normalexit)
+				print sum " instances"
+		}'`
+		print_bug $title FAILURE, $nerrs
 		exit
 	fi
 
-- 
2.9.5

[PATCH tip/core/rcu 07/23] rcutorture: NULL rcu_torture_current earlier in cleanup code

[paulmck]

From: "Paul E. McKenney" <paulmck@kernel.org>

Currently, the rcu_torture_current variable remains non-NULL until after
all readers have stopped.  During this time, rcu_torture_stats_print()
will think that the test is still ongoing, which can result in confusing
dmesg output.  This commit therefore NULLs rcu_torture_current immediately
after the rcu_torture_writer() kthread has decided to stop, thus informing
rcu_torture_stats_print() much sooner.

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 2621a33..5911207 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1172,6 +1172,7 @@ rcu_torture_writer(void *arg)
 					WARN(1, "%s: rtort_pipe_count: %d\n", __func__, rcu_tortures[i].rtort_pipe_count);
 				}
 	} while (!torture_must_stop());
+	rcu_torture_current = NULL;  // Let stats task know that we are done.
 	/* Reset expediting back to unexpedited. */
 	if (expediting > 0)
 		expediting = -expediting;
@@ -2473,7 +2474,6 @@ rcu_torture_cleanup(void)
 					     reader_tasks[i]);
 		kfree(reader_tasks);
 	}
-	rcu_torture_current = NULL;
 
 	if (fakewriter_tasks) {
 		for (i = 0; i < nfakewriters; i++) {
-- 
2.9.5

[PATCH tip/core/rcu 08/23] torture: Remove whitespace from identify_qemu_vcpus output

[paulmck]

From: "Paul E. McKenney" <paulmck@kernel.org>

The identify_qemu_vcpus bash function can return numbers including
whitespace characters, which can be a bit annoying in some bash
dollar-sign substitutions.  This commit therefore strips all spaces and
tabs from the value that identify_qemu_vcpus outputs.

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

diff --git a/tools/testing/selftests/rcutorture/bin/functions.sh b/tools/testing/selftests/rcutorture/bin/functions.sh
index 436b154..51f3464 100644
--- a/tools/testing/selftests/rcutorture/bin/functions.sh
+++ b/tools/testing/selftests/rcutorture/bin/functions.sh
@@ -231,7 +231,7 @@ identify_qemu_args () {
 # Returns the number of virtual CPUs available to the aggregate of the
 # guest OSes.
 identify_qemu_vcpus () {
-	lscpu | grep '^CPU(s):' | sed -e 's/CPU(s)://'
+	lscpu | grep '^CPU(s):' | sed -e 's/CPU(s)://' -e 's/[ 	]*//g'
 }
 
 # print_bug
-- 
2.9.5

[PATCH tip/core/rcu 09/23] torture: Add --allcpus argument to the kvm.sh script

[paulmck]

From: "Paul E. McKenney" <paulmck@kernel.org>

Leaving off the kvm.sh script's --cpus argument results in the script
testing the scenarios sequentially, which can be quite slow.  However,
having to specify the actual number of CPUs can be error-prone.
This commit therefore adds a --allcpus argument that causes kvm.sh to
use all available CPUs.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 tools/testing/selftests/rcutorture/bin/kvm.sh | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/testing/selftests/rcutorture/bin/kvm.sh b/tools/testing/selftests/rcutorture/bin/kvm.sh
index c279cf9..7dbce7a 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm.sh
@@ -73,6 +73,10 @@ usage () {
 while test $# -gt 0
 do
 	case "$1" in
+	--allcpus)
+		cpus=$TORTURE_ALLOTED_CPUS
+		max_cpus=$TORTURE_ALLOTED_CPUS
+		;;
 	--bootargs|--bootarg)
 		checkarg --bootargs "(list of kernel boot arguments)" "$#" "$2" '.*' '^--'
 		TORTURE_BOOTARGS="$2"
-- 
2.9.5

[PATCH tip/core/rcu 10/23] rcu/rcutorture: Replace 0 with false

[paulmck]

From: Jules Irenge <jbi.octave@gmail.com>

Coccinelle reports a warning

WARNING: Assignment of 0/1 to bool variable

The root cause is that the variable lastphase is a bool, but is
initialised with integer 0.  This commit therefore replaces the 0 with
a false.

Signed-off-by: Jules Irenge <jbi.octave@gmail.com>
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 5911207..37455a1 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -2185,7 +2185,7 @@ static void rcu_torture_barrier1cb(void *rcu_void)
 static int rcu_torture_barrier_cbs(void *arg)
 {
 	long myid = (long)arg;
-	bool lastphase = 0;
+	bool lastphase = false;
 	bool newphase;
 	struct rcu_head rcu;
 
-- 
2.9.5

[PATCH tip/core/rcu 11/23] torture: Create qemu-cmd in --buildonly runs

[paulmck]

From: "Paul E. McKenney" <paulmck@kernel.org>

One reason to do a --buildonly run is to use the build products elsewhere,
for example, to do the actual test on some other system.  Part of doing
the test is the actual qemu command, which is not currently produced
by --buildonly runs.  This commit therefore causes --buildonly runs to
create this file.

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

diff --git a/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh b/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
index 1b9aebd..064dd73 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
@@ -153,6 +153,7 @@ qemu_append="`identify_qemu_append "$QEMU"`"
 boot_args="`configfrag_boot_params "$boot_args" "$config_template"`"
 # Generate kernel-version-specific boot parameters
 boot_args="`per_version_boot_params "$boot_args" $resdir/.config $seconds`"
+echo $QEMU $qemu_args -m $TORTURE_QEMU_MEM -kernel $KERNEL -append \"$qemu_append $boot_args\" > $resdir/qemu-cmd
 
 if test -n "$TORTURE_BUILDONLY"
 then
@@ -161,7 +162,6 @@ then
 	exit 0
 fi
 echo "NOTE: $QEMU either did not run or was interactive" > $resdir/console.log
-echo $QEMU $qemu_args -m $TORTURE_QEMU_MEM -kernel $KERNEL -append \"$qemu_append $boot_args\" > $resdir/qemu-cmd
 ( $QEMU $qemu_args -m $TORTURE_QEMU_MEM -kernel $KERNEL -append "$qemu_append $boot_args" > $resdir/qemu-output 2>&1 & echo $! > $resdir/qemu_pid; wait `cat  $resdir/qemu_pid`; echo $? > $resdir/qemu-retval ) &
 commandcompleted=0
 sleep 10 # Give qemu's pid a chance to reach the file
-- 
2.9.5

[PATCH tip/core/rcu 12/23] torture: Add a stop-run capability

[paulmck]

From: "Paul E. McKenney" <paulmck@kernel.org>

When bisecting RCU issues, it is often the case that the first error in
an unsuccessful run will happen quickly, but that a successful run must
go on for some time in order to obtain a sufficiently low false-negative
error rate.  In many cases, a bisection requires multiple concurrent
runs, in which case the first failure in any run indicates failure,
pure and simple.  In such cases, it would speed things up greatly if
the first failure terminated all runs.

This commit therefore adds scripting that checks for a file named "STOP"
in the top-level results directory, terminating the run when it appears.
Note that in-progress builds will continue until completion, but future
builds and all runs will be cut short.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 tools/testing/selftests/rcutorture/bin/jitter.sh         |  6 ++++++
 tools/testing/selftests/rcutorture/bin/kvm-build.sh      |  6 ++++++
 tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh | 13 +++++++++++--
 tools/testing/selftests/rcutorture/bin/kvm.sh            |  2 ++
 4 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/rcutorture/bin/jitter.sh b/tools/testing/selftests/rcutorture/bin/jitter.sh
index 30cb5b2..188b864 100755
--- a/tools/testing/selftests/rcutorture/bin/jitter.sh
+++ b/tools/testing/selftests/rcutorture/bin/jitter.sh
@@ -46,6 +46,12 @@ do
 		exit 0;
 	fi
 
+	# Check for stop request.
+	if test -f "$TORTURE_STOPFILE"
+	then
+		exit 1;
+	fi
+
 	# Set affinity to randomly selected online CPU
 	if cpus=`grep 1 /sys/devices/system/cpu/*/online 2>&1 |
 		 sed -e 's,/[^/]*$,,' -e 's/^[^0-9]*//'`
diff --git a/tools/testing/selftests/rcutorture/bin/kvm-build.sh b/tools/testing/selftests/rcutorture/bin/kvm-build.sh
index 18d6518..115e182 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm-build.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm-build.sh
@@ -9,6 +9,12 @@
 #
 # Authors: Paul E. McKenney <paulmck@linux.ibm.com>
 
+if test -f "$TORTURE_STOPFILE"
+then
+	echo "kvm-build.sh early exit due to run STOP request"
+	exit 1
+fi
+
 config_template=${1}
 if test -z "$config_template" -o ! -f "$config_template" -o ! -r "$config_template"
 then
diff --git a/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh b/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
index 064dd73..5ec095d 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
@@ -182,7 +182,7 @@ do
 	kruntime=`gawk 'BEGIN { print systime() - '"$kstarttime"' }' < /dev/null`
 	if test -z "$qemu_pid" || kill -0 "$qemu_pid" > /dev/null 2>&1
 	then
-		if test $kruntime -ge $seconds
+		if test $kruntime -ge $seconds -o -f "$TORTURE_STOPFILE"
 		then
 			break;
 		fi
@@ -211,10 +211,19 @@ then
 fi
 if test $commandcompleted -eq 0 -a -n "$qemu_pid"
 then
-	echo Grace period for qemu job at pid $qemu_pid
+	if ! test -f "$TORTURE_STOPFILE"
+	then
+		echo Grace period for qemu job at pid $qemu_pid
+	fi
 	oldline="`tail $resdir/console.log`"
 	while :
 	do
+		if test -f "$TORTURE_STOPFILE"
+		then
+			echo "PID $qemu_pid killed due to run STOP request" >> $resdir/Warnings 2>&1
+			kill -KILL $qemu_pid
+			break
+		fi
 		kruntime=`gawk 'BEGIN { print systime() - '"$kstarttime"' }' < /dev/null`
 		if kill -0 $qemu_pid > /dev/null 2>&1
 		then
diff --git a/tools/testing/selftests/rcutorture/bin/kvm.sh b/tools/testing/selftests/rcutorture/bin/kvm.sh
index 7dbce7a..3578c85 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm.sh
@@ -337,6 +337,8 @@ then
 	mkdir -p "$resdir" || :
 fi
 mkdir $resdir/$ds
+TORTURE_RESDIR="$resdir/$ds"; export TORTURE_RESDIR
+TORTURE_STOPFILE="$resdir/$ds/STOP"; export TORTURE_STOPFILE
 echo Results directory: $resdir/$ds
 echo $scriptname $args
 touch $resdir/$ds/log
-- 
2.9.5

[PATCH tip/core/rcu 13/23] torture: Abstract out console-log error detection

[paulmck]

