Commit e9d338a0 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

scftorture: Add smp_call_function() torture test 



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

Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent 9123e3a7

Documentation/admin-guide/kernel-parameters.txt

+92 −0
Original line number Diff line number Diff line
@@ -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.

kernel/Makefile

+2 −0
Original line number Diff line number Diff line
@@ -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

kernel/scftorture.c

0 → 100644
+350 −0
Original line number Diff line number Diff line 
// 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);

lib/Kconfig.debug

+10 −0
Original line number Diff line number Diff line
@@ -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