[PATCH tip/core/rcu 01/19] scftorture: Add smp_call_function() torture test

paulmck
2020-08-31T18:09:47Z

This commit adds an smp_call_function() torture test that repeatedly
invokes this function and complains if things go badly awry.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
Documentation/admin-guide/kernel-parameters.txt | 92 +++++++
kernel/Makefile | 2 +
kernel/scftorture.c | 350 ++++++++++++++++++++++++
lib/Kconfig.debug | 10 +
4 files changed, 454 insertions(+)
create mode 100644 kernel/scftorture.c

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index bdc1f33..91a5638 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4637,6 +4637,98 @@
Format: integer between 0 and 10
Default is 0.

+ scftorture.holdoff= [KNL]
+ Number of seconds to hold off before starting
+ test. Defaults to zero for module insertion and
+ to 10 seconds for built-in smp_call_function()
+ tests.
+
+ scftorture.longwait= [KNL]
+ Request ridiculously long waits randomly selected
+ up to the chosen limit in seconds. Zero (the
+ default) disables this feature. Please note
+ that requesting even small non-zero numbers of
+ seconds can result in RCU CPU stall warnings,
+ softlockup complaints, and so on.
+
+ scftorture.nthreads= [KNL]
+ Number of kthreads to spawn to invoke the
+ smp_call_function() family of functions.
+ The default of -1 specifies a number of kthreads
+ equal to the number of CPUs.
+
+ scftorture.onoff_holdoff= [KNL]
+ Number seconds to wait after the start of the
+ test before initiating CPU-hotplug operations.
+
+ scftorture.onoff_interval= [KNL]
+ Number seconds to wait between successive
+ CPU-hotplug operations. Specifying zero (which
+ is the default) disables CPU-hotplug operations.
+
+ scftorture.shutdown_secs= [KNL]
+ The number of seconds following the start of the
+ test after which to shut down the system. The
+ default of zero avoids shutting down the system.
+ Non-zero values are useful for automated tests.
+
+ scftorture.stat_interval= [KNL]
+ The number of seconds between outputting the
+ current test statistics to the console. A value
+ of zero disables statistics output.
+
+ scftorture.stutter_cpus= [KNL]
+ The number of jiffies to wait between each change
+ to the set of CPUs under test.
+
+ scftorture.use_cpus_read_lock= [KNL]
+ Use use_cpus_read_lock() instead of the default
+ preempt_disable() to disable CPU hotplug
+ while invoking one of the smp_call_function*()
+ functions.
+
+ scftorture.verbose= [KNL]
+ Enable additional printk() statements.
+
+ scftorture.weight_single= [KNL]
+ The probability weighting to use for the
+ smp_call_function_single() function with a zero
+ "wait" parameter. A value of -1 selects the
+ default if all other weights are -1. However,
+ if at least one weight has some other value, a
+ value of -1 will instead select a weight of zero.
+
+ scftorture.weight_single_wait= [KNL]
+ The probability weighting to use for the
+ smp_call_function_single() function with a
+ non-zero "wait" parameter. See weight_single.
+
+ scftorture.weight_many= [KNL]
+ The probability weighting to use for the
+ smp_call_function_many() function with a zero
+ "wait" parameter. See weight_single.
+ Note well that setting a high probability for
+ this weighting can place serious IPI load
+ on the system.
+
+ scftorture.weight_many_wait= [KNL]
+ The probability weighting to use for the
+ smp_call_function_many() function with a
+ non-zero "wait" parameter. See weight_single
+ and weight_many.
+
+ scftorture.weight_all= [KNL]
+ The probability weighting to use for the
+ smp_call_function_all() function with a zero
+ "wait" parameter. See weight_single and
+ weight_many.
+
+ scftorture.weight_all_wait= [KNL]
+ The probability weighting to use for the
+ smp_call_function_all() function with a
+ non-zero "wait" parameter. See weight_single
+ and weight_many.
+
skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
xtime_lock contention on larger systems, and/or RCU lock
contention on all systems with CONFIG_MAXSMP set.
diff --git a/kernel/Makefile b/kernel/Makefile
index 9a20016..c45f551 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -133,6 +133,8 @@ KASAN_SANITIZE_stackleak.o := n
KCSAN_SANITIZE_stackleak.o := n
KCOV_INSTRUMENT_stackleak.o := n