From: "Paul E. McKenney" <paulmck@kernel.org>

This commit pulls the simple pattern-based error detection from the
console log into a new console-badness.sh file.  This will enable future
commits to end a run on the first error.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 .../testing/selftests/rcutorture/bin/console-badness.sh  | 16 ++++++++++++++++
 tools/testing/selftests/rcutorture/bin/parse-console.sh  |  5 +----
 2 files changed, 17 insertions(+), 4 deletions(-)
 create mode 100755 tools/testing/selftests/rcutorture/bin/console-badness.sh

diff --git a/tools/testing/selftests/rcutorture/bin/console-badness.sh b/tools/testing/selftests/rcutorture/bin/console-badness.sh
new file mode 100755
index 0000000..0e4c0b2
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/bin/console-badness.sh
@@ -0,0 +1,16 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0+
+#
+# Scan standard input for error messages, dumping any found to standard
+# output.
+#
+# Usage: console-badness.sh
+#
+# Copyright (C) 2020 Facebook, Inc.
+#
+# Authors: Paul E. McKenney <paulmck@kernel.org>
+
+egrep 'Badness|WARNING:|Warn|BUG|===========|Call Trace:|Oops:|detected stalls on CPUs/tasks:|self-detected stall on CPU|Stall ended before state dump start|\?\?\? Writer stall state|rcu_.*kthread starved for|!!!' |
+grep -v 'ODEBUG: ' |
+grep -v 'This means that this is a DEBUG kernel and it is' |
+grep -v 'Warning: unable to open an initial console'
diff --git a/tools/testing/selftests/rcutorture/bin/parse-console.sh b/tools/testing/selftests/rcutorture/bin/parse-console.sh
index 1c64ca8..98478e1 100755
--- a/tools/testing/selftests/rcutorture/bin/parse-console.sh
+++ b/tools/testing/selftests/rcutorture/bin/parse-console.sh
@@ -116,10 +116,7 @@ then
 	fi
 fi | tee -a $file.diags
 
-egrep 'Badness|WARNING:|Warn|BUG|===========|Call Trace:|Oops:|detected stalls on CPUs/tasks:|self-detected stall on CPU|Stall ended before state dump start|\?\?\? Writer stall state|rcu_.*kthread starved for' < $file |
-grep -v 'ODEBUG: ' |
-grep -v 'This means that this is a DEBUG kernel and it is' |
-grep -v 'Warning: unable to open an initial console' > $T.diags
+console-badness.sh < $file > $T.diags
 if test -s $T.diags
 then
 	print_warning "Assertion failure in $file $title"
-- 
2.9.5

[PATCH tip/core/rcu 14/23] rcutorture: Check for unwatched readers

[paulmck]

From: "Paul E. McKenney" <paulmck@kernel.org>

RCU is supposed to be watching all non-idle kernel code and also all
softirq handlers.  This commit adds some teeth to this statement by
adding a WARN_ON_ONCE().

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 37455a1..9c31001 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1377,6 +1377,7 @@ static bool rcu_torture_one_read(struct torture_random_state *trsp)
 	struct rt_read_seg *rtrsp1;
 	unsigned long long ts;
 
+	WARN_ON_ONCE(!rcu_is_watching());
 	newstate = rcutorture_extend_mask(readstate, trsp);
 	rcutorture_one_extend(&readstate, newstate, trsp, rtrsp++);
 	started = cur_ops->get_gp_seq();
-- 
2.9.5

[PATCH tip/core/rcu 15/23] torture: Pass --kmake-arg to all make invocations

[paulmck]

From: Marco Elver <elver@google.com>

We need to pass the arguments provided to --kmake-arg to all make
invocations. In particular, the make invocations generating the configs
need to see the final make arguments, e.g. if config variables depend on
particular variables that are passed to make.

For example, when using '--kcsan --kmake-arg CC=clang-11', we would lose
CONFIG_KCSAN=y due to 'make oldconfig' not seeing that we want to use a
compiler that supports KCSAN.

Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 tools/testing/selftests/rcutorture/bin/configinit.sh | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/rcutorture/bin/configinit.sh b/tools/testing/selftests/rcutorture/bin/configinit.sh
index 93e80a4..d6e5ce0 100755
--- a/tools/testing/selftests/rcutorture/bin/configinit.sh
+++ b/tools/testing/selftests/rcutorture/bin/configinit.sh
@@ -32,11 +32,11 @@ if test -z "$TORTURE_TRUST_MAKE"
 then
 	make clean > $resdir/Make.clean 2>&1
 fi
-make $TORTURE_DEFCONFIG > $resdir/Make.defconfig.out 2>&1
+make $TORTURE_KMAKE_ARG $TORTURE_DEFCONFIG > $resdir/Make.defconfig.out 2>&1
 mv .config .config.sav
 sh $T/upd.sh < .config.sav > .config
 cp .config .config.new
-yes '' | make oldconfig > $resdir/Make.oldconfig.out 2> $resdir/Make.oldconfig.err
+yes '' | make $TORTURE_KMAKE_ARG oldconfig > $resdir/Make.oldconfig.out 2> $resdir/Make.oldconfig.err
 
 # verify new config matches specification.
 configcheck.sh .config $c
-- 
2.9.5

[PATCH tip/core/rcu 16/23] torture: Correctly summarize build-only runs

[paulmck]

From: "Paul E. McKenney" <paulmck@kernel.org>

Currently, kvm-recheck.sh complains that qemu failed for --buildonly
runs, which is sort of true given that qemu can hardly succeed if not
invoked in the first place.  Nevertheless, this commit swaps the order
of checks in kvm-recheck.sh so that --buildonly runs will be summarized
more straightforwardly.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 tools/testing/selftests/rcutorture/bin/kvm-recheck.sh | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/rcutorture/bin/kvm-recheck.sh b/tools/testing/selftests/rcutorture/bin/kvm-recheck.sh
index 2261aa6..357899c 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm-recheck.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm-recheck.sh
@@ -56,15 +56,15 @@ do
 				cat $i/Warnings
 			fi
 		else
-			if test -f "$i/qemu-cmd"
-			then
-				print_bug qemu failed
-				echo "   $i"
-			elif test -f "$i/buildonly"
+			if test -f "$i/buildonly"
 			then
 				echo Build-only run, no boot/test
 				configcheck.sh $i/.config $i/ConfigFragment
 				parse-build.sh $i/Make.out $configfile
+			elif test -f "$i/qemu-cmd"
+			then
+				print_bug qemu failed
+				echo "   $i"
 			else
 				print_bug Build failed
 				echo "   $i"
-- 
2.9.5

[PATCH tip/core/rcu 17/23] torture: Improve diagnostic for KCSAN-incapable compilers

[paulmck]

From: "Paul E. McKenney" <paulmck@kernel.org>

Using --kcsan when the compiler does not support KCSAN results in this:

:CONFIG_KCSAN=y: improperly set
:CONFIG_KCSAN_REPORT_ONCE_IN_MS=100000: improperly set
:CONFIG_KCSAN_VERBOSE=y: improperly set
:CONFIG_KCSAN_INTERRUPT_WATCHER=y: improperly set
Clean KCSAN run in /home/git/linux-rcu/tools/testing/selftests/rcutorture/res/2020.06.16-09.53.16

This is a bit obtuse, so this commit adds checks resulting in this:

:CONFIG_KCSAN=y: improperly set
:CONFIG_KCSAN_REPORT_ONCE_IN_MS=100000: improperly set
:CONFIG_KCSAN_VERBOSE=y: improperly set
:CONFIG_KCSAN_INTERRUPT_WATCHER=y: improperly set
Compiler or architecture does not support KCSAN!
Did you forget to switch your compiler with --kmake-arg CC=<cc-that-supports-kcsan>?

Suggested-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Marco Elver <elver@google.com>
---
 tools/testing/selftests/rcutorture/bin/kvm-recheck.sh | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/rcutorture/bin/kvm-recheck.sh b/tools/testing/selftests/rcutorture/bin/kvm-recheck.sh
index 357899c..840a467 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm-recheck.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm-recheck.sh
@@ -44,7 +44,8 @@ do
 			then
 				echo QEMU killed
 			fi
-			configcheck.sh $i/.config $i/ConfigFragment
+			configcheck.sh $i/.config $i/ConfigFragment > $T 2>&1
+			cat $T
 			if test -r $i/Make.oldconfig.err
 			then
 				cat $i/Make.oldconfig.err
@@ -73,7 +74,11 @@ do
 	done
 	if test -f "$rd/kcsan.sum"
 	then
-		if test -s "$rd/kcsan.sum"
+		if grep -q CONFIG_KCSAN=y $T
+		then
+			echo "Compiler or architecture does not support KCSAN!"
+			echo Did you forget to switch your compiler with '--kmake-arg CC=<cc-that-supports-kcsan>'?
+		elif test -s "$rd/kcsan.sum"
 		then
 			echo KCSAN summary in $rd/kcsan.sum
 		else
-- 
2.9.5

[PATCH tip/core/rcu 18/23] torture: Add more tracing crib notes to kvm.sh

[paulmck]

From: "Paul E. McKenney" <paulmck@kernel.org>

This commit adds a few more hints about how to use tracing as comments
at the end of kvm.sh.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 tools/testing/selftests/rcutorture/bin/kvm.sh | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/testing/selftests/rcutorture/bin/kvm.sh b/tools/testing/selftests/rcutorture/bin/kvm.sh
index 3578c85..bdfa0c0 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm.sh
@@ -503,3 +503,7 @@ fi
 # Tracing: trace_event=rcu:rcu_grace_period,rcu:rcu_future_grace_period,rcu:rcu_grace_period_init,rcu:rcu_nocb_wake,rcu:rcu_preempt_task,rcu:rcu_unlock_preempted_task,rcu:rcu_quiescent_state_report,rcu:rcu_fqs,rcu:rcu_callback,rcu:rcu_kfree_callback,rcu:rcu_batch_start,rcu:rcu_invoke_callback,rcu:rcu_invoke_kfree_callback,rcu:rcu_batch_end,rcu:rcu_torture_read,rcu:rcu_barrier
 # Function-graph tracing: ftrace=function_graph ftrace_graph_filter=sched_setaffinity,migration_cpu_stop
 # Also --kconfig "CONFIG_FUNCTION_TRACER=y CONFIG_FUNCTION_GRAPH_TRACER=y"
+# Control buffer size: --bootargs trace_buf_size=3k
+# Get trace-buffer dumps on all oopses: --bootargs ftrace_dump_on_oops
+# Ditto, but dump only the oopsing CPU: --bootargs ftrace_dump_on_oops=orig_cpu
+# Heavy-handed way to also dump on warnings: --bootargs panic_on_warn
-- 
2.9.5

[PATCH tip/core/rcu 19/23] torture: Add kvm-tranform.sh script for qemu-cmd files

[paulmck]

