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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0+
 /*
  * Module-based torture test facility for locking
  *
  * Copyright (C) IBM Corporation, 2014
  *
  * Authors: Paul E. McKenney <paulmck@linux.ibm.com>
  *          Davidlohr Bueso <dave@stgolabs.net>
  *  Based on kernel/rcu/torture.c.
  */
 
 #define pr_fmt(fmt) fmt
 
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/kthread.h>
 #include <linux/sched/rt.h>
 #include <linux/spinlock.h>
 #include <linux/mutex.h>
 #include <linux/rwsem.h>
 #include <linux/smp.h>
 #include <linux/interrupt.h>
 #include <linux/sched.h>
 #include <uapi/linux/sched/types.h>
 #include <linux/rtmutex.h>
 #include <linux/atomic.h>
 #include <linux/moduleparam.h>
 #include <linux/delay.h>
 #include <linux/slab.h>
 #include <linux/torture.h>
 #include <linux/reboot.h>
 
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.ibm.com>");
 
 torture_param(int, nwriters_stress, -1,
          "Number of write-locking stress-test threads");
 torture_param(int, nreaders_stress, -1,
          "Number of read-locking stress-test threads");
 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, shuffle_interval, 3,
          "Number of jiffies between shuffles, 0=disable");
 torture_param(int, shutdown_secs, 0, "Shutdown time (j), <= zero to disable.");
 torture_param(int, stat_interval, 60,
          "Number of seconds between stats printk()s");
 torture_param(int, stutter, 5, "Number of jiffies to run/halt test, 0=disable");
 torture_param(int, verbose, 1,
          "Enable verbose debugging printk()s");
 
 static char *torture_type = "spin_lock";
 module_param(torture_type, charp, 0444);
 MODULE_PARM_DESC(torture_type,
          "Type of lock to torture (spin_lock, spin_lock_irq, mutex_lock, ...)");
 
 static struct task_struct *stats_task;
 static struct task_struct **writer_tasks;
 static struct task_struct **reader_tasks;
 
 static bool lock_is_write_held;
 static atomic_t lock_is_read_held;
 static unsigned long last_lock_release;
 
 struct lock_stress_stats {
     long n_lock_fail;
     long n_lock_acquired;
 };
 
 /* Forward reference. */
 static void lock_torture_cleanup(void);
 
 /*
  * Operations vector for selecting different types of tests.
  */
 struct lock_torture_ops {
     void (*init)(void);
     void (*exit)(void);
     int (*writelock)(int tid);
     void (*write_delay)(struct torture_random_state *trsp);
     void (*task_boost)(struct torture_random_state *trsp);
     void (*writeunlock)(int tid);
     int (*readlock)(int tid);
     void (*read_delay)(struct torture_random_state *trsp);
     void (*readunlock)(int tid);
 
     unsigned long flags; /* for irq spinlocks */
     const char *name;
 };
 
 struct lock_torture_cxt {
     int nrealwriters_stress;
     int nrealreaders_stress;
     bool debug_lock;
     bool init_called;
     atomic_t n_lock_torture_errors;
     struct lock_torture_ops *cur_ops;
     struct lock_stress_stats *lwsa; /* writer statistics */
     struct lock_stress_stats *lrsa; /* reader statistics */
 };
 static struct lock_torture_cxt cxt = { 0, 0, false, false,
                        ATOMIC_INIT(0),
                        NULL, NULL};
 /*
  * Definitions for lock torture testing.
  */
 
 static int torture_lock_busted_write_lock(int tid __maybe_unused)
 {
     return 0;  /* BUGGY, do not use in real life!!! */
 }
 
 static void torture_lock_busted_write_delay(struct torture_random_state *trsp)
 {
     const unsigned long longdelay_ms = 100;
 
     /* We want a long delay occasionally to force massive contention.  */
     if (!(torture_random(trsp) %
           (cxt.nrealwriters_stress * 2000 * longdelay_ms)))
         mdelay(longdelay_ms);
     if (!(torture_random(trsp) % (cxt.nrealwriters_stress * 20000)))
         torture_preempt_schedule();  /* Allow test to be preempted. */
 }
 
 static void torture_lock_busted_write_unlock(int tid __maybe_unused)
 {
       /* BUGGY, do not use in real life!!! */
 }
 
 static void torture_boost_dummy(struct torture_random_state *trsp)
 {
     /* Only rtmutexes care about priority */
 }
 
 static struct lock_torture_ops lock_busted_ops = {
     .writelock  = torture_lock_busted_write_lock,
     .write_delay    = torture_lock_busted_write_delay,
     .task_boost     = torture_boost_dummy,
     .writeunlock    = torture_lock_busted_write_unlock,
     .readlock       = NULL,
     .read_delay     = NULL,
     .readunlock     = NULL,
     .name       = "lock_busted"
 };
 
 static DEFINE_SPINLOCK(torture_spinlock);
 
 static int torture_spin_lock_write_lock(int tid __maybe_unused)
 __acquires(torture_spinlock)
 {
     spin_lock(&torture_spinlock);
     return 0;
 }
 
 static void torture_spin_lock_write_delay(struct torture_random_state *trsp)
 {
     const unsigned long shortdelay_us = 2;
     const unsigned long longdelay_ms = 100;
 
