lib/test_lockup.c - SHIFTPHONES/kernel/common - Gitiles

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Test module to generate lockups
  */
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/delay.h>
 #include <linux/sched.h>
 #include <linux/sched/signal.h>
 #include <linux/sched/clock.h>
 #include <linux/cpu.h>
 #include <linux/nmi.h>
 #include <linux/mm.h>
 #include <linux/uaccess.h>
 #include <linux/file.h>

 static unsigned int time_secs;
 module_param(time_secs, uint, 0600);
 MODULE_PARM_DESC(time_secs, "lockup time in seconds, default 0");

 static unsigned int time_nsecs;
 module_param(time_nsecs, uint, 0600);
 MODULE_PARM_DESC(time_nsecs, "nanoseconds part of lockup time, default 0");

 static unsigned int cooldown_secs;
 module_param(cooldown_secs, uint, 0600);
 MODULE_PARM_DESC(cooldown_secs, "cooldown time between iterations in seconds, default 0");

 static unsigned int cooldown_nsecs;
 module_param(cooldown_nsecs, uint, 0600);
 MODULE_PARM_DESC(cooldown_nsecs, "nanoseconds part of cooldown, default 0");

 static unsigned int iterations = 1;
 module_param(iterations, uint, 0600);
 MODULE_PARM_DESC(iterations, "lockup iterations, default 1");

 static bool all_cpus;
 module_param(all_cpus, bool, 0400);
 MODULE_PARM_DESC(all_cpus, "trigger lockup at all cpus at once");

 static int wait_state;
 static char *state = "R";
 module_param(state, charp, 0400);
 MODULE_PARM_DESC(state, "wait in 'R' running (default), 'D' uninterruptible, 'K' killable, 'S' interruptible state");

 static bool use_hrtimer;
 module_param(use_hrtimer, bool, 0400);
 MODULE_PARM_DESC(use_hrtimer, "use high-resolution timer for sleeping");

 static bool iowait;
 module_param(iowait, bool, 0400);
 MODULE_PARM_DESC(iowait, "account sleep time as iowait");

 static bool lock_read;
 module_param(lock_read, bool, 0400);
 MODULE_PARM_DESC(lock_read, "lock read-write locks for read");

 static bool lock_single;
 module_param(lock_single, bool, 0400);
 MODULE_PARM_DESC(lock_single, "acquire locks only at one cpu");

 static bool reacquire_locks;
 module_param(reacquire_locks, bool, 0400);
 MODULE_PARM_DESC(reacquire_locks, "release and reacquire locks/irq/preempt between iterations");

 static bool touch_softlockup;
 module_param(touch_softlockup, bool, 0600);
 MODULE_PARM_DESC(touch_softlockup, "touch soft-lockup watchdog between iterations");

 static bool touch_hardlockup;
 module_param(touch_hardlockup, bool, 0600);
 MODULE_PARM_DESC(touch_hardlockup, "touch hard-lockup watchdog between iterations");

 static bool call_cond_resched;
 module_param(call_cond_resched, bool, 0600);
 MODULE_PARM_DESC(call_cond_resched, "call cond_resched() between iterations");

 static bool measure_lock_wait;
 module_param(measure_lock_wait, bool, 0400);
 MODULE_PARM_DESC(measure_lock_wait, "measure lock wait time");

 static unsigned long lock_wait_threshold = ULONG_MAX;
 module_param(lock_wait_threshold, ulong, 0400);
 MODULE_PARM_DESC(lock_wait_threshold, "print lock wait time longer than this in nanoseconds, default off");

 static bool test_disable_irq;
 module_param_named(disable_irq, test_disable_irq, bool, 0400);
 MODULE_PARM_DESC(disable_irq, "disable interrupts: generate hard-lockups");

 static bool disable_softirq;
 module_param(disable_softirq, bool, 0400);
 MODULE_PARM_DESC(disable_softirq, "disable bottom-half irq handlers");

 static bool disable_preempt;
 module_param(disable_preempt, bool, 0400);
 MODULE_PARM_DESC(disable_preempt, "disable preemption: generate soft-lockups");

 static bool lock_rcu;
 module_param(lock_rcu, bool, 0400);
 MODULE_PARM_DESC(lock_rcu, "grab rcu_read_lock: generate rcu stalls");

 static bool lock_mmap_sem;
 module_param(lock_mmap_sem, bool, 0400);
 MODULE_PARM_DESC(lock_mmap_sem, "lock mm->mmap_lock: block procfs interfaces");

 static unsigned long lock_rwsem_ptr;
 module_param_unsafe(lock_rwsem_ptr, ulong, 0400);
 MODULE_PARM_DESC(lock_rwsem_ptr, "lock rw_semaphore at address");

 static unsigned long lock_mutex_ptr;
 module_param_unsafe(lock_mutex_ptr, ulong, 0400);
 MODULE_PARM_DESC(lock_mutex_ptr, "lock mutex at address");

 static unsigned long lock_spinlock_ptr;
 module_param_unsafe(lock_spinlock_ptr, ulong, 0400);
 MODULE_PARM_DESC(lock_spinlock_ptr, "lock spinlock at address");

 static unsigned long lock_rwlock_ptr;
 module_param_unsafe(lock_rwlock_ptr, ulong, 0400);
 MODULE_PARM_DESC(lock_rwlock_ptr, "lock rwlock at address");