From: "Paul E. McKenney" <paulmck@kernel.org>

This commit adds a script that transforms qemu-cmd files to allow them
and the corresponding kernels to be run in contexts other than the one
that they were created for, including on systems other than the one that
they were built on.  For example, this allows the build products from a
--buildonly run to be transformed to allow distributed rcutorture testing.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 .../selftests/rcutorture/bin/kvm-transform.sh      | 51 ++++++++++++++++++++++
 1 file changed, 51 insertions(+)
 create mode 100755 tools/testing/selftests/rcutorture/bin/kvm-transform.sh

diff --git a/tools/testing/selftests/rcutorture/bin/kvm-transform.sh b/tools/testing/selftests/rcutorture/bin/kvm-transform.sh
new file mode 100755
index 0000000..c45a953
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/bin/kvm-transform.sh
@@ -0,0 +1,51 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0+
+#
+# Transform a qemu-cmd file to allow reuse.
+#
+# Usage: kvm-transform.sh bzImage console.log < qemu-cmd-in > qemu-cmd-out
+#
+#	bzImage: Kernel and initrd from the same prior kvm.sh run.
+#	console.log: File into which to place console output.
+#
+# The original qemu-cmd file is provided on standard input.
+# The transformed qemu-cmd file is on standard output.
+# The transformation assumes that the qemu command is confined to a
+# single line.  It also assumes no whitespace in filenames.
+#
+# Copyright (C) 2020 Facebook, Inc.
+#
+# Authors: Paul E. McKenney <paulmck@kernel.org>
+
+image="$1"
+if test -z "$image"
+then
+	echo Need kernel image file.
+	exit 1
+fi
+consolelog="$2"
+if test -z "$consolelog"
+then
+	echo "Need console log file name."
+	exit 1
+fi
+
+awk -v image="$image" -v consolelog="$consolelog" '
+{
+	line = "";
+	for (i = 1; i <= NF; i++) {
+		if (line == "")
+			line = $i;
+		else
+			line = line " " $i;
+		if ($i == "-serial") {
+			i++;
+			line = line " file:" consolelog;
+		}
+		if ($i == "-kernel") {
+			i++;
+			line = line " " image;
+		}
+	}
+	print line;
+}'
-- 
2.9.5

[PATCH tip/core/rcu 20/23] torture: Dump ftrace at shutdown only if requested

[paulmck]

From: "Paul E. McKenney" <paulmck@kernel.org>

If there is a large number of torture tests running concurrently,
all of which are dumping large ftrace buffers at shutdown time, the
resulting dumping can take a very long time, particularly on systems
with rotating-rust storage.  This commit therefore adds a default-off
torture.ftrace_dump_at_shutdown module parameter that enables
shutdown-time ftrace-buffer dumping.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 Documentation/admin-guide/kernel-parameters.txt | 7 +++++++
 kernel/torture.c                                | 6 +++++-
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index a0dcc92..9f11ff8 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -5096,6 +5096,13 @@
 			Prevent the CPU-hotplug component of torturing
 			until after init has spawned.
 
+	torture.ftrace_dump_at_shutdown= [KNL]
+			Dump the ftrace buffer at torture-test shutdown,
+			even if there were no errors.  This can be a
+			very costly operation when many torture tests
+			are running concurrently, especially on systems
+			with rotating-rust storage.
+
 	tp720=		[HW,PS2]
 
 	tpm_suspend_pcr=[HW,TPM]
diff --git a/kernel/torture.c b/kernel/torture.c
index a1a4148..1061492 100644
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -45,6 +45,9 @@ MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.ibm.com>");
 static bool disable_onoff_at_boot;
 module_param(disable_onoff_at_boot, bool, 0444);
 
+static bool ftrace_dump_at_shutdown;
+module_param(ftrace_dump_at_shutdown, bool, 0444);
+
 static char *torture_type;
 static int verbose;
 
@@ -527,7 +530,8 @@ static int torture_shutdown(void *arg)
 		torture_shutdown_hook();
 	else
 		VERBOSE_TOROUT_STRING("No torture_shutdown_hook(), skipping.");
-	rcu_ftrace_dump(DUMP_ALL);
+	if (ftrace_dump_at_shutdown)
+		rcu_ftrace_dump(DUMP_ALL);
 	kernel_power_off();	/* Shut down the system. */
 	return 0;
 }
-- 
2.9.5

[PATCH tip/core/rcu 21/23] torture: Avoid duplicate specification of qemu command

[paulmck]

From: "Paul E. McKenney" <paulmck@kernel.org>

Currently, the qemu command is constructed twice, once to dump it
to the qemu-cmd file and again to execute it.  This is of course an
accident waiting to happen, but is done to ensure that the remainder
of the script has an accurate idea of the running qemu command's PID.
This commit therefore places both the qemu command and the PID capture
into a new temporary file and sources that temporary file.  Thus the
single construction of the qemu command into the qemu-cmd file suffices
for both purposes.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh b/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
index 5ec095d..484445b 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
@@ -161,8 +161,16 @@ then
 	touch $resdir/buildonly
 	exit 0
 fi
+
+# Decorate qemu-cmd with redirection, backgrounding, and PID capture
+sed -e 's/$/ 2>\&1 \&/' < $resdir/qemu-cmd > $T/qemu-cmd
+echo 'echo $! > $resdir/qemu_pid' >> $T/qemu-cmd
+
+# In case qemu refuses to run...
 echo "NOTE: $QEMU either did not run or was interactive" > $resdir/console.log
-( $QEMU $qemu_args -m $TORTURE_QEMU_MEM -kernel $KERNEL -append "$qemu_append $boot_args" > $resdir/qemu-output 2>&1 & echo $! > $resdir/qemu_pid; wait `cat  $resdir/qemu_pid`; echo $? > $resdir/qemu-retval ) &
+
+# Attempt to run qemu
+( . $T/qemu-cmd; wait `cat  $resdir/qemu_pid`; echo $? > $resdir/qemu-retval ) &
 commandcompleted=0
 sleep 10 # Give qemu's pid a chance to reach the file
 if test -s "$resdir/qemu_pid"
-- 
2.9.5

[PATCH tip/core/rcu 22/23] torture: Remove obsolete "cd $KVM"

[paulmck]

From: "Paul E. McKenney" <paulmck@kernel.org>

In the dim distant past, qemu commands needed to be run from the
rcutorture directory, but this is no longer the case.  This commit
therefore removes the now-useless "cd $KVM" from the kvm-test-1-run.sh
script.

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

diff --git a/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh b/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
index 484445b..e07779a 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
@@ -124,7 +124,6 @@ seconds=$4
 qemu_args=$5
 boot_args=$6
 
-cd $KVM
 kstarttime=`gawk 'BEGIN { print systime() }' < /dev/null`
 if test -z "$TORTURE_BUILDONLY"
 then
-- 
2.9.5

[PATCH tip/core/rcu 23/23] rcutorture: Remove KCSAN stubs

[paulmck]

From: "Paul E. McKenney" <paulmck@kernel.org>

KCSAN is now in mainline, so this commit removes the stubs for the
data_race(), ASSERT_EXCLUSIVE_WRITER(), and ASSERT_EXCLUSIVE_ACCESS()
macros.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/rcutorture.c | 13 -------------
 1 file changed, 13 deletions(-)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 9c31001..f78c646 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -52,19 +52,6 @@
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.ibm.com> and Josh Triplett <josh@joshtriplett.org>");
 
-#ifndef data_race
-#define data_race(expr)							\
-	({								\
-		expr;							\
-	})
-#endif
-#ifndef ASSERT_EXCLUSIVE_WRITER
-#define ASSERT_EXCLUSIVE_WRITER(var) do { } while (0)
-#endif
-#ifndef ASSERT_EXCLUSIVE_ACCESS
-#define ASSERT_EXCLUSIVE_ACCESS(var) do { } while (0)
-#endif
-
 /* Bits for ->extendables field, extendables param, and related definitions. */
 #define RCUTORTURE_RDR_SHIFT	 8	/* Put SRCU index in upper bits. */
 #define RCUTORTURE_RDR_MASK	 ((1 << RCUTORTURE_RDR_SHIFT) - 1)
-- 
2.9.5

[PATCH tip/core/rcu 01/10] fork: Annotate a data race in vm_area_dup()

[paulmck]

From: Qian Cai <cai@lca.pw>

struct vm_area_struct could be accessed concurrently as noticed by
KCSAN,

 write to 0xffff9cf8bba08ad8 of 8 bytes by task 14263 on cpu 35:
  vma_interval_tree_insert+0x101/0x150:
  rb_insert_augmented_cached at include/linux/rbtree_augmented.h:58
  (inlined by) vma_interval_tree_insert at mm/interval_tree.c:23
  __vma_link_file+0x6e/0xe0
  __vma_link_file at mm/mmap.c:629
  vma_link+0xa2/0x120
  mmap_region+0x753/0xb90
  do_mmap+0x45c/0x710
  vm_mmap_pgoff+0xc0/0x130
  ksys_mmap_pgoff+0x1d1/0x300
  __x64_sys_mmap+0x33/0x40
  do_syscall_64+0x91/0xc44
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

 read to 0xffff9cf8bba08a80 of 200 bytes by task 14262 on cpu 122:
  vm_area_dup+0x6a/0xe0
  vm_area_dup at kernel/fork.c:362
  __split_vma+0x72/0x2a0
  __split_vma at mm/mmap.c:2661
  split_vma+0x5a/0x80
  mprotect_fixup+0x368/0x3f0
  do_mprotect_pkey+0x263/0x420
  __x64_sys_mprotect+0x51/0x70
  do_syscall_64+0x91/0xc44
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

vm_area_dup() blindly copies all fields of original VMA to the new one.
This includes coping vm_area_struct::shared.rb which is normally
protected by i_mmap_lock. But this is fine because the read value will
be overwritten on the following __vma_link_file() under proper
protection. Thus, mark it as an intentional data race and insert a few
assertions for the fields that should not be modified concurrently.

Signed-off-by: Qian Cai <cai@lca.pw>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/fork.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index 142b236..bba10fb 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -359,7 +359,13 @@ struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
 	struct vm_area_struct *new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 
 	if (new) {
-		*new = *orig;
+		ASSERT_EXCLUSIVE_WRITER(orig->vm_flags);
+		ASSERT_EXCLUSIVE_WRITER(orig->vm_file);
+		/*
+		 * orig->shared.rb may be modified concurrently, but the clone
+		 * will be reinitialized.
+		 */
+		*new = data_race(*orig);
 		INIT_LIST_HEAD(&new->anon_vma_chain);
 		new->vm_next = new->vm_prev = NULL;
 	}
-- 
2.9.5

[PATCH tip/core/rcu 02/10] x86/mm/pat: Mark an intentional data race

[paulmck]

From: Qian Cai <cai@lca.pw>

cpa_4k_install could be accessed concurrently as noticed by KCSAN,

read to 0xffffffffaa59a000 of 8 bytes by interrupt on cpu 7:
cpa_inc_4k_install arch/x86/mm/pat/set_memory.c:131 [inline]
__change_page_attr+0x10cf/0x1840 arch/x86/mm/pat/set_memory.c:1514
__change_page_attr_set_clr+0xce/0x490 arch/x86/mm/pat/set_memory.c:1636
__set_pages_np+0xc4/0xf0 arch/x86/mm/pat/set_memory.c:2148
__kernel_map_pages+0xb0/0xc8 arch/x86/mm/pat/set_memory.c:2178
kernel_map_pages include/linux/mm.h:2719 [inline] <snip>

write to 0xffffffffaa59a000 of 8 bytes by task 1 on cpu 6:
cpa_inc_4k_install arch/x86/mm/pat/set_memory.c:131 [inline]
__change_page_attr+0x10ea/0x1840 arch/x86/mm/pat/set_memory.c:1514
__change_page_attr_set_clr+0xce/0x490 arch/x86/mm/pat/set_memory.c:1636
__set_pages_p+0xc4/0xf0 arch/x86/mm/pat/set_memory.c:2129
__kernel_map_pages+0x2e/0xc8 arch/x86/mm/pat/set_memory.c:2176
kernel_map_pages include/linux/mm.h:2719 [inline] <snip>

Both accesses are due to the same "cpa_4k_install++" in
cpa_inc_4k_install. A data race here could be potentially undesirable:
depending on compiler optimizations or how x86 executes a non-LOCK'd
increment, it may lose increments, corrupt the counter, etc. Since this
counter only seems to be used for printing some stats, this data race
itself is unlikely to cause harm to the system though. Thus, mark this
intentional data race using the data_race() marco.