     /* We want a short delay mostly to emulate likely code, and
      * we want a long delay occasionally to force massive contention.
      */
     if (!(torture_random(trsp) %
           (cxt.nrealwriters_stress * 2000 * longdelay_ms)))
         mdelay(longdelay_ms);
     if (!(torture_random(trsp) %
           (cxt.nrealwriters_stress * 2 * shortdelay_us)))
         udelay(shortdelay_us);
     if (!(torture_random(trsp) % (cxt.nrealwriters_stress * 20000)))
         torture_preempt_schedule();  /* Allow test to be preempted. */
 }
 
 static void torture_spin_lock_write_unlock(int tid __maybe_unused)
 __releases(torture_spinlock)
 {
     spin_unlock(&torture_spinlock);
 }
 
 static struct lock_torture_ops spin_lock_ops = {
     .writelock  = torture_spin_lock_write_lock,
     .write_delay    = torture_spin_lock_write_delay,
     .task_boost     = torture_boost_dummy,
     .writeunlock    = torture_spin_lock_write_unlock,
     .readlock       = NULL,
     .read_delay     = NULL,
     .readunlock     = NULL,
     .name       = "spin_lock"
 };
 
 static int torture_spin_lock_write_lock_irq(int tid __maybe_unused)
 __acquires(torture_spinlock)
 {
     unsigned long flags;
 
     spin_lock_irqsave(&torture_spinlock, flags);
     cxt.cur_ops->flags = flags;
     return 0;
 }
 
 static void torture_lock_spin_write_unlock_irq(int tid __maybe_unused)
 __releases(torture_spinlock)
 {
     spin_unlock_irqrestore(&torture_spinlock, cxt.cur_ops->flags);
 }
 
 static struct lock_torture_ops spin_lock_irq_ops = {
     .writelock  = torture_spin_lock_write_lock_irq,
     .write_delay    = torture_spin_lock_write_delay,
     .task_boost     = torture_boost_dummy,
     .writeunlock    = torture_lock_spin_write_unlock_irq,
     .readlock       = NULL,
     .read_delay     = NULL,
     .readunlock     = NULL,
     .name       = "spin_lock_irq"
 };
 
 static DEFINE_RWLOCK(torture_rwlock);
 
 static int torture_rwlock_write_lock(int tid __maybe_unused)
 __acquires(torture_rwlock)
 {
     write_lock(&torture_rwlock);
     return 0;
 }
 
 static void torture_rwlock_write_delay(struct torture_random_state *trsp)
 {
     const unsigned long shortdelay_us = 2;
     const unsigned long longdelay_ms = 100;
 
     /* We want a short delay mostly to emulate likely code, and
      * we want a long delay occasionally to force massive contention.
      */
     if (!(torture_random(trsp) %
           (cxt.nrealwriters_stress * 2000 * longdelay_ms)))
         mdelay(longdelay_ms);
     else
         udelay(shortdelay_us);
 }
 
 static void torture_rwlock_write_unlock(int tid __maybe_unused)
 __releases(torture_rwlock)
 {
     write_unlock(&torture_rwlock);
 }
 
 static int torture_rwlock_read_lock(int tid __maybe_unused)
 __acquires(torture_rwlock)
 {
     read_lock(&torture_rwlock);
     return 0;
 }
 
 static void torture_rwlock_read_delay(struct torture_random_state *trsp)
 {
     const unsigned long shortdelay_us = 10;
     const unsigned long longdelay_ms = 100;
 
     /* We want a short delay mostly to emulate likely code, and
      * we want a long delay occasionally to force massive contention.
      */
     if (!(torture_random(trsp) %
           (cxt.nrealreaders_stress * 2000 * longdelay_ms)))
         mdelay(longdelay_ms);
     else
         udelay(shortdelay_us);
 }
 
 static void torture_rwlock_read_unlock(int tid __maybe_unused)
 __releases(torture_rwlock)
 {
     read_unlock(&torture_rwlock);
 }
 
 static struct lock_torture_ops rw_lock_ops = {
     .writelock  = torture_rwlock_write_lock,
     .write_delay    = torture_rwlock_write_delay,
     .task_boost     = torture_boost_dummy,
     .writeunlock    = torture_rwlock_write_unlock,
     .readlock       = torture_rwlock_read_lock,
     .read_delay     = torture_rwlock_read_delay,
     .readunlock     = torture_rwlock_read_unlock,
     .name       = "rw_lock"
 };
 
 static int torture_rwlock_write_lock_irq(int tid __maybe_unused)
 __acquires(torture_rwlock)
 {
     unsigned long flags;
 