 static unsigned int alloc_pages_nr;
 module_param_unsafe(alloc_pages_nr, uint, 0600);
 MODULE_PARM_DESC(alloc_pages_nr, "allocate and free pages under locks");

 static unsigned int alloc_pages_order;
 module_param(alloc_pages_order, uint, 0400);
 MODULE_PARM_DESC(alloc_pages_order, "page order to allocate");

 static gfp_t alloc_pages_gfp = GFP_KERNEL;
 module_param_unsafe(alloc_pages_gfp, uint, 0400);
 MODULE_PARM_DESC(alloc_pages_gfp, "allocate pages with this gfp_mask, default GFP_KERNEL");

 static bool alloc_pages_atomic;
 module_param(alloc_pages_atomic, bool, 0400);
 MODULE_PARM_DESC(alloc_pages_atomic, "allocate pages with GFP_ATOMIC");

 static bool reallocate_pages;
 module_param(reallocate_pages, bool, 0400);
 MODULE_PARM_DESC(reallocate_pages, "free and allocate pages between iterations");

 struct file *test_file;
 static struct inode *test_inode;
 static char test_file_path[256];
 module_param_string(file_path, test_file_path, sizeof(test_file_path), 0400);
 MODULE_PARM_DESC(file_path, "file path to test");

 static bool test_lock_inode;
 module_param_named(lock_inode, test_lock_inode, bool, 0400);
 MODULE_PARM_DESC(lock_inode, "lock file -> inode -> i_rwsem");

 static bool test_lock_mapping;
 module_param_named(lock_mapping, test_lock_mapping, bool, 0400);
 MODULE_PARM_DESC(lock_mapping, "lock file -> mapping -> i_mmap_rwsem");

 static bool test_lock_sb_umount;
 module_param_named(lock_sb_umount, test_lock_sb_umount, bool, 0400);
 MODULE_PARM_DESC(lock_sb_umount, "lock file -> sb -> s_umount");

 static atomic_t alloc_pages_failed = ATOMIC_INIT(0);

 static atomic64_t max_lock_wait = ATOMIC64_INIT(0);

 static struct task_struct *main_task;
 static int master_cpu;

 static void test_lock(bool master, bool verbose)
 {
 	u64 wait_start;

 	if (measure_lock_wait)
 		wait_start = local_clock();

 	if (lock_mutex_ptr && master) {
 		if (verbose)
 			pr_notice("lock mutex %ps\n", (void *)lock_mutex_ptr);
 		mutex_lock((struct mutex *)lock_mutex_ptr);
 	}

 	if (lock_rwsem_ptr && master) {
 		if (verbose)
 			pr_notice("lock rw_semaphore %ps\n",
 				  (void *)lock_rwsem_ptr);
 		if (lock_read)
 			down_read((struct rw_semaphore *)lock_rwsem_ptr);
 		else
 			down_write((struct rw_semaphore *)lock_rwsem_ptr);
 	}

 	if (lock_mmap_sem && master) {
 		if (verbose)
 			pr_notice("lock mmap_lock pid=%d\n", main_task->pid);
 		if (lock_read)
 			mmap_read_lock(main_task->mm);
 		else
 			mmap_write_lock(main_task->mm);
 	}

 	if (test_disable_irq)
 		local_irq_disable();

 	if (disable_softirq)
 		local_bh_disable();

 	if (disable_preempt)
 		preempt_disable();

 	if (lock_rcu)
 		rcu_read_lock();

 	if (lock_spinlock_ptr && master) {
 		if (verbose)
 			pr_notice("lock spinlock %ps\n",
 				  (void *)lock_spinlock_ptr);
 		spin_lock((spinlock_t *)lock_spinlock_ptr);
 	}

 	if (lock_rwlock_ptr && master) {
 		if (verbose)
 			pr_notice("lock rwlock %ps\n",
 				  (void *)lock_rwlock_ptr);
 		if (lock_read)
 			read_lock((rwlock_t *)lock_rwlock_ptr);
 		else
 			write_lock((rwlock_t *)lock_rwlock_ptr);
 	}

 	if (measure_lock_wait) {
 		s64 cur_wait = local_clock() - wait_start;
 		s64 max_wait = atomic64_read(&max_lock_wait);

 		do {
 			if (cur_wait < max_wait)
 				break;
 			max_wait = atomic64_cmpxchg(&max_lock_wait,
 						    max_wait, cur_wait);
 		} while (max_wait != cur_wait);

 		if (cur_wait > lock_wait_threshold)
 			pr_notice_ratelimited("lock wait %lld ns\n", cur_wait);
 	}
 }

 static void test_unlock(bool master, bool verbose)
 {
 	if (lock_rwlock_ptr && master) {
 		if (lock_read)
 			read_unlock((rwlock_t *)lock_rwlock_ptr);
 		else
 			write_unlock((rwlock_t *)lock_rwlock_ptr);
 		if (verbose)
 			pr_notice("unlock rwlock %ps\n",
 				  (void *)lock_rwlock_ptr);
 	}

 	if (lock_spinlock_ptr && master) {
 		spin_unlock((spinlock_t *)lock_spinlock_ptr);
 		if (verbose)
 			pr_notice("unlock spinlock %ps\n",
 				  (void *)lock_spinlock_ptr);
 	}

 	if (lock_rcu)
 		rcu_read_unlock();

 	if (disable_preempt)
 		preempt_enable();

 	if (disable_softirq)
 		local_bh_enable();