Suggested-by: Macro Elver <elver@google.com>
Signed-off-by: Qian Cai <cai@lca.pw>
Acked-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 arch/x86/mm/pat/set_memory.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index 77e0430..d1b2a88 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -135,7 +135,7 @@ static inline void cpa_inc_2m_checked(void)
 
 static inline void cpa_inc_4k_install(void)
 {
-	cpa_4k_install++;
+	data_race(cpa_4k_install++);
 }
 
 static inline void cpa_inc_lp_sameprot(int level)
-- 
2.9.5

[PATCH tip/core/rcu 03/10] rculist: Add ASSERT_EXCLUSIVE_ACCESS() to __list_splice_init_rcu()

[paulmck]

From: "Paul E. McKenney" <paulmck@kernel.org>

After the sync() in __list_splice_init_rcu(), there should be no
readers traversing the old list.  This commit therefore enlists the
help of KCSAN to verify this condition via a pair of calls to
ASSERT_EXCLUSIVE_ACCESS().

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Marco Elver <elver@google.com>
---
 include/linux/rculist.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/linux/rculist.h b/include/linux/rculist.h
index df587d1..2ebd112 100644
--- a/include/linux/rculist.h
+++ b/include/linux/rculist.h
@@ -248,6 +248,8 @@ static inline void __list_splice_init_rcu(struct list_head *list,
 	 */
 
 	sync();
+	ASSERT_EXCLUSIVE_ACCESS(*first);
+	ASSERT_EXCLUSIVE_ACCESS(*last);
 
 	/*
 	 * Readers are finished with the source list, so perform splice.
-- 
2.9.5

[PATCH tip/core/rcu 04/10] kcsan: Add test suite

[paulmck]

From: Marco Elver <elver@google.com>

This adds KCSAN test focusing on behaviour of the integrated runtime.
Tests various race scenarios, and verifies the reports generated to
console. Makes use of KUnit for test organization, and the Torture
framework for test thread control.

Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/kcsan/Makefile     |    3 +
 kernel/kcsan/kcsan-test.c | 1084 +++++++++++++++++++++++++++++++++++++++++++++
 lib/Kconfig.kcsan         |   23 +-
 3 files changed, 1109 insertions(+), 1 deletion(-)
 create mode 100644 kernel/kcsan/kcsan-test.c

diff --git a/kernel/kcsan/Makefile b/kernel/kcsan/Makefile
index d4999b3..14533cf 100644
--- a/kernel/kcsan/Makefile
+++ b/kernel/kcsan/Makefile
@@ -12,3 +12,6 @@ CFLAGS_core.o := $(call cc-option,-fno-conserve-stack,) \
 