     write_lock_irqsave(&torture_rwlock, flags);
     cxt.cur_ops->flags = flags;
     return 0;
 }
 
 static void torture_rwlock_write_unlock_irq(int tid __maybe_unused)
 __releases(torture_rwlock)
 {
     write_unlock_irqrestore(&torture_rwlock, cxt.cur_ops->flags);
 }
 
 static int torture_rwlock_read_lock_irq(int tid __maybe_unused)
 __acquires(torture_rwlock)
 {
     unsigned long flags;
 
     read_lock_irqsave(&torture_rwlock, flags);
     cxt.cur_ops->flags = flags;
     return 0;
 }
 
 static void torture_rwlock_read_unlock_irq(int tid __maybe_unused)
 __releases(torture_rwlock)
 {
     read_unlock_irqrestore(&torture_rwlock, cxt.cur_ops->flags);
 }
 
 static struct lock_torture_ops rw_lock_irq_ops = {
     .writelock  = torture_rwlock_write_lock_irq,
     .write_delay    = torture_rwlock_write_delay,
     .task_boost     = torture_boost_dummy,
     .writeunlock    = torture_rwlock_write_unlock_irq,
     .readlock       = torture_rwlock_read_lock_irq,
     .read_delay     = torture_rwlock_read_delay,
     .readunlock     = torture_rwlock_read_unlock_irq,
     .name       = "rw_lock_irq"
 };
 
 static DEFINE_MUTEX(torture_mutex);
 
 static int torture_mutex_lock(int tid __maybe_unused)
 __acquires(torture_mutex)
 {
     mutex_lock(&torture_mutex);
     return 0;
 }
 
 static void torture_mutex_delay(struct torture_random_state *trsp)
 {
     const unsigned long longdelay_ms = 100;
 
     /* We want a long delay occasionally to force massive contention.  */
     if (!(torture_random(trsp) %
           (cxt.nrealwriters_stress * 2000 * longdelay_ms)))
         mdelay(longdelay_ms * 5);
     else
         mdelay(longdelay_ms / 5);
     if (!(torture_random(trsp) % (cxt.nrealwriters_stress * 20000)))
         torture_preempt_schedule();  /* Allow test to be preempted. */
 }
 
 static void torture_mutex_unlock(int tid __maybe_unused)
 __releases(torture_mutex)
 {
     mutex_unlock(&torture_mutex);
 }
 
 static struct lock_torture_ops mutex_lock_ops = {
     .writelock  = torture_mutex_lock,
     .write_delay    = torture_mutex_delay,
     .task_boost     = torture_boost_dummy,
     .writeunlock    = torture_mutex_unlock,
     .readlock       = NULL,
     .read_delay     = NULL,
     .readunlock     = NULL,
     .name       = "mutex_lock"
 };
 
 #include <linux/ww_mutex.h>
 /*
  * The torture ww_mutexes should belong to the same lock class as
  * torture_ww_class to avoid lockdep problem. The ww_mutex_init()
  * function is called for initialization to ensure that.
  */
 static DEFINE_WD_CLASS(torture_ww_class);
 static struct ww_mutex torture_ww_mutex_0, torture_ww_mutex_1, torture_ww_mutex_2;
 static struct ww_acquire_ctx *ww_acquire_ctxs;
 
 static void torture_ww_mutex_init(void)
 {
     ww_mutex_init(&torture_ww_mutex_0, &torture_ww_class);
     ww_mutex_init(&torture_ww_mutex_1, &torture_ww_class);
     ww_mutex_init(&torture_ww_mutex_2, &torture_ww_class);
 
     ww_acquire_ctxs = kmalloc_array(cxt.nrealwriters_stress,
                     sizeof(*ww_acquire_ctxs),
                     GFP_KERNEL);
     if (!ww_acquire_ctxs)
         VERBOSE_TOROUT_STRING("ww_acquire_ctx: Out of memory");
 }
 
 static void torture_ww_mutex_exit(void)
 {
     kfree(ww_acquire_ctxs);
 }
 
 static int torture_ww_mutex_lock(int tid)
 __acquires(torture_ww_mutex_0)
 __acquires(torture_ww_mutex_1)
 __acquires(torture_ww_mutex_2)
 {
     LIST_HEAD(list);
     struct reorder_lock {
         struct list_head link;
         struct ww_mutex *lock;
     } locks[3], *ll, *ln;
     struct ww_acquire_ctx *ctx = &ww_acquire_ctxs[tid];
 
     locks[0].lock = &torture_ww_mutex_0;
     list_add(&locks[0].link, &list);
 
     locks[1].lock = &torture_ww_mutex_1;
     list_add(&locks[1].link, &list);
 
     locks[2].lock = &torture_ww_mutex_2;
     list_add(&locks[2].link, &list);
 
     ww_acquire_init(ctx, &torture_ww_class);
 