 	if (test_disable_irq)
 		local_irq_enable();

 	if (lock_mmap_sem && master) {
 		if (lock_read)
 			mmap_read_unlock(main_task->mm);
 		else
 			mmap_write_unlock(main_task->mm);
 		if (verbose)
 			pr_notice("unlock mmap_lock pid=%d\n", main_task->pid);
 	}

 	if (lock_rwsem_ptr && master) {
 		if (lock_read)
 			up_read((struct rw_semaphore *)lock_rwsem_ptr);
 		else
 			up_write((struct rw_semaphore *)lock_rwsem_ptr);
 		if (verbose)
 			pr_notice("unlock rw_semaphore %ps\n",
 				  (void *)lock_rwsem_ptr);
 	}

 	if (lock_mutex_ptr && master) {
 		mutex_unlock((struct mutex *)lock_mutex_ptr);
 		if (verbose)
 			pr_notice("unlock mutex %ps\n",
 				  (void *)lock_mutex_ptr);
 	}
 }

 static void test_alloc_pages(struct list_head *pages)
 {
 	struct page *page;
 	unsigned int i;

 	for (i = 0; i < alloc_pages_nr; i++) {
 		page = alloc_pages(alloc_pages_gfp, alloc_pages_order);
 		if (!page) {
 			atomic_inc(&alloc_pages_failed);
 			break;
 		}
 		list_add(&page->lru, pages);
 	}
 }

 static void test_free_pages(struct list_head *pages)
 {
 	struct page *page, *next;

 	list_for_each_entry_safe(page, next, pages, lru)
 		__free_pages(page, alloc_pages_order);
 	INIT_LIST_HEAD(pages);
 }

 static void test_wait(unsigned int secs, unsigned int nsecs)
 {
 	if (wait_state == TASK_RUNNING) {
 		if (secs)
 			mdelay(secs * MSEC_PER_SEC);
 		if (nsecs)
 			ndelay(nsecs);
 		return;
 	}

 	__set_current_state(wait_state);
 	if (use_hrtimer) {
 		ktime_t time;

 		time = ns_to_ktime((u64)secs * NSEC_PER_SEC + nsecs);
 		schedule_hrtimeout(&time, HRTIMER_MODE_REL);
 	} else {
 		schedule_timeout(secs * HZ + nsecs_to_jiffies(nsecs));
 	}
 }

 static void test_lockup(bool master)
 {
 	u64 lockup_start = local_clock();
 	unsigned int iter = 0;
 	LIST_HEAD(pages);

 	pr_notice("Start on CPU%d\n", raw_smp_processor_id());

 	test_lock(master, true);

 	test_alloc_pages(&pages);

 	while (iter++ < iterations && !signal_pending(main_task)) {

 		if (iowait)
 			current->in_iowait = 1;

 		test_wait(time_secs, time_nsecs);

 		if (iowait)
 			current->in_iowait = 0;

 		if (reallocate_pages)
 			test_free_pages(&pages);

 		if (reacquire_locks)
 			test_unlock(master, false);

 		if (touch_softlockup)
 			touch_softlockup_watchdog();

 		if (touch_hardlockup)
 			touch_nmi_watchdog();

 		if (call_cond_resched)
 			cond_resched();

 		test_wait(cooldown_secs, cooldown_nsecs);

 		if (reacquire_locks)
 			test_lock(master, false);

 		if (reallocate_pages)
 			test_alloc_pages(&pages);
 	}

 	pr_notice("Finish on CPU%d in %lld ns\n", raw_smp_processor_id(),
 		  local_clock() - lockup_start);

 	test_free_pages(&pages);

 	test_unlock(master, true);
 }

 static DEFINE_PER_CPU(struct work_struct, test_works);

 static void test_work_fn(struct work_struct *work)
 {
 	test_lockup(!lock_single ||
 		    work == per_cpu_ptr(&test_works, master_cpu));
 }

 static bool test_kernel_ptr(unsigned long addr, int size)
 {
 	void *ptr = (void *)addr;
 	char buf;

 	if (!addr)
 		return false;

 	/* should be at least readable kernel address */
 	if (access_ok(ptr, 1) ||
 	    access_ok(ptr + size - 1, 1) ||
 	    get_kernel_nofault(buf, ptr) ||
 	    get_kernel_nofault(buf, ptr + size - 1)) {
 		pr_err("invalid kernel ptr: %#lx\n", addr);
 		return true;
 	}

 	return false;
 }

 static bool __maybe_unused test_magic(unsigned long addr, int offset,
 				      unsigned int expected)
 {
 	void *ptr = (void *)addr + offset;
 	unsigned int magic = 0;

 	if (!addr)
 		return false;

 	if (get_kernel_nofault(magic, ptr) || magic != expected) {
 		pr_err("invalid magic at %#lx + %#x = %#x, expected %#x\n",
 		       addr, offset, magic, expected);
 		return true;
 	}

 	return false;
 }

 static int __init test_lockup_init(void)
 {
 	u64 test_start = local_clock();

 	main_task = current;

 	switch (state[0]) {
 	case 'S':
 		wait_state = TASK_INTERRUPTIBLE;
 		break;
 	case 'D':
 		wait_state = TASK_UNINTERRUPTIBLE;
 		break;
 	case 'K':
 		wait_state = TASK_KILLABLE;
 		break;
 	case 'R':
 		wait_state = TASK_RUNNING;
 		break;
 	default:
 		pr_err("unknown state=%s\n", state);
 		return -EINVAL;
 	}

 	if (alloc_pages_atomic)
 		alloc_pages_gfp = GFP_ATOMIC;

 	if (test_kernel_ptr(lock_spinlock_ptr, sizeof(spinlock_t)) ||
 	    test_kernel_ptr(lock_rwlock_ptr, sizeof(rwlock_t)) ||
 	    test_kernel_ptr(lock_mutex_ptr, sizeof(struct mutex)) ||
 	    test_kernel_ptr(lock_rwsem_ptr, sizeof(struct rw_semaphore)))
 		return -EINVAL;