 obj-y := core.o debugfs.o report.o
 obj-$(CONFIG_KCSAN_SELFTEST) += test.o
+
+CFLAGS_kcsan-test.o := $(CFLAGS_KCSAN) -g -fno-omit-frame-pointer
+obj-$(CONFIG_KCSAN_TEST) += kcsan-test.o
diff --git a/kernel/kcsan/kcsan-test.c b/kernel/kcsan/kcsan-test.c
new file mode 100644
index 0000000..a8c1150
--- /dev/null
+++ b/kernel/kcsan/kcsan-test.c
@@ -0,0 +1,1084 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KCSAN test with various race scenarious to test runtime behaviour. Since the
+ * interface with which KCSAN's reports are obtained is via the console, this is
+ * the output we should verify. For each test case checks the presence (or
+ * absence) of generated reports. Relies on 'console' tracepoint to capture
+ * reports as they appear in the kernel log.
+ *
+ * Makes use of KUnit for test organization, and the Torture framework for test
+ * thread control.
+ *
+ * Copyright (C) 2020, Google LLC.
+ * Author: Marco Elver <elver@google.com>
+ */
+
+#include <kunit/test.h>
+#include <linux/jiffies.h>
+#include <linux/kcsan-checks.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/seqlock.h>
+#include <linux/spinlock.h>
+#include <linux/string.h>
+#include <linux/timer.h>
+#include <linux/torture.h>
+#include <linux/tracepoint.h>
+#include <linux/types.h>
+#include <trace/events/printk.h>
+
+/* Points to current test-case memory access "kernels". */
+static void (*access_kernels[2])(void);
+
+static struct task_struct **threads; /* Lists of threads. */
+static unsigned long end_time;       /* End time of test. */
+
+/* Report as observed from console. */
+static struct {
+	spinlock_t lock;
+	int nlines;
+	char lines[3][512];
+} observed = {
+	.lock = __SPIN_LOCK_UNLOCKED(observed.lock),
+};
+
+/* Setup test checking loop. */
+static __no_kcsan_or_inline void
+begin_test_checks(void (*func1)(void), void (*func2)(void))
+{
+	kcsan_disable_current();
+
+	/*
+	 * Require at least as long as KCSAN_REPORT_ONCE_IN_MS, to ensure at
+	 * least one race is reported.
+	 */
+	end_time = jiffies + msecs_to_jiffies(CONFIG_KCSAN_REPORT_ONCE_IN_MS + 500);
+
+	/* Signal start; release potential initialization of shared data. */
+	smp_store_release(&access_kernels[0], func1);
+	smp_store_release(&access_kernels[1], func2);
+}
+
+/* End test checking loop. */
+static __no_kcsan_or_inline bool
+end_test_checks(bool stop)
+{
+	if (!stop && time_before(jiffies, end_time)) {
+		/* Continue checking */
+		might_sleep();
+		return false;
+	}
+
+	kcsan_enable_current();
+	return true;
+}
+
+/*
+ * Probe for console output: checks if a race was reported, and obtains observed
+ * lines of interest.
+ */
+__no_kcsan
+static void probe_console(void *ignore, const char *buf, size_t len)
+{
+	unsigned long flags;
+	int nlines;
+
+	/*
+	 * Note that KCSAN reports under a global lock, so we do not risk the
+	 * possibility of having multiple reports interleaved. If that were the
+	 * case, we'd expect tests to fail.
+	 */
+
+	spin_lock_irqsave(&observed.lock, flags);
+	nlines = observed.nlines;
+
+	if (strnstr(buf, "BUG: KCSAN: ", len) && strnstr(buf, "test_", len)) {
+		/*
+		 * KCSAN report and related to the test.
+		 *
+		 * The provided @buf is not NUL-terminated; copy no more than
+		 * @len bytes and let strscpy() add the missing NUL-terminator.
+		 */
+		strscpy(observed.lines[0], buf, min(len + 1, sizeof(observed.lines[0])));
+		nlines = 1;
+	} else if ((nlines == 1 || nlines == 2) && strnstr(buf, "bytes by", len)) {
+		strscpy(observed.lines[nlines++], buf, min(len + 1, sizeof(observed.lines[0])));
+
+		if (strnstr(buf, "race at unknown origin", len)) {
+			if (WARN_ON(nlines != 2))
+				goto out;
+
+			/* No second line of interest. */
+			strcpy(observed.lines[nlines++], "<none>");
+		}
+	}
+
+out:
+	WRITE_ONCE(observed.nlines, nlines); /* Publish new nlines. */
+	spin_unlock_irqrestore(&observed.lock, flags);
+}
+
+/* Check if a report related to the test exists. */
+__no_kcsan
+static bool report_available(void)
+{
+	return READ_ONCE(observed.nlines) == ARRAY_SIZE(observed.lines);
+}
+
+/* Report information we expect in a report. */
+struct expect_report {
+	/* Access information of both accesses. */
+	struct {
+		void *fn;    /* Function pointer to expected function of top frame. */
+		void *addr;  /* Address of access; unchecked if NULL. */
+		size_t size; /* Size of access; unchecked if @addr is NULL. */
+		int type;    /* Access type, see KCSAN_ACCESS definitions. */
+	} access[2];
+};
+
+/* Check observed report matches information in @r. */
+__no_kcsan
+static bool report_matches(const struct expect_report *r)
+{
+	const bool is_assert = (r->access[0].type | r->access[1].type) & KCSAN_ACCESS_ASSERT;
+	bool ret = false;
+	unsigned long flags;
+	typeof(observed.lines) expect;
+	const char *end;
+	char *cur;
+	int i;
+
+	/* Doubled-checked locking. */
+	if (!report_available())
+		return false;
+
+	/* Generate expected report contents. */
+
+	/* Title */
+	cur = expect[0];
+	end = &expect[0][sizeof(expect[0]) - 1];
+	cur += scnprintf(cur, end - cur, "BUG: KCSAN: %s in ",
+			 is_assert ? "assert: race" : "data-race");
+	if (r->access[1].fn) {
+		char tmp[2][64];
+		int cmp;
+
+		/* Expect lexographically sorted function names in title. */
+		scnprintf(tmp[0], sizeof(tmp[0]), "%pS", r->access[0].fn);
+		scnprintf(tmp[1], sizeof(tmp[1]), "%pS", r->access[1].fn);
+		cmp = strcmp(tmp[0], tmp[1]);
+		cur += scnprintf(cur, end - cur, "%ps / %ps",
+				 cmp < 0 ? r->access[0].fn : r->access[1].fn,
+				 cmp < 0 ? r->access[1].fn : r->access[0].fn);
+	} else {
+		scnprintf(cur, end - cur, "%pS", r->access[0].fn);
+		/* The exact offset won't match, remove it. */
+		cur = strchr(expect[0], '+');
+		if (cur)
+			*cur = '\0';
+	}
+
+	/* Access 1 */
+	cur = expect[1];
+	end = &expect[1][sizeof(expect[1]) - 1];
+	if (!r->access[1].fn)
+		cur += scnprintf(cur, end - cur, "race at unknown origin, with ");
+
+	/* Access 1 & 2 */
+	for (i = 0; i < 2; ++i) {
+		const char *const access_type =
+			(r->access[i].type & KCSAN_ACCESS_ASSERT) ?
+				((r->access[i].type & KCSAN_ACCESS_WRITE) ?
+					 "assert no accesses" :
+					 "assert no writes") :
+				((r->access[i].type & KCSAN_ACCESS_WRITE) ?
+					 "write" :
+					 "read");
+		const char *const access_type_aux =
+			(r->access[i].type & KCSAN_ACCESS_ATOMIC) ?
+				" (marked)" :
+				((r->access[i].type & KCSAN_ACCESS_SCOPED) ?
+					 " (scoped)" :
+					 "");
+
+		if (i == 1) {
+			/* Access 2 */
+			cur = expect[2];
+			end = &expect[2][sizeof(expect[2]) - 1];
+
+			if (!r->access[1].fn) {
+				/* Dummy string if no second access is available. */
+				strcpy(cur, "<none>");
+				break;
+			}
+		}
+
+		cur += scnprintf(cur, end - cur, "%s%s to ", access_type,
+				 access_type_aux);
+
+		if (r->access[i].addr) /* Address is optional. */
+			cur += scnprintf(cur, end - cur, "0x%px of %zu bytes",
+					 r->access[i].addr, r->access[i].size);
+	}
+
+	spin_lock_irqsave(&observed.lock, flags);
+	if (!report_available())
+		goto out; /* A new report is being captured. */
+
+	/* Finally match expected output to what we actually observed. */
+	ret = strstr(observed.lines[0], expect[0]) &&
+	      /* Access info may appear in any order. */
+	      ((strstr(observed.lines[1], expect[1]) &&
+		strstr(observed.lines[2], expect[2])) ||
+	       (strstr(observed.lines[1], expect[2]) &&
+		strstr(observed.lines[2], expect[1])));
+out:
+	spin_unlock_irqrestore(&observed.lock, flags);
+	return ret;
+}
+
+/* ===== Test kernels ===== */
+
+static long test_sink;
+static long test_var;
+/* @test_array should be large enough to fall into multiple watchpoint slots. */
+static long test_array[3 * PAGE_SIZE / sizeof(long)];
+static struct {
+	long val[8];
+} test_struct;
+static DEFINE_SEQLOCK(test_seqlock);
+
+/*
+ * Helper to avoid compiler optimizing out reads, and to generate source values
+ * for writes.
+ */
+__no_kcsan
+static noinline void sink_value(long v) { WRITE_ONCE(test_sink, v); }
+
+static noinline void test_kernel_read(void) { sink_value(test_var); }
+
+static noinline void test_kernel_write(void)
+{
+	test_var = READ_ONCE_NOCHECK(test_sink) + 1;
+}
+
+static noinline void test_kernel_write_nochange(void) { test_var = 42; }
+
+/* Suffixed by value-change exception filter. */
+static noinline void test_kernel_write_nochange_rcu(void) { test_var = 42; }
+
+static noinline void test_kernel_read_atomic(void)
+{
+	sink_value(READ_ONCE(test_var));
+}
+
+static noinline void test_kernel_write_atomic(void)
+{
+	WRITE_ONCE(test_var, READ_ONCE_NOCHECK(test_sink) + 1);
+}
+
+__no_kcsan
+static noinline void test_kernel_write_uninstrumented(void) { test_var++; }
+
+static noinline void test_kernel_data_race(void) { data_race(test_var++); }
+
+static noinline void test_kernel_assert_writer(void)
+{
+	ASSERT_EXCLUSIVE_WRITER(test_var);
+}
+
+static noinline void test_kernel_assert_access(void)
+{
+	ASSERT_EXCLUSIVE_ACCESS(test_var);
+}
+
+#define TEST_CHANGE_BITS 0xff00ff00
+
+static noinline void test_kernel_change_bits(void)
+{
+	if (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) {
+		/*
+		 * Avoid race of unknown origin for this test, just pretend they
+		 * are atomic.
+		 */
+		kcsan_nestable_atomic_begin();
+		test_var ^= TEST_CHANGE_BITS;
+		kcsan_nestable_atomic_end();
+	} else
+		WRITE_ONCE(test_var, READ_ONCE(test_var) ^ TEST_CHANGE_BITS);
+}
+
+static noinline void test_kernel_assert_bits_change(void)
+{
+	ASSERT_EXCLUSIVE_BITS(test_var, TEST_CHANGE_BITS);
+}
+
+static noinline void test_kernel_assert_bits_nochange(void)
+{
+	ASSERT_EXCLUSIVE_BITS(test_var, ~TEST_CHANGE_BITS);
+}
+
+/* To check that scoped assertions do trigger anywhere in scope. */
+static noinline void test_enter_scope(void)
+{
+	int x = 0;
+
+	/* Unrelated accesses to scoped assert. */
+	READ_ONCE(test_sink);
+	kcsan_check_read(&x, sizeof(x));
+}
+
+static noinline void test_kernel_assert_writer_scoped(void)
+{
+	ASSERT_EXCLUSIVE_WRITER_SCOPED(test_var);
+	test_enter_scope();
+}
+
+static noinline void test_kernel_assert_access_scoped(void)
+{
+	ASSERT_EXCLUSIVE_ACCESS_SCOPED(test_var);
+	test_enter_scope();
+}
+
+static noinline void test_kernel_rmw_array(void)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(test_array); ++i)
+		test_array[i]++;
+}
+
+static noinline void test_kernel_write_struct(void)
+{
+	kcsan_check_write(&test_struct, sizeof(test_struct));
+	kcsan_disable_current();
+	test_struct.val[3]++; /* induce value change */
+	kcsan_enable_current();
+}
+
+static noinline void test_kernel_write_struct_part(void)
+{
+	test_struct.val[3] = 42;
+}
+
+static noinline void test_kernel_read_struct_zero_size(void)
+{
+	kcsan_check_read(&test_struct.val[3], 0);
+}
+
+static noinline void test_kernel_seqlock_reader(void)
+{
+	unsigned int seq;
+
+	do {
+		seq = read_seqbegin(&test_seqlock);
+		sink_value(test_var);
+	} while (read_seqretry(&test_seqlock, seq));
+}
+
+static noinline void test_kernel_seqlock_writer(void)
+{
+	unsigned long flags;
+
+	write_seqlock_irqsave(&test_seqlock, flags);
+	test_var++;
+	write_sequnlock_irqrestore(&test_seqlock, flags);
+}
+
+/* ===== Test cases ===== */
+
+/* Simple test with normal data race. */
+__no_kcsan
+static void test_basic(struct kunit *test)
+{
+	const struct expect_report expect = {
+		.access = {