     list_for_each_entry(ll, &list, link) {
         int err;
 
         err = ww_mutex_lock(ll->lock, ctx);
         if (!err)
             continue;
 
         ln = ll;
         list_for_each_entry_continue_reverse(ln, &list, link)
             ww_mutex_unlock(ln->lock);
 
         if (err != -EDEADLK)
             return err;
 
         ww_mutex_lock_slow(ll->lock, ctx);
         list_move(&ll->link, &list);
     }
 
     return 0;
 }
 
 static void torture_ww_mutex_unlock(int tid)
 __releases(torture_ww_mutex_0)
 __releases(torture_ww_mutex_1)
 __releases(torture_ww_mutex_2)
 {
     struct ww_acquire_ctx *ctx = &ww_acquire_ctxs[tid];
 
     ww_mutex_unlock(&torture_ww_mutex_0);
     ww_mutex_unlock(&torture_ww_mutex_1);
     ww_mutex_unlock(&torture_ww_mutex_2);
     ww_acquire_fini(ctx);
 }
 
 static struct lock_torture_ops ww_mutex_lock_ops = {
     .init       = torture_ww_mutex_init,
     .exit       = torture_ww_mutex_exit,
     .writelock  = torture_ww_mutex_lock,
     .write_delay    = torture_mutex_delay,
     .task_boost     = torture_boost_dummy,
     .writeunlock    = torture_ww_mutex_unlock,
     .readlock       = NULL,
     .read_delay     = NULL,
     .readunlock     = NULL,
     .name       = "ww_mutex_lock"
 };
 
 #ifdef CONFIG_RT_MUTEXES
 static DEFINE_RT_MUTEX(torture_rtmutex);
 
 static int torture_rtmutex_lock(int tid __maybe_unused)
 __acquires(torture_rtmutex)
 {
     rt_mutex_lock(&torture_rtmutex);
     return 0;
 }
 
 static void torture_rtmutex_boost(struct torture_random_state *trsp)
 {
     const unsigned int factor = 50000; /* yes, quite arbitrary */
 
     if (!rt_task(current)) {
         /*
          * Boost priority once every ~50k operations. When the
          * task tries to take the lock, the rtmutex it will account
          * for the new priority, and do any corresponding pi-dance.
          */
         if (trsp && !(torture_random(trsp) %
                   (cxt.nrealwriters_stress * factor))) {
             sched_set_fifo(current);
         } else /* common case, do nothing */
             return;
     } else {
         /*
          * The task will remain boosted for another ~500k operations,
          * then restored back to its original prio, and so forth.
          *
          * When @trsp is nil, we want to force-reset the task for
          * stopping the kthread.
          */
         if (!trsp || !(torture_random(trsp) %
                    (cxt.nrealwriters_stress * factor * 2))) {
             sched_set_normal(current, 0);
         } else /* common case, do nothing */
             return;
     }
 }
 
 static void torture_rtmutex_delay(struct torture_random_state *trsp)
 {
     const unsigned long shortdelay_us = 2;
     const unsigned long longdelay_ms = 100;
 
     /*
      * We want a short delay mostly to emulate likely code, and
      * we want a long delay occasionally to force massive contention.
      */
     if (!(torture_random(trsp) %
           (cxt.nrealwriters_stress * 2000 * longdelay_ms)))
         mdelay(longdelay_ms);
     if (!(torture_random(trsp) %
           (cxt.nrealwriters_stress * 2 * shortdelay_us)))
         udelay(shortdelay_us);
     if (!(torture_random(trsp) % (cxt.nrealwriters_stress * 20000)))
         torture_preempt_schedule();  /* Allow test to be preempted. */
 }
 
 static void torture_rtmutex_unlock(int tid __maybe_unused)
 __releases(torture_rtmutex)
 {
     rt_mutex_unlock(&torture_rtmutex);
 }
 
 static struct lock_torture_ops rtmutex_lock_ops = {
     .writelock  = torture_rtmutex_lock,
     .write_delay    = torture_rtmutex_delay,
     .task_boost     = torture_rtmutex_boost,
     .writeunlock    = torture_rtmutex_unlock,
     .readlock       = NULL,
     .read_delay     = NULL,
     .readunlock     = NULL,
     .name       = "rtmutex_lock"
 };
 #endif
 
 static DECLARE_RWSEM(torture_rwsem);
 static int torture_rwsem_down_write(int tid __maybe_unused)
 __acquires(torture_rwsem)
 {
     down_write(&torture_rwsem);
     return 0;
 }
 
 static void torture_rwsem_write_delay(struct torture_random_state *trsp)
 {
     const unsigned long longdelay_ms = 100;
 