 #ifdef CONFIG_DEBUG_SPINLOCK
 	if (test_magic(lock_spinlock_ptr,
 		       offsetof(spinlock_t, rlock.magic),
 		       SPINLOCK_MAGIC) ||
 	    test_magic(lock_rwlock_ptr,
 		       offsetof(rwlock_t, magic),
 		       RWLOCK_MAGIC) ||
 	    test_magic(lock_mutex_ptr,
 		       offsetof(struct mutex, wait_lock.rlock.magic),
 		       SPINLOCK_MAGIC) ||
 	    test_magic(lock_rwsem_ptr,
 		       offsetof(struct rw_semaphore, wait_lock.magic),
 		       SPINLOCK_MAGIC))
 		return -EINVAL;
 #endif

 	if ((wait_state != TASK_RUNNING ||
 	     (call_cond_resched && !reacquire_locks) ||
 	     (alloc_pages_nr && gfpflags_allow_blocking(alloc_pages_gfp))) &&
 	    (test_disable_irq || disable_softirq || disable_preempt ||
 	     lock_rcu || lock_spinlock_ptr || lock_rwlock_ptr)) {
 		pr_err("refuse to sleep in atomic context\n");
 		return -EINVAL;
 	}

 	if (lock_mmap_sem && !main_task->mm) {
 		pr_err("no mm to lock mmap_lock\n");
 		return -EINVAL;
 	}

 	if (test_file_path[0]) {
 		test_file = filp_open(test_file_path, O_RDONLY, 0);
 		if (IS_ERR(test_file)) {
 			pr_err("failed to open %s: %ld\n", test_file_path, PTR_ERR(test_file));
 			return PTR_ERR(test_file);
 		}
 		test_inode = file_inode(test_file);
 	} else if (test_lock_inode ||
 		   test_lock_mapping ||
 		   test_lock_sb_umount) {
 		pr_err("no file to lock\n");
 		return -EINVAL;
 	}

 	if (test_lock_inode && test_inode)
 		lock_rwsem_ptr = (unsigned long)&test_inode->i_rwsem;

 	if (test_lock_mapping && test_file && test_file->f_mapping)
 		lock_rwsem_ptr = (unsigned long)&test_file->f_mapping->i_mmap_rwsem;

 	if (test_lock_sb_umount && test_inode)
 		lock_rwsem_ptr = (unsigned long)&test_inode->i_sb->s_umount;

 	pr_notice("START pid=%d time=%u +%u ns cooldown=%u +%u ns iterations=%u state=%s %s%s%s%s%s%s%s%s%s%s%s\n",
 		  main_task->pid, time_secs, time_nsecs,
 		  cooldown_secs, cooldown_nsecs, iterations, state,
 		  all_cpus ? "all_cpus " : "",
 		  iowait ? "iowait " : "",
 		  test_disable_irq ? "disable_irq " : "",
 		  disable_softirq ? "disable_softirq " : "",
 		  disable_preempt ? "disable_preempt " : "",
 		  lock_rcu ? "lock_rcu " : "",
 		  lock_read ? "lock_read " : "",
 		  touch_softlockup ? "touch_softlockup " : "",
 		  touch_hardlockup ? "touch_hardlockup " : "",
 		  call_cond_resched ? "call_cond_resched " : "",
 		  reacquire_locks ? "reacquire_locks " : "");

 	if (alloc_pages_nr)
 		pr_notice("ALLOCATE PAGES nr=%u order=%u gfp=%pGg %s\n",
 			  alloc_pages_nr, alloc_pages_order, &alloc_pages_gfp,
 			  reallocate_pages ? "reallocate_pages " : "");

 	if (all_cpus) {
 		unsigned int cpu;

 		cpus_read_lock();

 		preempt_disable();
 		master_cpu = smp_processor_id();
 		for_each_online_cpu(cpu) {
 			INIT_WORK(per_cpu_ptr(&test_works, cpu), test_work_fn);
 			queue_work_on(cpu, system_highpri_wq,
 				      per_cpu_ptr(&test_works, cpu));
 		}
 		preempt_enable();

 		for_each_online_cpu(cpu)
 			flush_work(per_cpu_ptr(&test_works, cpu));

 		cpus_read_unlock();
 	} else {
 		test_lockup(true);
 	}

 	if (measure_lock_wait)
 		pr_notice("Maximum lock wait: %lld ns\n",
 			  atomic64_read(&max_lock_wait));

 	if (alloc_pages_nr)
 		pr_notice("Page allocation failed %u times\n",
 			  atomic_read(&alloc_pages_failed));

 	pr_notice("FINISH in %llu ns\n", local_clock() - test_start);

 	if (test_file)
 		fput(test_file);

 	if (signal_pending(main_task))
 		return -EINTR;

 	return -EAGAIN;
 }
 module_init(test_lockup_init);