+obj-$(CONFIG_SCF_TORTURE_TEST) += scftorture.o
+
$(obj)/configs.o: $(obj)/config_data.gz

targets += config_data.gz
diff --git a/kernel/scftorture.c b/kernel/scftorture.c
new file mode 100644
index 0000000..44f1e49
--- /dev/null
+++ b/kernel/scftorture.c
@@ -0,0 +1,350 @@
+// SPDX-License-Identifier: GPL-2.0+
+//
+// Torture test for smp_call_function() and friends.
+//
+// Copyright (C) Facebook, 2020.
+//
+// Author: Paul E. McKenney <paulmck@kernel.org>
+
+#define pr_fmt(fmt) fmt
+
+#include <linux/atomic.h>
+#include <linux/bitops.h>
+#include <linux/completion.h>
+#include <linux/cpu.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/kthread.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/notifier.h>
+#include <linux/percpu.h>
+#include <linux/rcupdate.h>
+#include <linux/rcupdate_trace.h>
+#include <linux/reboot.h>
+#include <linux/sched.h>
+#include <linux/spinlock.h>
+#include <linux/smp.h>
+#include <linux/stat.h>
+#include <linux/srcu.h>
+#include <linux/slab.h>
+#include <linux/torture.h>
+#include <linux/types.h>
+
+#define SCFTORT_STRING "scftorture"
+#define SCFTORT_FLAG SCFTORT_STRING ": "
+
+#define SCFTORTOUT(s, x...) \
+ pr_alert(SCFTORT_FLAG s, ## x)
+
+#define VERBOSE_SCFTORTOUT(s, x...) \
+ do { if (verbose) pr_alert(SCFTORT_FLAG s, ## x); } while (0)
+
+#define VERBOSE_SCFTORTOUT_ERRSTRING(s, x...) \
+ do { if (verbose) pr_alert(SCFTORT_FLAG "!!! " s, ## x); } while (0)
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Paul E. McKenney <paulmck@kernel.org>");
+
+// Wait until there are multiple CPUs before starting test.
+torture_param(int, holdoff, IS_BUILTIN(CONFIG_SCF_TORTURE_TEST) ? 10 : 0,
+ "Holdoff time before test start (s)");
+torture_param(int, longwait, 0, "Include ridiculously long waits? (seconds)");
+torture_param(int, nthreads, -1, "# threads, defaults to -1 for all CPUs.");
+torture_param(int, onoff_holdoff, 0, "Time after boot before CPU hotplugs (s)");
+torture_param(int, onoff_interval, 0, "Time between CPU hotplugs (s), 0=disable");
+torture_param(int, shutdown_secs, 0, "Shutdown time (ms), <= zero to disable.");
+torture_param(int, stat_interval, 60, "Number of seconds between stats printk()s.");
+torture_param(int, stutter_cpus, 5, "Number of jiffies to change CPUs under test, 0=disable");
+torture_param(bool, use_cpus_read_lock, 0, "Use cpus_read_lock() to exclude CPU hotplug.");
+torture_param(int, verbose, 0, "Enable verbose debugging printk()s");
+torture_param(int, weight_single, -1, "Testing weight for single-CPU no-wait operations.");
+torture_param(int, weight_single_wait, -1, "Testing weight for single-CPU operations.");
+torture_param(int, weight_mult, -1, "Testing weight for multi-CPU no-wait operations.");
+torture_param(int, weight_mult_wait, -1, "Testing weight for multi-CPU operations.");
+torture_param(int, weight_all, -1, "Testing weight for all-CPU no-wait operations.");
+torture_param(int, weight_all_wait, -1, "Testing weight for all-CPU operations.");
+
+char *torture_type = "";
+
+#ifdef MODULE
+# define SCFTORT_SHUTDOWN 0
+#else
+# define SCFTORT_SHUTDOWN 1
+#endif
+
+torture_param(bool, shutdown, SCFTORT_SHUTDOWN, "Shutdown at end of torture test.");
+
+struct scf_statistics {
+ struct task_struct *task;
+ int cpu;
+ long long n_single;
+ long long n_single_wait;
+ long long n_multi;
+ long long n_multi_wait;
+ long long n_all;
+ long long n_all_wait;
+};
+
+static struct scf_statistics *scf_stats_p;
+static struct task_struct *scf_torture_stats_task;
+static DEFINE_PER_CPU(long long, scf_invoked_count);
+
+// Use to wait for all threads to start.
+static atomic_t n_started;
+static atomic_t n_errs;
+static bool scfdone;
+
+DEFINE_TORTURE_RANDOM_PERCPU(scf_torture_rand);
+
+// Print torture statistics. Caller must ensure serialization.