     /* We want a long delay occasionally to force massive contention.  */
     if (!(torture_random(trsp) %
           (cxt.nrealwriters_stress * 2000 * longdelay_ms)))
         mdelay(longdelay_ms * 10);
     else
         mdelay(longdelay_ms / 10);
     if (!(torture_random(trsp) % (cxt.nrealwriters_stress * 20000)))
         torture_preempt_schedule();  /* Allow test to be preempted. */
 }
 
 static void torture_rwsem_up_write(int tid __maybe_unused)
 __releases(torture_rwsem)
 {
     up_write(&torture_rwsem);
 }
 
 static int torture_rwsem_down_read(int tid __maybe_unused)
 __acquires(torture_rwsem)
 {
     down_read(&torture_rwsem);
     return 0;
 }
 
 static void torture_rwsem_read_delay(struct torture_random_state *trsp)
 {
     const unsigned long longdelay_ms = 100;
 
     /* We want a long delay occasionally to force massive contention.  */
     if (!(torture_random(trsp) %
           (cxt.nrealreaders_stress * 2000 * longdelay_ms)))
         mdelay(longdelay_ms * 2);
     else
         mdelay(longdelay_ms / 2);
     if (!(torture_random(trsp) % (cxt.nrealreaders_stress * 20000)))
         torture_preempt_schedule();  /* Allow test to be preempted. */
 }
 
 static void torture_rwsem_up_read(int tid __maybe_unused)
 __releases(torture_rwsem)
 {
     up_read(&torture_rwsem);
 }
 
 static struct lock_torture_ops rwsem_lock_ops = {
     .writelock  = torture_rwsem_down_write,
     .write_delay    = torture_rwsem_write_delay,
     .task_boost     = torture_boost_dummy,
     .writeunlock    = torture_rwsem_up_write,
     .readlock       = torture_rwsem_down_read,
     .read_delay     = torture_rwsem_read_delay,
     .readunlock     = torture_rwsem_up_read,
     .name       = "rwsem_lock"
 };
 
 #include <linux/percpu-rwsem.h>
 static struct percpu_rw_semaphore pcpu_rwsem;
 
 static void torture_percpu_rwsem_init(void)
 {
     BUG_ON(percpu_init_rwsem(&pcpu_rwsem));
 }
 
 static void torture_percpu_rwsem_exit(void)
 {
     percpu_free_rwsem(&pcpu_rwsem);
 }
 
 static int torture_percpu_rwsem_down_write(int tid __maybe_unused)
 __acquires(pcpu_rwsem)
 {
     percpu_down_write(&pcpu_rwsem);
     return 0;
 }
 
 static void torture_percpu_rwsem_up_write(int tid __maybe_unused)
 __releases(pcpu_rwsem)
 {
     percpu_up_write(&pcpu_rwsem);
 }
 
 static int torture_percpu_rwsem_down_read(int tid __maybe_unused)
 __acquires(pcpu_rwsem)
 {
     percpu_down_read(&pcpu_rwsem);
     return 0;
 }
 
 static void torture_percpu_rwsem_up_read(int tid __maybe_unused)
 __releases(pcpu_rwsem)
 {
     percpu_up_read(&pcpu_rwsem);
 }
 
 static struct lock_torture_ops percpu_rwsem_lock_ops = {
     .init       = torture_percpu_rwsem_init,
     .exit       = torture_percpu_rwsem_exit,
     .writelock  = torture_percpu_rwsem_down_write,
     .write_delay    = torture_rwsem_write_delay,
     .task_boost     = torture_boost_dummy,
     .writeunlock    = torture_percpu_rwsem_up_write,
     .readlock       = torture_percpu_rwsem_down_read,
     .read_delay     = torture_rwsem_read_delay,
     .readunlock     = torture_percpu_rwsem_up_read,
     .name       = "percpu_rwsem_lock"
 };
 
 /*
  * Lock torture writer kthread.  Repeatedly acquires and releases
  * the lock, checking for duplicate acquisitions.
  */
 static int lock_torture_writer(void *arg)
 {
     struct lock_stress_stats *lwsp = arg;
     int tid = lwsp - cxt.lwsa;
     DEFINE_TORTURE_RANDOM(rand);
 
     VERBOSE_TOROUT_STRING("lock_torture_writer task started");
     set_user_nice(current, MAX_NICE);
 
     do {
         if ((torture_random(&rand) & 0xfffff) == 0)
             schedule_timeout_uninterruptible(1);
 
         cxt.cur_ops->task_boost(&rand);
         cxt.cur_ops->writelock(tid);
         if (WARN_ON_ONCE(lock_is_write_held))
             lwsp->n_lock_fail++;
         lock_is_write_held = true;
         if (WARN_ON_ONCE(atomic_read(&lock_is_read_held)))
             lwsp->n_lock_fail++; /* rare, but... */
 
         lwsp->n_lock_acquired++;
         cxt.cur_ops->write_delay(&rand);
         lock_is_write_held = false;
         WRITE_ONCE(last_lock_release, jiffies);
         cxt.cur_ops->writeunlock(tid);
 
         stutter_wait("lock_torture_writer");
     } while (!torture_must_stop());
 
     cxt.cur_ops->task_boost(NULL); /* reset prio */
     torture_kthread_stopping("lock_torture_writer");
     return 0;
 }
 