 MODULE_LICENSE("GPL");
 MODULE_IMPORT_NS(VFS_internal_I_am_really_a_filesystem_and_am_NOT_a_driver);
 MODULE_AUTHOR("Konstantin Khlebnikov <khlebnikov@yandex-team.ru>");
 MODULE_DESCRIPTION("Test module to generate lockups");
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Test module to generate lockups
	*/
	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/delay.h>
	#include <linux/sched.h>
	#include <linux/sched/signal.h>
	#include <linux/sched/clock.h>
	#include <linux/cpu.h>
	#include <linux/nmi.h>
	#include <linux/mm.h>
	#include <linux/uaccess.h>
	#include <linux/file.h>

	static unsigned int time_secs;
	module_param(time_secs, uint, 0600);
	MODULE_PARM_DESC(time_secs, "lockup time in seconds, default 0");

	static unsigned int time_nsecs;
	module_param(time_nsecs, uint, 0600);
	MODULE_PARM_DESC(time_nsecs, "nanoseconds part of lockup time, default 0");

	static unsigned int cooldown_secs;
	module_param(cooldown_secs, uint, 0600);
	MODULE_PARM_DESC(cooldown_secs, "cooldown time between iterations in seconds, default 0");

	static unsigned int cooldown_nsecs;
	module_param(cooldown_nsecs, uint, 0600);
	MODULE_PARM_DESC(cooldown_nsecs, "nanoseconds part of cooldown, default 0");

	static unsigned int iterations = 1;
	module_param(iterations, uint, 0600);
	MODULE_PARM_DESC(iterations, "lockup iterations, default 1");

	static bool all_cpus;
	module_param(all_cpus, bool, 0400);
	MODULE_PARM_DESC(all_cpus, "trigger lockup at all cpus at once");

	static int wait_state;
	static char *state = "R";
	module_param(state, charp, 0400);
	MODULE_PARM_DESC(state, "wait in 'R' running (default), 'D' uninterruptible, 'K' killable, 'S' interruptible state");

	static bool use_hrtimer;
	module_param(use_hrtimer, bool, 0400);
	MODULE_PARM_DESC(use_hrtimer, "use high-resolution timer for sleeping");

	static bool iowait;
	module_param(iowait, bool, 0400);
	MODULE_PARM_DESC(iowait, "account sleep time as iowait");

	static bool lock_read;
	module_param(lock_read, bool, 0400);
	MODULE_PARM_DESC(lock_read, "lock read-write locks for read");

	static bool lock_single;
	module_param(lock_single, bool, 0400);
	MODULE_PARM_DESC(lock_single, "acquire locks only at one cpu");

	static bool reacquire_locks;
	module_param(reacquire_locks, bool, 0400);
	MODULE_PARM_DESC(reacquire_locks, "release and reacquire locks/irq/preempt between iterations");

	static bool touch_softlockup;
	module_param(touch_softlockup, bool, 0600);
	MODULE_PARM_DESC(touch_softlockup, "touch soft-lockup watchdog between iterations");

	static bool touch_hardlockup;
	module_param(touch_hardlockup, bool, 0600);
	MODULE_PARM_DESC(touch_hardlockup, "touch hard-lockup watchdog between iterations");

	static bool call_cond_resched;
	module_param(call_cond_resched, bool, 0600);
	MODULE_PARM_DESC(call_cond_resched, "call cond_resched() between iterations");

	static bool measure_lock_wait;
	module_param(measure_lock_wait, bool, 0400);
	MODULE_PARM_DESC(measure_lock_wait, "measure lock wait time");

	static unsigned long lock_wait_threshold = ULONG_MAX;
	module_param(lock_wait_threshold, ulong, 0400);
	MODULE_PARM_DESC(lock_wait_threshold, "print lock wait time longer than this in nanoseconds, default off");

	static bool test_disable_irq;
	module_param_named(disable_irq, test_disable_irq, bool, 0400);
	MODULE_PARM_DESC(disable_irq, "disable interrupts: generate hard-lockups");

	static bool disable_softirq;
	module_param(disable_softirq, bool, 0400);
	MODULE_PARM_DESC(disable_softirq, "disable bottom-half irq handlers");

	static bool disable_preempt;
	module_param(disable_preempt, bool, 0400);
	MODULE_PARM_DESC(disable_preempt, "disable preemption: generate soft-lockups");

	static bool lock_rcu;
	module_param(lock_rcu, bool, 0400);
	MODULE_PARM_DESC(lock_rcu, "grab rcu_read_lock: generate rcu stalls");

	static bool lock_mmap_sem;
	module_param(lock_mmap_sem, bool, 0400);
	MODULE_PARM_DESC(lock_mmap_sem, "lock mm->mmap_lock: block procfs interfaces");

	static unsigned long lock_rwsem_ptr;
	module_param_unsafe(lock_rwsem_ptr, ulong, 0400);
	MODULE_PARM_DESC(lock_rwsem_ptr, "lock rw_semaphore at address");

	static unsigned long lock_mutex_ptr;
	module_param_unsafe(lock_mutex_ptr, ulong, 0400);
	MODULE_PARM_DESC(lock_mutex_ptr, "lock mutex at address");