+static void scf_torture_stats_print(void)
+{
+ int cpu;
+ long long invoked_count = 0;
+ bool isdone = READ_ONCE(scfdone);
+
+ for_each_possible_cpu(cpu)
+ invoked_count += data_race(per_cpu(scf_invoked_count, cpu));
+ pr_alert("%s scf_invoked_count %s: %lld ",
+ SCFTORT_FLAG, isdone ? "VER" : "ver", invoked_count);
+ torture_onoff_stats();
+ pr_cont("\n");
+}
+
+// Periodically prints torture statistics, if periodic statistics printing
+// was specified via the stat_interval module parameter.
+static int
+scf_torture_stats(void *arg)
+{
+ VERBOSE_TOROUT_STRING("scf_torture_stats task started");
+ do {
+ schedule_timeout_interruptible(stat_interval * HZ);
+ scf_torture_stats_print();
+ torture_shutdown_absorb("scf_torture_stats");
+ } while (!torture_must_stop());
+ torture_kthread_stopping("scf_torture_stats");
+ return 0;
+}
+
+// Update statistics and occasionally burn up mass quantities of CPU time,
+// if told to do so via scftorture.longwait. Otherwise, occasionally burn
+// a little bit.
+static void scf_handler(void *unused)
+{
+ int i;
+ int j;
+ unsigned long r = torture_random(this_cpu_ptr(&scf_torture_rand));
+
+ this_cpu_inc(scf_invoked_count);
+ if (longwait <= 0) {
+ if (!(r & 0xffc0))
+ udelay(r & 0x3f);
+ return;
+ }
+ if (r & 0xfff)
+ return;
+ r = (r >> 12);
+ if (longwait <= 0) {
+ udelay((r & 0xff) + 1);
+ return;
+ }
+ r = r % longwait + 1;
+ for (i = 0; i < r; i++) {
+ for (j = 0; j < 1000; j++) {
+ udelay(1000);
+ cpu_relax();
+ }
+ }
+}
+
+// Randomly do an smp_call_function*() invocation.
+static void scftorture_invoke_one(struct scf_statistics *scfp,struct torture_random_state *trsp)
+{
+ if (use_cpus_read_lock)
+ cpus_read_lock();
+ else
+ preempt_disable();
+ scfp->n_all++;
+ smp_call_function(scf_handler, NULL, 0);
+ if (use_cpus_read_lock)
+ cpus_read_unlock();
+ else
+ preempt_enable();
+ if (!(torture_random(trsp) & 0xfff))
+ schedule_timeout_uninterruptible(1);
+}
+
+// SCF test kthread. Repeatedly does calls to members of the
+// smp_call_function() family of functions.
+static int scftorture_invoker(void *arg)
+{
+ DEFINE_TORTURE_RANDOM(rand);
+ struct scf_statistics *scfp = (struct scf_statistics *)arg;
+
+ VERBOSE_SCFTORTOUT("scftorture_invoker %d: task started", scfp->cpu);
+ set_cpus_allowed_ptr(current, cpumask_of(scfp->cpu % nr_cpu_ids));
+ set_user_nice(current, MAX_NICE);
+ if (holdoff)
+ schedule_timeout_interruptible(holdoff * HZ);
+
+ VERBOSE_SCFTORTOUT("scftorture_invoker %d: Waiting for all SCF torturers from cpu %d", scfp->cpu, smp_processor_id());
+
+ // Make sure that the CPU is affinitized appropriately during testing.
+ WARN_ON_ONCE(smp_processor_id() != scfp->cpu);
+
+ if (!atomic_dec_return(&n_started))
+ while (atomic_read_acquire(&n_started)) {
+ if (torture_must_stop()) {
+ VERBOSE_SCFTORTOUT("scftorture_invoker %d ended before starting", scfp->cpu);
+ goto end;
+ }
+ schedule_timeout_uninterruptible(1);
+ }
+
+ VERBOSE_SCFTORTOUT("scftorture_invoker %d started", scfp->cpu);
+
+ do {
+ scftorture_invoke_one(scfp, &rand);
+ } while (!torture_must_stop());
+
+ VERBOSE_SCFTORTOUT("scftorture_invoker %d ended", scfp->cpu);
+end:
+ torture_kthread_stopping("scftorture_invoker");
+ return 0;
+}
+
+static void
+scftorture_print_module_parms(const char *tag)
+{
+ pr_alert(SCFTORT_FLAG
+ "--- %s: verbose=%d holdoff=%d longwait=%d nthreads=%d onoff_holdoff=%d onoff_interval=%d shutdown_secs=%d stat_interval=%d stutter_cpus=%d use_cpus_read_lock=%d, weight_single=%d, weight_single_wait=%d, weight_mult=%d, weight_mult_wait=%d, weight_all=%d, weight_all_wait=%d\n", tag,
+ verbose, holdoff, longwait, nthreads, onoff_holdoff, onoff_interval, shutdown, stat_interval, stutter_cpus, use_cpus_read_lock, weight_single, weight_single_wait, weight_mult, weight_mult_wait, weight_all, weight_all_wait);