 /*
  * Lock torture reader kthread.  Repeatedly acquires and releases
  * the reader lock.
  */
 static int lock_torture_reader(void *arg)
 {
     struct lock_stress_stats *lrsp = arg;
     int tid = lrsp - cxt.lrsa;
     DEFINE_TORTURE_RANDOM(rand);
 
     VERBOSE_TOROUT_STRING("lock_torture_reader task started");
     set_user_nice(current, MAX_NICE);
 
     do {
         if ((torture_random(&rand) & 0xfffff) == 0)
             schedule_timeout_uninterruptible(1);
 
         cxt.cur_ops->readlock(tid);
         atomic_inc(&lock_is_read_held);
         if (WARN_ON_ONCE(lock_is_write_held))
             lrsp->n_lock_fail++; /* rare, but... */
 
         lrsp->n_lock_acquired++;
         cxt.cur_ops->read_delay(&rand);
         atomic_dec(&lock_is_read_held);
         cxt.cur_ops->readunlock(tid);
 
         stutter_wait("lock_torture_reader");
     } while (!torture_must_stop());
     torture_kthread_stopping("lock_torture_reader");
     return 0;
 }
 
 /*
  * Create an lock-torture-statistics message in the specified buffer.
  */
 static void __torture_print_stats(char *page,
                   struct lock_stress_stats *statp, bool write)
 {
     long cur;
     bool fail = false;
     int i, n_stress;
     long max = 0, min = statp ? data_race(statp[0].n_lock_acquired) : 0;
     long long sum = 0;
 
     n_stress = write ? cxt.nrealwriters_stress : cxt.nrealreaders_stress;
     for (i = 0; i < n_stress; i++) {
         if (data_race(statp[i].n_lock_fail))
             fail = true;
         cur = data_race(statp[i].n_lock_acquired);
         sum += cur;
         if (max < cur)
             max = cur;
         if (min > cur)
             min = cur;
     }
     page += sprintf(page,
             "%s:  Total: %lld  Max/Min: %ld/%ld %s  Fail: %d %s\n",
             write ? "Writes" : "Reads ",
             sum, max, min,
             !onoff_interval && max / 2 > min ? "???" : "",
             fail, fail ? "!!!" : "");
     if (fail)
         atomic_inc(&cxt.n_lock_torture_errors);
 }
 
 /*
  * Print torture statistics.  Caller must ensure that there is only one
  * call to this function at a given time!!!  This is normally accomplished
  * by relying on the module system to only have one copy of the module
  * loaded, and then by giving the lock_torture_stats kthread full control
  * (or the init/cleanup functions when lock_torture_stats thread is not
  * running).
  */
 static void lock_torture_stats_print(void)
 {
     int size = cxt.nrealwriters_stress * 200 + 8192;
     char *buf;
 
     if (cxt.cur_ops->readlock)
         size += cxt.nrealreaders_stress * 200 + 8192;
 
     buf = kmalloc(size, GFP_KERNEL);
     if (!buf) {
         pr_err("lock_torture_stats_print: Out of memory, need: %d",
                size);
         return;
     }
 
     __torture_print_stats(buf, cxt.lwsa, true);
     pr_alert("%s", buf);
     kfree(buf);
 
     if (cxt.cur_ops->readlock) {
         buf = kmalloc(size, GFP_KERNEL);
         if (!buf) {
             pr_err("lock_torture_stats_print: Out of memory, need: %d",
                    size);
             return;
         }
 
         __torture_print_stats(buf, cxt.lrsa, false);
         pr_alert("%s", buf);
         kfree(buf);
     }
 }
 
 /*
  * Periodically prints torture statistics, if periodic statistics printing
  * was specified via the stat_interval module parameter.
  *
  * No need to worry about fullstop here, since this one doesn't reference
  * volatile state or register callbacks.
  */
 static int lock_torture_stats(void *arg)
 {
     VERBOSE_TOROUT_STRING("lock_torture_stats task started");
     do {
         schedule_timeout_interruptible(stat_interval * HZ);
         lock_torture_stats_print();
         torture_shutdown_absorb("lock_torture_stats");
     } while (!torture_must_stop());
     torture_kthread_stopping("lock_torture_stats");
     return 0;
 }
 
 static inline void
 lock_torture_print_module_parms(struct lock_torture_ops *cur_ops,
                 const char *tag)
 {
     pr_alert("%s" TORTURE_FLAG
          "--- %s%s: nwriters_stress=%d nreaders_stress=%d stat_interval=%d verbose=%d shuffle_interval=%d stutter=%d shutdown_secs=%d onoff_interval=%d onoff_holdoff=%d\n",
          torture_type, tag, cxt.debug_lock ? " [debug]": "",
          cxt.nrealwriters_stress, cxt.nrealreaders_stress, stat_interval,
          verbose, shuffle_interval, stutter, shutdown_secs,
          onoff_interval, onoff_holdoff);
 }
 
 static void lock_torture_cleanup(void)
 {
     int i;
 
     if (torture_cleanup_begin())
         return;
 