	static unsigned long lock_spinlock_ptr;
	module_param_unsafe(lock_spinlock_ptr, ulong, 0400);
	MODULE_PARM_DESC(lock_spinlock_ptr, "lock spinlock at address");

	static unsigned long lock_rwlock_ptr;
	module_param_unsafe(lock_rwlock_ptr, ulong, 0400);
	MODULE_PARM_DESC(lock_rwlock_ptr, "lock rwlock at address");

	static unsigned int alloc_pages_nr;
	module_param_unsafe(alloc_pages_nr, uint, 0600);
	MODULE_PARM_DESC(alloc_pages_nr, "allocate and free pages under locks");

	static unsigned int alloc_pages_order;
	module_param(alloc_pages_order, uint, 0400);
	MODULE_PARM_DESC(alloc_pages_order, "page order to allocate");

	static gfp_t alloc_pages_gfp = GFP_KERNEL;
	module_param_unsafe(alloc_pages_gfp, uint, 0400);
	MODULE_PARM_DESC(alloc_pages_gfp, "allocate pages with this gfp_mask, default GFP_KERNEL");

	static bool alloc_pages_atomic;
	module_param(alloc_pages_atomic, bool, 0400);
	MODULE_PARM_DESC(alloc_pages_atomic, "allocate pages with GFP_ATOMIC");

	static bool reallocate_pages;
	module_param(reallocate_pages, bool, 0400);
	MODULE_PARM_DESC(reallocate_pages, "free and allocate pages between iterations");

	struct file *test_file;
	static struct inode *test_inode;
	static char test_file_path[256];
	module_param_string(file_path, test_file_path, sizeof(test_file_path), 0400);
	MODULE_PARM_DESC(file_path, "file path to test");

	static bool test_lock_inode;
	module_param_named(lock_inode, test_lock_inode, bool, 0400);
	MODULE_PARM_DESC(lock_inode, "lock file -> inode -> i_rwsem");

	static bool test_lock_mapping;
	module_param_named(lock_mapping, test_lock_mapping, bool, 0400);
	MODULE_PARM_DESC(lock_mapping, "lock file -> mapping -> i_mmap_rwsem");

	static bool test_lock_sb_umount;
	module_param_named(lock_sb_umount, test_lock_sb_umount, bool, 0400);
	MODULE_PARM_DESC(lock_sb_umount, "lock file -> sb -> s_umount");

	static atomic_t alloc_pages_failed = ATOMIC_INIT(0);

	static atomic64_t max_lock_wait = ATOMIC64_INIT(0);

	static struct task_struct *main_task;
	static int master_cpu;

	static void test_lock(bool master, bool verbose)
	{
	u64 wait_start;

	if (measure_lock_wait)
	wait_start = local_clock();

	if (lock_mutex_ptr && master) {
	if (verbose)
	pr_notice("lock mutex %ps\n", (void *)lock_mutex_ptr);
	mutex_lock((struct mutex *)lock_mutex_ptr);
	}

	if (lock_rwsem_ptr && master) {
	if (verbose)
	pr_notice("lock rw_semaphore %ps\n",
	(void *)lock_rwsem_ptr);
	if (lock_read)
	down_read((struct rw_semaphore *)lock_rwsem_ptr);
	else
	down_write((struct rw_semaphore *)lock_rwsem_ptr);
	}

	if (lock_mmap_sem && master) {
	if (verbose)
	pr_notice("lock mmap_lock pid=%d\n", main_task->pid);
	if (lock_read)
	mmap_read_lock(main_task->mm);
	else
	mmap_write_lock(main_task->mm);
	}

	if (test_disable_irq)
	local_irq_disable();

	if (disable_softirq)
	local_bh_disable();

	if (disable_preempt)
	preempt_disable();

	if (lock_rcu)
	rcu_read_lock();

	if (lock_spinlock_ptr && master) {
	if (verbose)
	pr_notice("lock spinlock %ps\n",
	(void *)lock_spinlock_ptr);
	spin_lock((spinlock_t *)lock_spinlock_ptr);
	}

	if (lock_rwlock_ptr && master) {
	if (verbose)
	pr_notice("lock rwlock %ps\n",
	(void *)lock_rwlock_ptr);
	if (lock_read)
	read_lock((rwlock_t *)lock_rwlock_ptr);
	else
	write_lock((rwlock_t *)lock_rwlock_ptr);
	}

	if (measure_lock_wait) {
	s64 cur_wait = local_clock() - wait_start;
	s64 max_wait = atomic64_read(&max_lock_wait);

	do {
	if (cur_wait < max_wait)
	break;
	max_wait = atomic64_cmpxchg(&max_lock_wait,
	max_wait, cur_wait);
	} while (max_wait != cur_wait);

	if (cur_wait > lock_wait_threshold)
	pr_notice_ratelimited("lock wait %lld ns\n", cur_wait);
	}
	}

	static void test_unlock(bool master, bool verbose)
	{
	if (lock_rwlock_ptr && master) {
	if (lock_read)
	read_unlock((rwlock_t *)lock_rwlock_ptr);
	else
	write_unlock((rwlock_t *)lock_rwlock_ptr);
	if (verbose)
	pr_notice("unlock rwlock %ps\n",
	(void *)lock_rwlock_ptr);
	}

	if (lock_spinlock_ptr && master) {
	spin_unlock((spinlock_t *)lock_spinlock_ptr);
	if (verbose)
	pr_notice("unlock spinlock %ps\n",
	(void *)lock_spinlock_ptr);
	}