+			{ test_kernel_write, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
+			{ test_kernel_read, &test_var, sizeof(test_var), 0 },
+		},
+	};
+	static const struct expect_report never = {
+		.access = {
+			{ test_kernel_read, &test_var, sizeof(test_var), 0 },
+			{ test_kernel_read, &test_var, sizeof(test_var), 0 },
+		},
+	};
+	bool match_expect = false;
+	bool match_never = false;
+
+	begin_test_checks(test_kernel_write, test_kernel_read);
+	do {
+		match_expect |= report_matches(&expect);
+		match_never = report_matches(&never);
+	} while (!end_test_checks(match_never));
+	KUNIT_EXPECT_TRUE(test, match_expect);
+	KUNIT_EXPECT_FALSE(test, match_never);
+}
+
+/*
+ * Stress KCSAN with lots of concurrent races on different addresses until
+ * timeout.
+ */
+__no_kcsan
+static void test_concurrent_races(struct kunit *test)
+{
+	const struct expect_report expect = {
+		.access = {
+			/* NULL will match any address. */
+			{ test_kernel_rmw_array, NULL, 0, KCSAN_ACCESS_WRITE },
+			{ test_kernel_rmw_array, NULL, 0, 0 },
+		},
+	};
+	static const struct expect_report never = {
+		.access = {
+			{ test_kernel_rmw_array, NULL, 0, 0 },
+			{ test_kernel_rmw_array, NULL, 0, 0 },
+		},
+	};
+	bool match_expect = false;
+	bool match_never = false;
+
+	begin_test_checks(test_kernel_rmw_array, test_kernel_rmw_array);
+	do {
+		match_expect |= report_matches(&expect);
+		match_never |= report_matches(&never);
+	} while (!end_test_checks(false));
+	KUNIT_EXPECT_TRUE(test, match_expect); /* Sanity check matches exist. */
+	KUNIT_EXPECT_FALSE(test, match_never);
+}
+
+/* Test the KCSAN_REPORT_VALUE_CHANGE_ONLY option. */
+__no_kcsan
+static void test_novalue_change(struct kunit *test)
+{
+	const struct expect_report expect = {
+		.access = {
+			{ test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
+			{ test_kernel_read, &test_var, sizeof(test_var), 0 },
+		},
+	};
+	bool match_expect = false;
+
+	begin_test_checks(test_kernel_write_nochange, test_kernel_read);
+	do {
+		match_expect = report_matches(&expect);
+	} while (!end_test_checks(match_expect));
+	if (IS_ENABLED(CONFIG_KCSAN_REPORT_VALUE_CHANGE_ONLY))
+		KUNIT_EXPECT_FALSE(test, match_expect);
+	else
+		KUNIT_EXPECT_TRUE(test, match_expect);
+}
+
+/*
+ * Test that the rules where the KCSAN_REPORT_VALUE_CHANGE_ONLY option should
+ * never apply work.
+ */
+__no_kcsan
+static void test_novalue_change_exception(struct kunit *test)
+{
+	const struct expect_report expect = {
+		.access = {
+			{ test_kernel_write_nochange_rcu, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
+			{ test_kernel_read, &test_var, sizeof(test_var), 0 },
+		},
+	};
+	bool match_expect = false;
+
+	begin_test_checks(test_kernel_write_nochange_rcu, test_kernel_read);
+	do {
+		match_expect = report_matches(&expect);
+	} while (!end_test_checks(match_expect));
+	KUNIT_EXPECT_TRUE(test, match_expect);
+}
+
+/* Test that data races of unknown origin are reported. */
+__no_kcsan
+static void test_unknown_origin(struct kunit *test)
+{
+	const struct expect_report expect = {
+		.access = {
+			{ test_kernel_read, &test_var, sizeof(test_var), 0 },
+			{ NULL },
+		},
+	};
+	bool match_expect = false;
+
+	begin_test_checks(test_kernel_write_uninstrumented, test_kernel_read);
+	do {
+		match_expect = report_matches(&expect);
+	} while (!end_test_checks(match_expect));
+	if (IS_ENABLED(CONFIG_KCSAN_REPORT_RACE_UNKNOWN_ORIGIN))
+		KUNIT_EXPECT_TRUE(test, match_expect);
+	else
+		KUNIT_EXPECT_FALSE(test, match_expect);
+}
+
+/* Test KCSAN_ASSUME_PLAIN_WRITES_ATOMIC if it is selected. */
+__no_kcsan
+static void test_write_write_assume_atomic(struct kunit *test)
+{
+	const struct expect_report expect = {
+		.access = {
+			{ test_kernel_write, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
+			{ test_kernel_write, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
+		},
+	};
+	bool match_expect = false;
+
+	begin_test_checks(test_kernel_write, test_kernel_write);
+	do {
+		sink_value(READ_ONCE(test_var)); /* induce value-change */
+		match_expect = report_matches(&expect);
+	} while (!end_test_checks(match_expect));
+	if (IS_ENABLED(CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC))
+		KUNIT_EXPECT_FALSE(test, match_expect);
+	else
+		KUNIT_EXPECT_TRUE(test, match_expect);
+}
+
+/*
+ * Test that data races with writes larger than word-size are always reported,
+ * even if KCSAN_ASSUME_PLAIN_WRITES_ATOMIC is selected.
+ */
+__no_kcsan
+static void test_write_write_struct(struct kunit *test)
+{
+	const struct expect_report expect = {
+		.access = {
+			{ test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
+			{ test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
+		},
+	};
+	bool match_expect = false;
+
+	begin_test_checks(test_kernel_write_struct, test_kernel_write_struct);
+	do {
+		match_expect = report_matches(&expect);
+	} while (!end_test_checks(match_expect));
+	KUNIT_EXPECT_TRUE(test, match_expect);
+}
+
+/*
+ * Test that data races where only one write is larger than word-size are always
+ * reported, even if KCSAN_ASSUME_PLAIN_WRITES_ATOMIC is selected.
+ */
+__no_kcsan
+static void test_write_write_struct_part(struct kunit *test)
+{
+	const struct expect_report expect = {
+		.access = {
+			{ test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
+			{ test_kernel_write_struct_part, &test_struct.val[3], sizeof(test_struct.val[3]), KCSAN_ACCESS_WRITE },
+		},
+	};
+	bool match_expect = false;
+
+	begin_test_checks(test_kernel_write_struct, test_kernel_write_struct_part);
+	do {
+		match_expect = report_matches(&expect);
+	} while (!end_test_checks(match_expect));
+	KUNIT_EXPECT_TRUE(test, match_expect);
+}
+
+/* Test that races with atomic accesses never result in reports. */
+__no_kcsan
+static void test_read_atomic_write_atomic(struct kunit *test)
+{
+	bool match_never = false;
+
+	begin_test_checks(test_kernel_read_atomic, test_kernel_write_atomic);
+	do {
+		match_never = report_available();
+	} while (!end_test_checks(match_never));
+	KUNIT_EXPECT_FALSE(test, match_never);
+}
+
+/* Test that a race with an atomic and plain access result in reports. */
+__no_kcsan
+static void test_read_plain_atomic_write(struct kunit *test)
+{
+	const struct expect_report expect = {
+		.access = {
+			{ test_kernel_read, &test_var, sizeof(test_var), 0 },
+			{ test_kernel_write_atomic, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC },
+		},
+	};
+	bool match_expect = false;
+
+	if (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS))
+		return;
+
+	begin_test_checks(test_kernel_read, test_kernel_write_atomic);
+	do {
+		match_expect = report_matches(&expect);
+	} while (!end_test_checks(match_expect));
+	KUNIT_EXPECT_TRUE(test, match_expect);
+}
+
+/* Zero-sized accesses should never cause data race reports. */
+__no_kcsan
+static void test_zero_size_access(struct kunit *test)
+{
+	const struct expect_report expect = {
+		.access = {
+			{ test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
+			{ test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
+		},
+	};
+	const struct expect_report never = {
+		.access = {
+			{ test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
+			{ test_kernel_read_struct_zero_size, &test_struct.val[3], 0, 0 },
+		},
+	};
+	bool match_expect = false;
+	bool match_never = false;
+
+	begin_test_checks(test_kernel_write_struct, test_kernel_read_struct_zero_size);
+	do {
+		match_expect |= report_matches(&expect);
+		match_never = report_matches(&never);
+	} while (!end_test_checks(match_never));
+	KUNIT_EXPECT_TRUE(test, match_expect); /* Sanity check. */
+	KUNIT_EXPECT_FALSE(test, match_never);
+}
+
+/* Test the data_race() macro. */
+__no_kcsan
+static void test_data_race(struct kunit *test)
+{
+	bool match_never = false;
+
+	begin_test_checks(test_kernel_data_race, test_kernel_data_race);
+	do {
+		match_never = report_available();
+	} while (!end_test_checks(match_never));
+	KUNIT_EXPECT_FALSE(test, match_never);
+}
+
+__no_kcsan
+static void test_assert_exclusive_writer(struct kunit *test)
+{
+	const struct expect_report expect = {
+		.access = {
+			{ test_kernel_assert_writer, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT },
+			{ test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
+		},
+	};
+	bool match_expect = false;
+
+	begin_test_checks(test_kernel_assert_writer, test_kernel_write_nochange);
+	do {
+		match_expect = report_matches(&expect);
+	} while (!end_test_checks(match_expect));
+	KUNIT_EXPECT_TRUE(test, match_expect);
+}
+
+__no_kcsan
+static void test_assert_exclusive_access(struct kunit *test)
+{
+	const struct expect_report expect = {
+		.access = {
+			{ test_kernel_assert_access, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE },
+			{ test_kernel_read, &test_var, sizeof(test_var), 0 },
+		},
+	};
+	bool match_expect = false;
+
+	begin_test_checks(test_kernel_assert_access, test_kernel_read);
+	do {
+		match_expect = report_matches(&expect);
+	} while (!end_test_checks(match_expect));
+	KUNIT_EXPECT_TRUE(test, match_expect);
+}
+
+__no_kcsan
+static void test_assert_exclusive_access_writer(struct kunit *test)
+{
+	const struct expect_report expect_access_writer = {
+		.access = {
+			{ test_kernel_assert_access, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE },
+			{ test_kernel_assert_writer, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT },
+		},
+	};
+	const struct expect_report expect_access_access = {
+		.access = {
+			{ test_kernel_assert_access, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE },
+			{ test_kernel_assert_access, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE },
+		},
+	};
+	const struct expect_report never = {
+		.access = {
+			{ test_kernel_assert_writer, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT },
+			{ test_kernel_assert_writer, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT },
+		},
+	};
+	bool match_expect_access_writer = false;
+	bool match_expect_access_access = false;
+	bool match_never = false;
+
+	begin_test_checks(test_kernel_assert_access, test_kernel_assert_writer);
+	do {
+		match_expect_access_writer |= report_matches(&expect_access_writer);
+		match_expect_access_access |= report_matches(&expect_access_access);
+		match_never |= report_matches(&never);
+	} while (!end_test_checks(match_never));
+	KUNIT_EXPECT_TRUE(test, match_expect_access_writer);
+	KUNIT_EXPECT_TRUE(test, match_expect_access_access);
+	KUNIT_EXPECT_FALSE(test, match_never);
+}
+
+__no_kcsan
+static void test_assert_exclusive_bits_change(struct kunit *test)
+{
+	const struct expect_report expect = {
+		.access = {
+			{ test_kernel_assert_bits_change, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT },
+			{ test_kernel_change_bits, &test_var, sizeof(test_var),
+				KCSAN_ACCESS_WRITE | (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS) ? 0 : KCSAN_ACCESS_ATOMIC) },
+		},
+	};
+	bool match_expect = false;
+
+	begin_test_checks(test_kernel_assert_bits_change, test_kernel_change_bits);
+	do {
+		match_expect = report_matches(&expect);
+	} while (!end_test_checks(match_expect));
+	KUNIT_EXPECT_TRUE(test, match_expect);
+}
+
+__no_kcsan
+static void test_assert_exclusive_bits_nochange(struct kunit *test)
+{
+	bool match_never = false;
+
+	begin_test_checks(test_kernel_assert_bits_nochange, test_kernel_change_bits);