     /*
      * Indicates early cleanup, meaning that the test has not run,
      * such as when passing bogus args when loading the module.
      * However cxt->cur_ops.init() may have been invoked, so beside
      * perform the underlying torture-specific cleanups, cur_ops.exit()
      * will be invoked if needed.
      */
     if (!cxt.lwsa && !cxt.lrsa)
         goto end;
 
     if (writer_tasks) {
         for (i = 0; i < cxt.nrealwriters_stress; i++)
             torture_stop_kthread(lock_torture_writer,
                          writer_tasks[i]);
         kfree(writer_tasks);
         writer_tasks = NULL;
     }
 
     if (reader_tasks) {
         for (i = 0; i < cxt.nrealreaders_stress; i++)
             torture_stop_kthread(lock_torture_reader,
                          reader_tasks[i]);
         kfree(reader_tasks);
         reader_tasks = NULL;
     }
 
     torture_stop_kthread(lock_torture_stats, stats_task);
     lock_torture_stats_print();  /* -After- the stats thread is stopped! */
 
     if (atomic_read(&cxt.n_lock_torture_errors))
         lock_torture_print_module_parms(cxt.cur_ops,
                         "End of test: FAILURE");
     else if (torture_onoff_failures())
         lock_torture_print_module_parms(cxt.cur_ops,
                         "End of test: LOCK_HOTPLUG");
     else
         lock_torture_print_module_parms(cxt.cur_ops,
                         "End of test: SUCCESS");
 
     kfree(cxt.lwsa);
     cxt.lwsa = NULL;
     kfree(cxt.lrsa);
     cxt.lrsa = NULL;
 
 end:
     if (cxt.init_called) {
         if (cxt.cur_ops->exit)
             cxt.cur_ops->exit();
         cxt.init_called = false;
     }
     torture_cleanup_end();
 }
 
 static int __init lock_torture_init(void)
 {
     int i, j;
     int firsterr = 0;
     static struct lock_torture_ops *torture_ops[] = {
         &lock_busted_ops,
         &spin_lock_ops, &spin_lock_irq_ops,
         &rw_lock_ops, &rw_lock_irq_ops,
         &mutex_lock_ops,
         &ww_mutex_lock_ops,
 #ifdef CONFIG_RT_MUTEXES
         &rtmutex_lock_ops,
 #endif
         &rwsem_lock_ops,
         &percpu_rwsem_lock_ops,
     };
 
     if (!torture_init_begin(torture_type, verbose))
         return -EBUSY;
 
     /* Process args and tell the world that the torturer is on the job. */
     for (i = 0; i < ARRAY_SIZE(torture_ops); i++) {
         cxt.cur_ops = torture_ops[i];
         if (strcmp(torture_type, cxt.cur_ops->name) == 0)
             break;
     }
     if (i == ARRAY_SIZE(torture_ops)) {
         pr_alert("lock-torture: invalid torture type: \"%s\"\n",
              torture_type);
         pr_alert("lock-torture types:");
         for (i = 0; i < ARRAY_SIZE(torture_ops); i++)
             pr_alert(" %s", torture_ops[i]->name);
         pr_alert("\n");
         firsterr = -EINVAL;
         goto unwind;
     }
 
     if (nwriters_stress == 0 &&
         (!cxt.cur_ops->readlock || nreaders_stress == 0)) {
         pr_alert("lock-torture: must run at least one locking thread\n");
         firsterr = -EINVAL;
         goto unwind;
     }
 
     if (nwriters_stress >= 0)
         cxt.nrealwriters_stress = nwriters_stress;
     else
         cxt.nrealwriters_stress = 2 * num_online_cpus();
 
     if (cxt.cur_ops->init) {
         cxt.cur_ops->init();
         cxt.init_called = true;
     }
 
 #ifdef CONFIG_DEBUG_MUTEXES
     if (str_has_prefix(torture_type, "mutex"))
         cxt.debug_lock = true;
 #endif
 #ifdef CONFIG_DEBUG_RT_MUTEXES
     if (str_has_prefix(torture_type, "rtmutex"))
         cxt.debug_lock = true;
 #endif
 #ifdef CONFIG_DEBUG_SPINLOCK
     if ((str_has_prefix(torture_type, "spin")) ||
         (str_has_prefix(torture_type, "rw_lock")))
         cxt.debug_lock = true;
 #endif
 