	if (lock_rcu)
	rcu_read_unlock();

	if (disable_preempt)
	preempt_enable();

	if (disable_softirq)
	local_bh_enable();

	if (test_disable_irq)
	local_irq_enable();

	if (lock_mmap_sem && master) {
	if (lock_read)
	mmap_read_unlock(main_task->mm);
	else
	mmap_write_unlock(main_task->mm);
	if (verbose)
	pr_notice("unlock mmap_lock pid=%d\n", main_task->pid);
	}

	if (lock_rwsem_ptr && master) {
	if (lock_read)
	up_read((struct rw_semaphore *)lock_rwsem_ptr);
	else
	up_write((struct rw_semaphore *)lock_rwsem_ptr);
	if (verbose)
	pr_notice("unlock rw_semaphore %ps\n",
	(void *)lock_rwsem_ptr);
	}

	if (lock_mutex_ptr && master) {
	mutex_unlock((struct mutex *)lock_mutex_ptr);
	if (verbose)
	pr_notice("unlock mutex %ps\n",
	(void *)lock_mutex_ptr);
	}
	}

	static void test_alloc_pages(struct list_head *pages)
	{
	struct page *page;
	unsigned int i;

	for (i = 0; i < alloc_pages_nr; i++) {
	page = alloc_pages(alloc_pages_gfp, alloc_pages_order);
	if (!page) {
	atomic_inc(&alloc_pages_failed);
	break;
	}
	list_add(&page->lru, pages);
	}
	}

	static void test_free_pages(struct list_head *pages)
	{
	struct page page, next;

	list_for_each_entry_safe(page, next, pages, lru)
	__free_pages(page, alloc_pages_order);
	INIT_LIST_HEAD(pages);
	}

	static void test_wait(unsigned int secs, unsigned int nsecs)
	{
	if (wait_state == TASK_RUNNING) {
	if (secs)
	mdelay(secs * MSEC_PER_SEC);
	if (nsecs)
	ndelay(nsecs);
	return;
	}

	__set_current_state(wait_state);
	if (use_hrtimer) {
	ktime_t time;

	time = ns_to_ktime((u64)secs * NSEC_PER_SEC + nsecs);
	schedule_hrtimeout(&time, HRTIMER_MODE_REL);
	} else {
	schedule_timeout(secs * HZ + nsecs_to_jiffies(nsecs));
	}
	}

	static void test_lockup(bool master)
	{
	u64 lockup_start = local_clock();
	unsigned int iter = 0;
	LIST_HEAD(pages);

	pr_notice("Start on CPU%d\n", raw_smp_processor_id());

	test_lock(master, true);

	test_alloc_pages(&pages);

	while (iter++ < iterations && !signal_pending(main_task)) {

	if (iowait)
	current->in_iowait = 1;

	test_wait(time_secs, time_nsecs);

	if (iowait)
	current->in_iowait = 0;

	if (reallocate_pages)
	test_free_pages(&pages);

	if (reacquire_locks)
	test_unlock(master, false);

	if (touch_softlockup)
	touch_softlockup_watchdog();

	if (touch_hardlockup)
	touch_nmi_watchdog();

	if (call_cond_resched)
	cond_resched();

	test_wait(cooldown_secs, cooldown_nsecs);

	if (reacquire_locks)
	test_lock(master, false);

	if (reallocate_pages)
	test_alloc_pages(&pages);
	}

	pr_notice("Finish on CPU%d in %lld ns\n", raw_smp_processor_id(),
	local_clock() - lockup_start);

	test_free_pages(&pages);

	test_unlock(master, true);
	}

	static DEFINE_PER_CPU(struct work_struct, test_works);

	static void test_work_fn(struct work_struct *work)
	{
	test_lockup(!lock_single \|\|
	work == per_cpu_ptr(&test_works, master_cpu));
	}

	static bool test_kernel_ptr(unsigned long addr, int size)
	{
	void ptr = (void )addr;
	char buf;

	if (!addr)
	return false;

	/* should be at least readable kernel address */
	if (access_ok(ptr, 1) \|\|
	access_ok(ptr + size - 1, 1) \|\|
	get_kernel_nofault(buf, ptr) \|\|
	get_kernel_nofault(buf, ptr + size - 1)) {
	pr_err("invalid kernel ptr: %#lx\n", addr);
	return true;
	}

	return false;
	}

	static bool __maybe_unused test_magic(unsigned long addr, int offset,
	unsigned int expected)
	{
	void ptr = (void )addr + offset;
	unsigned int magic = 0;

	if (!addr)
	return false;

	if (get_kernel_nofault(magic, ptr) \|\| magic != expected) {
	pr_err("invalid magic at %#lx + %#x = %#x, expected %#x\n",
	addr, offset, magic, expected);
	return true;
	}

	return false;
	}

	static int __init test_lockup_init(void)
	{
	u64 test_start = local_clock();

	main_task = current;

	switch (state[0]) {
	case 'S':
	wait_state = TASK_INTERRUPTIBLE;
	break;
	case 'D':
	wait_state = TASK_UNINTERRUPTIBLE;
	break;
	case 'K':
	wait_state = TASK_KILLABLE;
	break;
	case 'R':
	wait_state = TASK_RUNNING;
	break;
	default:
	pr_err("unknown state=%s\n", state);
	return -EINVAL;
	}

	if (alloc_pages_atomic)
	alloc_pages_gfp = GFP_ATOMIC;

	if (test_kernel_ptr(lock_spinlock_ptr, sizeof(spinlock_t)) \|\|
	test_kernel_ptr(lock_rwlock_ptr, sizeof(rwlock_t)) \|\|
	test_kernel_ptr(lock_mutex_ptr, sizeof(struct mutex)) \|\|
	test_kernel_ptr(lock_rwsem_ptr, sizeof(struct rw_semaphore)))
	return -EINVAL;