+	do {
+		match_never = report_available();
+	} while (!end_test_checks(match_never));
+	KUNIT_EXPECT_FALSE(test, match_never);
+}
+
+__no_kcsan
+static void test_assert_exclusive_writer_scoped(struct kunit *test)
+{
+	const struct expect_report expect_start = {
+		.access = {
+			{ test_kernel_assert_writer_scoped, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_SCOPED },
+			{ test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
+		},
+	};
+	const struct expect_report expect_anywhere = {
+		.access = {
+			{ test_enter_scope, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_SCOPED },
+			{ test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
+		},
+	};
+	bool match_expect_start = false;
+	bool match_expect_anywhere = false;
+
+	begin_test_checks(test_kernel_assert_writer_scoped, test_kernel_write_nochange);
+	do {
+		match_expect_start |= report_matches(&expect_start);
+		match_expect_anywhere |= report_matches(&expect_anywhere);
+	} while (!end_test_checks(match_expect_start && match_expect_anywhere));
+	KUNIT_EXPECT_TRUE(test, match_expect_start);
+	KUNIT_EXPECT_TRUE(test, match_expect_anywhere);
+}
+
+__no_kcsan
+static void test_assert_exclusive_access_scoped(struct kunit *test)
+{
+	const struct expect_report expect_start1 = {
+		.access = {
+			{ test_kernel_assert_access_scoped, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_SCOPED },
+			{ test_kernel_read, &test_var, sizeof(test_var), 0 },
+		},
+	};
+	const struct expect_report expect_start2 = {
+		.access = { expect_start1.access[0], expect_start1.access[0] },
+	};
+	const struct expect_report expect_inscope = {
+		.access = {
+			{ test_enter_scope, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_SCOPED },
+			{ test_kernel_read, &test_var, sizeof(test_var), 0 },
+		},
+	};
+	bool match_expect_start = false;
+	bool match_expect_inscope = false;
+
+	begin_test_checks(test_kernel_assert_access_scoped, test_kernel_read);
+	end_time += msecs_to_jiffies(1000); /* This test requires a bit more time. */
+	do {
+		match_expect_start |= report_matches(&expect_start1) || report_matches(&expect_start2);
+		match_expect_inscope |= report_matches(&expect_inscope);
+	} while (!end_test_checks(match_expect_start && match_expect_inscope));
+	KUNIT_EXPECT_TRUE(test, match_expect_start);
+	KUNIT_EXPECT_TRUE(test, match_expect_inscope);
+}
+
+/* Test that racing accesses in seqlock critical sections are not reported. */
+__no_kcsan
+static void test_seqlock_noreport(struct kunit *test)
+{
+	bool match_never = false;
+
+	begin_test_checks(test_kernel_seqlock_reader, test_kernel_seqlock_writer);
+	do {
+		match_never = report_available();
+	} while (!end_test_checks(match_never));
+	KUNIT_EXPECT_FALSE(test, match_never);
+}
+
+/*
+ * Each test case is run with different numbers of threads. Until KUnit supports
+ * passing arguments for each test case, we encode #threads in the test case
+ * name (read by get_num_threads()). [The '-' was chosen as a stylistic
+ * preference to separate test name and #threads.]
+ *
+ * The thread counts are chosen to cover potentially interesting boundaries and
+ * corner cases (range 2-5), and then stress the system with larger counts.
+ */
+#define KCSAN_KUNIT_CASE(test_name)                                            \
+	{ .run_case = test_name, .name = #test_name "-02" },                   \
+	{ .run_case = test_name, .name = #test_name "-03" },                   \
+	{ .run_case = test_name, .name = #test_name "-04" },                   \
+	{ .run_case = test_name, .name = #test_name "-05" },                   \
+	{ .run_case = test_name, .name = #test_name "-08" },                   \
+	{ .run_case = test_name, .name = #test_name "-16" }
+
+static struct kunit_case kcsan_test_cases[] = {
+	KCSAN_KUNIT_CASE(test_basic),
+	KCSAN_KUNIT_CASE(test_concurrent_races),
+	KCSAN_KUNIT_CASE(test_novalue_change),
+	KCSAN_KUNIT_CASE(test_novalue_change_exception),
+	KCSAN_KUNIT_CASE(test_unknown_origin),
+	KCSAN_KUNIT_CASE(test_write_write_assume_atomic),
+	KCSAN_KUNIT_CASE(test_write_write_struct),
+	KCSAN_KUNIT_CASE(test_write_write_struct_part),
+	KCSAN_KUNIT_CASE(test_read_atomic_write_atomic),
+	KCSAN_KUNIT_CASE(test_read_plain_atomic_write),
+	KCSAN_KUNIT_CASE(test_zero_size_access),
+	KCSAN_KUNIT_CASE(test_data_race),
+	KCSAN_KUNIT_CASE(test_assert_exclusive_writer),
+	KCSAN_KUNIT_CASE(test_assert_exclusive_access),
+	KCSAN_KUNIT_CASE(test_assert_exclusive_access_writer),
+	KCSAN_KUNIT_CASE(test_assert_exclusive_bits_change),
+	KCSAN_KUNIT_CASE(test_assert_exclusive_bits_nochange),
+	KCSAN_KUNIT_CASE(test_assert_exclusive_writer_scoped),
+	KCSAN_KUNIT_CASE(test_assert_exclusive_access_scoped),
+	KCSAN_KUNIT_CASE(test_seqlock_noreport),
+	{},
+};
+
+/* ===== End test cases ===== */
+
+/* Get number of threads encoded in test name. */
+static bool __no_kcsan
+get_num_threads(const char *test, int *nthreads)
+{
+	int len = strlen(test);
+
+	if (WARN_ON(len < 3))
+		return false;
+
+	*nthreads = test[len - 1] - '0';
+	*nthreads += (test[len - 2] - '0') * 10;
+
+	if (WARN_ON(*nthreads < 0))
+		return false;
+
+	return true;
+}
+
+/* Concurrent accesses from interrupts. */
+__no_kcsan
+static void access_thread_timer(struct timer_list *timer)
+{
+	static atomic_t cnt = ATOMIC_INIT(0);
+	unsigned int idx;
+	void (*func)(void);
+
+	idx = (unsigned int)atomic_inc_return(&cnt) % ARRAY_SIZE(access_kernels);
+	/* Acquire potential initialization. */
+	func = smp_load_acquire(&access_kernels[idx]);
+	if (func)
+		func();
+}
+
+/* The main loop for each thread. */
+__no_kcsan
+static int access_thread(void *arg)
+{
+	struct timer_list timer;
+	unsigned int cnt = 0;
+	unsigned int idx;
+	void (*func)(void);
+
+	timer_setup_on_stack(&timer, access_thread_timer, 0);
+	do {
+		might_sleep();
+
+		if (!timer_pending(&timer))
+			mod_timer(&timer, jiffies + 1);
+		else {
+			/* Iterate through all kernels. */
+			idx = cnt++ % ARRAY_SIZE(access_kernels);
+			/* Acquire potential initialization. */
+			func = smp_load_acquire(&access_kernels[idx]);
+			if (func)
+				func();
+		}
+	} while (!torture_must_stop());
+	del_timer_sync(&timer);
+	destroy_timer_on_stack(&timer);
+
+	torture_kthread_stopping("access_thread");
+	return 0;
+}
+
+__no_kcsan
+static int test_init(struct kunit *test)
+{
+	unsigned long flags;
+	int nthreads;
+	int i;
+
+	spin_lock_irqsave(&observed.lock, flags);
+	for (i = 0; i < ARRAY_SIZE(observed.lines); ++i)
+		observed.lines[i][0] = '\0';
+	observed.nlines = 0;
+	spin_unlock_irqrestore(&observed.lock, flags);
+
+	if (!torture_init_begin((char *)test->name, 1))
+		return -EBUSY;
+
+	if (!get_num_threads(test->name, &nthreads))
+		goto err;
+
+	if (WARN_ON(threads))
+		goto err;
+
+	for (i = 0; i < ARRAY_SIZE(access_kernels); ++i) {
+		if (WARN_ON(access_kernels[i]))
+			goto err;
+	}
+
+	if (!IS_ENABLED(CONFIG_PREEMPT) || !IS_ENABLED(CONFIG_KCSAN_INTERRUPT_WATCHER)) {
+		/*
+		 * Without any preemption, keep 2 CPUs free for other tasks, one
+		 * of which is the main test case function checking for
+		 * completion or failure.
+		 */
+		const int min_unused_cpus = IS_ENABLED(CONFIG_PREEMPT_NONE) ? 2 : 0;
+		const int min_required_cpus = 2 + min_unused_cpus;
+
+		if (num_online_cpus() < min_required_cpus) {
+			pr_err("%s: too few online CPUs (%u < %d) for test",
+			       test->name, num_online_cpus(), min_required_cpus);
+			goto err;
+		} else if (nthreads > num_online_cpus() - min_unused_cpus) {
+			nthreads = num_online_cpus() - min_unused_cpus;
+			pr_warn("%s: limiting number of threads to %d\n",
+				test->name, nthreads);
+		}
+	}
+
+	if (nthreads) {
+		threads = kcalloc(nthreads + 1, sizeof(struct task_struct *),
+				  GFP_KERNEL);
+		if (WARN_ON(!threads))
+			goto err;
+
+		threads[nthreads] = NULL;
+		for (i = 0; i < nthreads; ++i) {
+			if (torture_create_kthread(access_thread, NULL,
+						   threads[i]))
+				goto err;
+		}
+	}
+
+	torture_init_end();
+
+	return 0;
+
+err:
+	kfree(threads);
+	threads = NULL;
+	torture_init_end();
+	return -EINVAL;
+}
+
+__no_kcsan
+static void test_exit(struct kunit *test)
+{
+	struct task_struct **stop_thread;
+	int i;
+
+	if (torture_cleanup_begin())
+		return;
+
+	for (i = 0; i < ARRAY_SIZE(access_kernels); ++i)
+		WRITE_ONCE(access_kernels[i], NULL);
+
+	if (threads) {
+		for (stop_thread = threads; *stop_thread; stop_thread++)
+			torture_stop_kthread(reader_thread, *stop_thread);
+
+		kfree(threads);
+		threads = NULL;
+	}
+
+	torture_cleanup_end();
+}
+
+static struct kunit_suite kcsan_test_suite = {
+	.name = "kcsan-test",
+	.test_cases = kcsan_test_cases,
+	.init = test_init,
+	.exit = test_exit,
+};
+static struct kunit_suite *kcsan_test_suites[] = { &kcsan_test_suite, NULL };
+
+__no_kcsan
+static void register_tracepoints(struct tracepoint *tp, void *ignore)
+{
+	check_trace_callback_type_console(probe_console);
+	if (!strcmp(tp->name, "console"))
+		WARN_ON(tracepoint_probe_register(tp, probe_console, NULL));
+}
+
+__no_kcsan
+static void unregister_tracepoints(struct tracepoint *tp, void *ignore)
+{
+	if (!strcmp(tp->name, "console"))
+		tracepoint_probe_unregister(tp, probe_console, NULL);
+}
+
+/*
+ * We only want to do tracepoints setup and teardown once, therefore we have to
+ * customize the init and exit functions and cannot rely on kunit_test_suite().
+ */
+static int __init kcsan_test_init(void)
+{
+	/*
+	 * Because we want to be able to build the test as a module, we need to
+	 * iterate through all known tracepoints, since the static registration
+	 * won't work here.
+	 */
+	for_each_kernel_tracepoint(register_tracepoints, NULL);
+	return __kunit_test_suites_init(kcsan_test_suites);
+}
+
+static void kcsan_test_exit(void)
+{
+	__kunit_test_suites_exit(kcsan_test_suites);
+	for_each_kernel_tracepoint(unregister_tracepoints, NULL);
+	tracepoint_synchronize_unregister();
+}
+
+late_initcall(kcsan_test_init);
+module_exit(kcsan_test_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Marco Elver <elver@google.com>");
diff --git a/lib/Kconfig.kcsan b/lib/Kconfig.kcsan
index 5ee88e5..3f3b5bc 100644
--- a/lib/Kconfig.kcsan
+++ b/lib/Kconfig.kcsan
@@ -59,7 +59,28 @@ config KCSAN_SELFTEST
 	bool "Perform short selftests on boot"
 	default y
 	help
-	  Run KCSAN selftests on boot. On test failure, causes the kernel to panic.
+	  Run KCSAN selftests on boot. On test failure, causes the kernel to
+	  panic. Recommended to be enabled, ensuring critical functionality
+	  works as intended.
+
+config KCSAN_TEST
+	tristate "KCSAN test for integrated runtime behaviour"
+	depends on TRACEPOINTS && KUNIT
+	select TORTURE_TEST
+	help
+	  KCSAN test focusing on behaviour of the integrated runtime. Tests
+	  various race scenarios, and verifies the reports generated to
+	  console. Makes use of KUnit for test organization, and the Torture
+	  framework for test thread control.
+
+	  Each test case may run at least up to KCSAN_REPORT_ONCE_IN_MS
+	  milliseconds. Test run duration may be optimized by building the
+	  kernel and KCSAN test with KCSAN_REPORT_ONCE_IN_MS set to a lower
+	  than default value.
+
+	  Say Y here if you want the test to be built into the kernel and run
+	  during boot; say M if you want the test to build as a module; say N
+	  if you are unsure.
 