+}
+
+static void scf_cleanup_handler(void *unused)
+{
+}
+
+static void scf_torture_cleanup(void)
+{
+ int i;
+
+ if (torture_cleanup_begin())
+ return;
+
+ WRITE_ONCE(scfdone, true);
+ if (nthreads)
+ for (i = 0; i < nthreads; i++)
+ torture_stop_kthread("scftorture_invoker", scf_stats_p[i].task);
+ else
+ goto end;
+ kfree(scf_stats_p);
+ scf_stats_p = NULL;
+ smp_call_function(scf_cleanup_handler, NULL, 0);
+ torture_stop_kthread(scf_torture_stats, scf_torture_stats_task);
+ scf_torture_stats_print(); // -After- the stats thread is stopped!
+
+ if (atomic_read(&n_errs))
+ scftorture_print_module_parms("End of test: FAILURE");
+ else if (torture_onoff_failures())
+ scftorture_print_module_parms("End of test: LOCK_HOTPLUG");
+ else
+ scftorture_print_module_parms("End of test: SUCCESS");
+
+end:
+ torture_cleanup_end();
+}
+
+static int __init scf_torture_init(void)
+{
+ long i;
+ int firsterr = 0;
+
+ if (!torture_init_begin(SCFTORT_STRING, verbose))
+ return -EBUSY;
+
+ scftorture_print_module_parms("Start of test");
+
+ if (weight_single == -1 && weight_single_wait == -1 &&
+ weight_mult == -1 && weight_mult_wait == -1 &&
+ weight_all == -1 && weight_all_wait == -1) {
+ weight_single = 1;
+ weight_single_wait = 1;
+ weight_mult = 1;
+ weight_mult_wait = 1;
+ weight_all = 1;
+ weight_all_wait = 1;
+ } else {
+ if (weight_single == -1)
+ weight_single = 0;
+ if (weight_single_wait == -1)
+ weight_single_wait = 0;
+ if (weight_mult == -1)
+ weight_mult = 0;
+ if (weight_mult_wait == -1)
+ weight_mult_wait = 0;
+ if (weight_all == -1)
+ weight_all = 0;
+ if (weight_all_wait == -1)
+ weight_all_wait = 0;
+ }
+ if (weight_single == 0 && weight_single_wait == 0 &&
+ weight_mult == 0 && weight_mult_wait == 0 &&
+ weight_all == 0 && weight_all_wait == 0) {
+ firsterr = -EINVAL;
+ goto unwind;
+ }
+
+ if (onoff_interval > 0) {
+ firsterr = torture_onoff_init(onoff_holdoff * HZ, onoff_interval, NULL);
+ if (firsterr)
+ goto unwind;
+ }
+ if (shutdown_secs > 0) {
+ firsterr = torture_shutdown_init(shutdown_secs, scf_torture_cleanup);
+ if (firsterr)
+ goto unwind;
+ }
+
+ // Worker tasks invoking smp_call_function().
+ if (nthreads < 0)
+ nthreads = num_online_cpus();
+ scf_stats_p = kcalloc(nthreads, sizeof(scf_stats_p[0]), GFP_KERNEL);
+ if (!scf_stats_p) {
+ VERBOSE_SCFTORTOUT_ERRSTRING("out of memory");
+ firsterr = -ENOMEM;
+ goto unwind;
+ }
+
+ VERBOSE_SCFTORTOUT("Starting %d smp_call_function() threads\n", nthreads);
+
+ atomic_set(&n_started, nthreads);
+ for (i = 0; i < nthreads; i++) {
+ scf_stats_p[i].cpu = i;
+ firsterr = torture_create_kthread(scftorture_invoker, (void *)&scf_stats_p[i],
+ scf_stats_p[i].task);
+ if (firsterr)
+ goto unwind;
+ }
+ if (stat_interval > 0) {
+ firsterr = torture_create_kthread(scf_torture_stats, NULL, scf_torture_stats_task);
+ if (firsterr)
+ goto unwind;
+ }
+
+ torture_init_end();
+ return 0;
+
+unwind:
+ torture_init_end();
+ scf_torture_cleanup();
+ return firsterr;
+}
+
+module_init(scf_torture_init);
+module_exit(scf_torture_cleanup);
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index e068c3c..0c3a6c7 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1367,6 +1367,16 @@ config WW_MUTEX_SELFTEST
Say M if you want these self tests to build as a module.
Say N if you are unsure.

+config SCF_TORTURE_TEST
+ tristate "torture tests for smp_call_function*()"
+ depends on DEBUG_KERNEL
+ select TORTURE_TEST
+ help
+ This option provides a kernel module that runs torture tests
+ on the smp_call_function() family of primitives. The kernel
+ module may be built after the fact on the running kernel to
+ be tested, if desired.
+
endmenu # lock debugging

config TRACE_IRQFLAGS
--
2.9.5