	#ifdef CONFIG_DEBUG_SPINLOCK
	if (test_magic(lock_spinlock_ptr,
	offsetof(spinlock_t, rlock.magic),
	SPINLOCK_MAGIC) \|\|
	test_magic(lock_rwlock_ptr,
	offsetof(rwlock_t, magic),
	RWLOCK_MAGIC) \|\|
	test_magic(lock_mutex_ptr,
	offsetof(struct mutex, wait_lock.rlock.magic),
	SPINLOCK_MAGIC) \|\|
	test_magic(lock_rwsem_ptr,
	offsetof(struct rw_semaphore, wait_lock.magic),
	SPINLOCK_MAGIC))
	return -EINVAL;
	#endif

	if ((wait_state != TASK_RUNNING \|\|
	(call_cond_resched && !reacquire_locks) \|\|
	(alloc_pages_nr && gfpflags_allow_blocking(alloc_pages_gfp))) &&
	(test_disable_irq \|\| disable_softirq \|\| disable_preempt \|\|
	lock_rcu \|\| lock_spinlock_ptr \|\| lock_rwlock_ptr)) {
	pr_err("refuse to sleep in atomic context\n");
	return -EINVAL;
	}

	if (lock_mmap_sem && !main_task->mm) {
	pr_err("no mm to lock mmap_lock\n");
	return -EINVAL;
	}

	if (test_file_path[0]) {
	test_file = filp_open(test_file_path, O_RDONLY, 0);
	if (IS_ERR(test_file)) {
	pr_err("failed to open %s: %ld\n", test_file_path, PTR_ERR(test_file));
	return PTR_ERR(test_file);
	}
	test_inode = file_inode(test_file);
	} else if (test_lock_inode \|\|
	test_lock_mapping \|\|
	test_lock_sb_umount) {
	pr_err("no file to lock\n");
	return -EINVAL;
	}

	if (test_lock_inode && test_inode)
	lock_rwsem_ptr = (unsigned long)&test_inode->i_rwsem;

	if (test_lock_mapping && test_file && test_file->f_mapping)
	lock_rwsem_ptr = (unsigned long)&test_file->f_mapping->i_mmap_rwsem;

	if (test_lock_sb_umount && test_inode)
	lock_rwsem_ptr = (unsigned long)&test_inode->i_sb->s_umount;

	pr_notice("START pid=%d time=%u +%u ns cooldown=%u +%u ns iterations=%u state=%s %s%s%s%s%s%s%s%s%s%s%s\n",
	main_task->pid, time_secs, time_nsecs,
	cooldown_secs, cooldown_nsecs, iterations, state,
	all_cpus ? "all_cpus " : "",
	iowait ? "iowait " : "",
	test_disable_irq ? "disable_irq " : "",
	disable_softirq ? "disable_softirq " : "",
	disable_preempt ? "disable_preempt " : "",
	lock_rcu ? "lock_rcu " : "",
	lock_read ? "lock_read " : "",
	touch_softlockup ? "touch_softlockup " : "",
	touch_hardlockup ? "touch_hardlockup " : "",
	call_cond_resched ? "call_cond_resched " : "",
	reacquire_locks ? "reacquire_locks " : "");

	if (alloc_pages_nr)
	pr_notice("ALLOCATE PAGES nr=%u order=%u gfp=%pGg %s\n",
	alloc_pages_nr, alloc_pages_order, &alloc_pages_gfp,
	reallocate_pages ? "reallocate_pages " : "");

	if (all_cpus) {
	unsigned int cpu;

	cpus_read_lock();

	preempt_disable();
	master_cpu = smp_processor_id();
	for_each_online_cpu(cpu) {
	INIT_WORK(per_cpu_ptr(&test_works, cpu), test_work_fn);
	queue_work_on(cpu, system_highpri_wq,
	per_cpu_ptr(&test_works, cpu));
	}
	preempt_enable();

	for_each_online_cpu(cpu)
	flush_work(per_cpu_ptr(&test_works, cpu));

	cpus_read_unlock();
	} else {
	test_lockup(true);
	}

	if (measure_lock_wait)
	pr_notice("Maximum lock wait: %lld ns\n",
	atomic64_read(&max_lock_wait));

	if (alloc_pages_nr)
	pr_notice("Page allocation failed %u times\n",
	atomic_read(&alloc_pages_failed));

	pr_notice("FINISH in %llu ns\n", local_clock() - test_start);

	if (test_file)
	fput(test_file);

	if (signal_pending(main_task))
	return -EINTR;

	return -EAGAIN;
	}
	module_init(test_lockup_init);

	MODULE_LICENSE("GPL");
	MODULE_IMPORT_NS(VFS_internal_I_am_really_a_filesystem_and_am_NOT_a_driver);
	MODULE_AUTHOR("Konstantin Khlebnikov <khlebnikov@yandex-team.ru>");
	MODULE_DESCRIPTION("Test module to generate lockups");