 config KCSAN_EARLY_ENABLE
 	bool "Early enable during boot"
-- 
2.9.5

[PATCH tip/core/rcu 05/10] locking/osq_lock: Annotate a data race in osq_lock

[paulmck]

From: Qian Cai <cai@lca.pw>

The prev->next pointer can be accessed concurrently as noticed by KCSAN:

 write (marked) to 0xffff9d3370dbbe40 of 8 bytes by task 3294 on cpu 107:
  osq_lock+0x25f/0x350
  osq_wait_next at kernel/locking/osq_lock.c:79
  (inlined by) osq_lock at kernel/locking/osq_lock.c:185
  rwsem_optimistic_spin
  <snip>

 read to 0xffff9d3370dbbe40 of 8 bytes by task 3398 on cpu 100:
  osq_lock+0x196/0x350
  osq_lock at kernel/locking/osq_lock.c:157
  rwsem_optimistic_spin
  <snip>

Since the write only stores NULL to prev->next and the read tests if
prev->next equals to this_cpu_ptr(&osq_node). Even if the value is
shattered, the code is still working correctly. Thus, mark it as an
intentional data race using the data_race() macro.

Signed-off-by: Qian Cai <cai@lca.pw>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/locking/osq_lock.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/locking/osq_lock.c b/kernel/locking/osq_lock.c
index 1f77349..1de006e 100644
--- a/kernel/locking/osq_lock.c
+++ b/kernel/locking/osq_lock.c
@@ -154,7 +154,11 @@ bool osq_lock(struct optimistic_spin_queue *lock)
 	 */
 
 	for (;;) {
-		if (prev->next == node &&
+		/*
+		 * cpu_relax() below implies a compiler barrier which would
+		 * prevent this comparison being optimized away.
+		 */
+		if (data_race(prev->next) == node &&
 		    cmpxchg(&prev->next, node, NULL) == node)
 			break;
 
-- 
2.9.5

[PATCH tip/core/rcu 06/10] kcsan: Prefer '__no_kcsan inline' in test

[paulmck]

From: Marco Elver <elver@google.com>

Instead of __no_kcsan_or_inline, prefer '__no_kcsan inline' in test --
this is in case we decide to remove __no_kcsan_or_inline.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/kcsan/kcsan-test.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/kcsan/kcsan-test.c b/kernel/kcsan/kcsan-test.c
index a8c1150..3af420a 100644
--- a/kernel/kcsan/kcsan-test.c
+++ b/kernel/kcsan/kcsan-test.c
@@ -43,7 +43,7 @@ static struct {
 };
 
 /* Setup test checking loop. */
-static __no_kcsan_or_inline void
+static __no_kcsan inline void
 begin_test_checks(void (*func1)(void), void (*func2)(void))
 {
 	kcsan_disable_current();
@@ -60,7 +60,7 @@ begin_test_checks(void (*func1)(void), void (*func2)(void))
 }
 
 /* End test checking loop. */
-static __no_kcsan_or_inline bool
+static __no_kcsan inline bool
 end_test_checks(bool stop)
 {
 	if (!stop && time_before(jiffies, end_time)) {
-- 
2.9.5

[PATCH tip/core/rcu 07/10] kcsan: Silence -Wmissing-prototypes warning with W=1

[paulmck]

From: Marco Elver <elver@google.com>

The functions here should not be forward declared for explicit use
elsewhere in the kernel, as they should only be emitted by the compiler
due to sanitizer instrumentation.  Add forward declarations a line above
their definition to shut up warnings in W=1 builds.

Link: https://lkml.kernel.org/r/202006060103.jSCpnV1g%lkp@intel.com
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/kcsan/core.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c
index 15f6794..1866baf 100644
--- a/kernel/kcsan/core.c
+++ b/kernel/kcsan/core.c
@@ -754,6 +754,7 @@ EXPORT_SYMBOL(__kcsan_check_access);
  */
 
 #define DEFINE_TSAN_READ_WRITE(size)                                           \
+	void __tsan_read##size(void *ptr);                                     \
 	void __tsan_read##size(void *ptr)                                      \
 	{                                                                      \
 		check_access(ptr, size, 0);                                    \
@@ -762,6 +763,7 @@ EXPORT_SYMBOL(__kcsan_check_access);
 	void __tsan_unaligned_read##size(void *ptr)                            \
 		__alias(__tsan_read##size);                                    \
 	EXPORT_SYMBOL(__tsan_unaligned_read##size);                            \
+	void __tsan_write##size(void *ptr);                                    \
 	void __tsan_write##size(void *ptr)                                     \
 	{                                                                      \
 		check_access(ptr, size, KCSAN_ACCESS_WRITE);                   \
@@ -777,12 +779,14 @@ DEFINE_TSAN_READ_WRITE(4);
 DEFINE_TSAN_READ_WRITE(8);
 DEFINE_TSAN_READ_WRITE(16);
 
+void __tsan_read_range(void *ptr, size_t size);
 void __tsan_read_range(void *ptr, size_t size)
 {
 	check_access(ptr, size, 0);
 }
 EXPORT_SYMBOL(__tsan_read_range);
 
+void __tsan_write_range(void *ptr, size_t size);
 void __tsan_write_range(void *ptr, size_t size)
 {
 	check_access(ptr, size, KCSAN_ACCESS_WRITE);
@@ -799,6 +803,7 @@ EXPORT_SYMBOL(__tsan_write_range);
  * the size-check of compiletime_assert_rwonce_type().
  */
 #define DEFINE_TSAN_VOLATILE_READ_WRITE(size)                                  \
+	void __tsan_volatile_read##size(void *ptr);                            \
 	void __tsan_volatile_read##size(void *ptr)                             \
 	{                                                                      \
 		const bool is_atomic = size <= sizeof(long long) &&            \
@@ -811,6 +816,7 @@ EXPORT_SYMBOL(__tsan_write_range);
 	void __tsan_unaligned_volatile_read##size(void *ptr)                   \
 		__alias(__tsan_volatile_read##size);                           \
 	EXPORT_SYMBOL(__tsan_unaligned_volatile_read##size);                   \
+	void __tsan_volatile_write##size(void *ptr);                           \
 	void __tsan_volatile_write##size(void *ptr)                            \
 	{                                                                      \
 		const bool is_atomic = size <= sizeof(long long) &&            \
@@ -836,14 +842,17 @@ DEFINE_TSAN_VOLATILE_READ_WRITE(16);
  * The below are not required by KCSAN, but can still be emitted by the
  * compiler.
  */
+void __tsan_func_entry(void *call_pc);
 void __tsan_func_entry(void *call_pc)
 {
 }
 EXPORT_SYMBOL(__tsan_func_entry);
+void __tsan_func_exit(void);
 void __tsan_func_exit(void)
 {
 }
 EXPORT_SYMBOL(__tsan_func_exit);
+void __tsan_init(void);
 void __tsan_init(void)
 {
 }
-- 
2.9.5

[PATCH tip/core/rcu 08/10] kcsan: Rename test.c to selftest.c

[paulmck]

From: Marco Elver <elver@google.com>

Rename 'test.c' to 'selftest.c' to better reflect its purpose (Kconfig
variable and code inside already match this). This is to avoid confusion
with the test suite module in 'kcsan-test.c'.

No functional change.

Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/kcsan/Makefile               | 2 +-
 kernel/kcsan/{test.c => selftest.c} | 0
 2 files changed, 1 insertion(+), 1 deletion(-)
 rename kernel/kcsan/{test.c => selftest.c} (100%)

diff --git a/kernel/kcsan/Makefile b/kernel/kcsan/Makefile
index 14533cf..092ce58 100644
--- a/kernel/kcsan/Makefile
+++ b/kernel/kcsan/Makefile
@@ -11,7 +11,7 @@ CFLAGS_core.o := $(call cc-option,-fno-conserve-stack,) \
 	$(call cc-option,-fno-stack-protector,)
 
 obj-y := core.o debugfs.o report.o
-obj-$(CONFIG_KCSAN_SELFTEST) += test.o
+obj-$(CONFIG_KCSAN_SELFTEST) += selftest.o
 
 CFLAGS_kcsan-test.o := $(CFLAGS_KCSAN) -g -fno-omit-frame-pointer
 obj-$(CONFIG_KCSAN_TEST) += kcsan-test.o
diff --git a/kernel/kcsan/test.c b/kernel/kcsan/selftest.c
similarity index 100%
rename from kernel/kcsan/test.c
rename to kernel/kcsan/selftest.c
-- 
2.9.5

[PATCH tip/core/rcu 09/10] kcsan: Remove existing special atomic rules

[paulmck]

From: Marco Elver <elver@google.com>

Remove existing special atomic rules from kcsan_is_atomic_special()
because they are no longer needed. Since we rely on the compiler
emitting instrumentation distinguishing volatile accesses, the rules
have become redundant.

Let's keep kcsan_is_atomic_special() around, so that we have an obvious
place to add special rules should the need arise in future.

Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/kcsan/atomic.h | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/kernel/kcsan/atomic.h b/kernel/kcsan/atomic.h
index be9e625..75fe701 100644
--- a/kernel/kcsan/atomic.h
+++ b/kernel/kcsan/atomic.h
@@ -3,8 +3,7 @@
 #ifndef _KERNEL_KCSAN_ATOMIC_H
 #define _KERNEL_KCSAN_ATOMIC_H
 
-#include <linux/jiffies.h>
-#include <linux/sched.h>
+#include <linux/types.h>
 
 /*
  * Special rules for certain memory where concurrent conflicting accesses are
@@ -13,8 +12,7 @@
  */
 static bool kcsan_is_atomic_special(const volatile void *ptr)
 {
-	/* volatile globals that have been observed in data races. */
-	return ptr == &jiffies || ptr == &current->state;
+	return false;
 }
 
 #endif /* _KERNEL_KCSAN_ATOMIC_H */
-- 
2.9.5

[PATCH tip/core/rcu 10/10] kcsan: Add jiffies test to test suite

[paulmck]

From: Marco Elver <elver@google.com>

Add a test that KCSAN nor the compiler gets confused about accesses to
jiffies on different architectures.

Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/kcsan/kcsan-test.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/kernel/kcsan/kcsan-test.c b/kernel/kcsan/kcsan-test.c
index 3af420a..fed6fcb 100644
--- a/kernel/kcsan/kcsan-test.c
+++ b/kernel/kcsan/kcsan-test.c
@@ -366,6 +366,11 @@ static noinline void test_kernel_read_struct_zero_size(void)
 	kcsan_check_read(&test_struct.val[3], 0);
 }
 
+static noinline void test_kernel_jiffies_reader(void)
+{
+	sink_value((long)jiffies);
+}
+
 static noinline void test_kernel_seqlock_reader(void)
 {
 	unsigned int seq;
@@ -817,6 +822,23 @@ static void test_assert_exclusive_access_scoped(struct kunit *test)
 	KUNIT_EXPECT_TRUE(test, match_expect_inscope);
 }
 
+/*
+ * jiffies is special (declared to be volatile) and its accesses are typically
+ * not marked; this test ensures that the compiler nor KCSAN gets confused about
+ * jiffies's declaration on different architectures.
+ */
+__no_kcsan
+static void test_jiffies_noreport(struct kunit *test)
+{
+	bool match_never = false;
+
+	begin_test_checks(test_kernel_jiffies_reader, test_kernel_jiffies_reader);
+	do {
+		match_never = report_available();
+	} while (!end_test_checks(match_never));
+	KUNIT_EXPECT_FALSE(test, match_never);
+}
+
 /* Test that racing accesses in seqlock critical sections are not reported. */
 __no_kcsan
 static void test_seqlock_noreport(struct kunit *test)
@@ -867,6 +889,7 @@ static struct kunit_case kcsan_test_cases[] = {
 	KCSAN_KUNIT_CASE(test_assert_exclusive_bits_nochange),
 	KCSAN_KUNIT_CASE(test_assert_exclusive_writer_scoped),
 	KCSAN_KUNIT_CASE(test_assert_exclusive_access_scoped),
+	KCSAN_KUNIT_CASE(test_jiffies_noreport),
 	KCSAN_KUNIT_CASE(test_seqlock_noreport),
 	{},
 };
-- 
2.9.5