     /* Initialize the statistics so that each run gets its own numbers. */
     if (nwriters_stress) {
         lock_is_write_held = false;
         cxt.lwsa = kmalloc_array(cxt.nrealwriters_stress,
                      sizeof(*cxt.lwsa),
                      GFP_KERNEL);
         if (cxt.lwsa == NULL) {
             VERBOSE_TOROUT_STRING("cxt.lwsa: Out of memory");
             firsterr = -ENOMEM;
             goto unwind;
         }
 
         for (i = 0; i < cxt.nrealwriters_stress; i++) {
             cxt.lwsa[i].n_lock_fail = 0;
             cxt.lwsa[i].n_lock_acquired = 0;
         }
     }
 
     if (cxt.cur_ops->readlock) {
         if (nreaders_stress >= 0)
             cxt.nrealreaders_stress = nreaders_stress;
         else {
             /*
              * By default distribute evenly the number of
              * readers and writers. We still run the same number
              * of threads as the writer-only locks default.
              */
             if (nwriters_stress < 0) /* user doesn't care */
                 cxt.nrealwriters_stress = num_online_cpus();
             cxt.nrealreaders_stress = cxt.nrealwriters_stress;
         }
 
         if (nreaders_stress) {
             cxt.lrsa = kmalloc_array(cxt.nrealreaders_stress,
                          sizeof(*cxt.lrsa),
                          GFP_KERNEL);
             if (cxt.lrsa == NULL) {
                 VERBOSE_TOROUT_STRING("cxt.lrsa: Out of memory");
                 firsterr = -ENOMEM;
                 kfree(cxt.lwsa);
                 cxt.lwsa = NULL;
                 goto unwind;
             }
 
             for (i = 0; i < cxt.nrealreaders_stress; i++) {
                 cxt.lrsa[i].n_lock_fail = 0;
                 cxt.lrsa[i].n_lock_acquired = 0;
             }
         }
     }
 
     lock_torture_print_module_parms(cxt.cur_ops, "Start of test");
 
     /* Prepare torture context. */
     if (onoff_interval > 0) {
         firsterr = torture_onoff_init(onoff_holdoff * HZ,
                           onoff_interval * HZ, NULL);
         if (torture_init_error(firsterr))
             goto unwind;
     }
     if (shuffle_interval > 0) {
         firsterr = torture_shuffle_init(shuffle_interval);
         if (torture_init_error(firsterr))
             goto unwind;
     }
     if (shutdown_secs > 0) {
         firsterr = torture_shutdown_init(shutdown_secs,
                          lock_torture_cleanup);
         if (torture_init_error(firsterr))
             goto unwind;
     }
     if (stutter > 0) {
         firsterr = torture_stutter_init(stutter, stutter);
         if (torture_init_error(firsterr))
             goto unwind;
     }
 
     if (nwriters_stress) {
         writer_tasks = kcalloc(cxt.nrealwriters_stress,
                        sizeof(writer_tasks[0]),
                        GFP_KERNEL);
         if (writer_tasks == NULL) {
             TOROUT_ERRSTRING("writer_tasks: Out of memory");
             firsterr = -ENOMEM;
             goto unwind;
         }
     }
 
     if (cxt.cur_ops->readlock) {
         reader_tasks = kcalloc(cxt.nrealreaders_stress,
                        sizeof(reader_tasks[0]),
                        GFP_KERNEL);
         if (reader_tasks == NULL) {
             TOROUT_ERRSTRING("reader_tasks: Out of memory");
             kfree(writer_tasks);
             writer_tasks = NULL;
             firsterr = -ENOMEM;
             goto unwind;
         }
     }
 
     /*
      * Create the kthreads and start torturing (oh, those poor little locks).
      *
      * TODO: Note that we interleave writers with readers, giving writers a
      * slight advantage, by creating its kthread first. This can be modified
      * for very specific needs, or even let the user choose the policy, if
      * ever wanted.
      */
     for (i = 0, j = 0; i < cxt.nrealwriters_stress ||
             j < cxt.nrealreaders_stress; i++, j++) {
         if (i >= cxt.nrealwriters_stress)
             goto create_reader;
 
         /* Create writer. */
         firsterr = torture_create_kthread(lock_torture_writer, &cxt.lwsa[i],
                           writer_tasks[i]);
         if (torture_init_error(firsterr))
             goto unwind;
 
     create_reader:
         if (cxt.cur_ops->readlock == NULL || (j >= cxt.nrealreaders_stress))
             continue;
         /* Create reader. */
         firsterr = torture_create_kthread(lock_torture_reader, &cxt.lrsa[j],
                           reader_tasks[j]);
         if (torture_init_error(firsterr))
             goto unwind;
     }
     if (stat_interval > 0) {
         firsterr = torture_create_kthread(lock_torture_stats, NULL,
                           stats_task);
         if (torture_init_error(firsterr))
             goto unwind;
     }
     torture_init_end();
     return 0;
 
 unwind:
     torture_init_end();
     lock_torture_cleanup();
     if (shutdown_secs) {
         WARN_ON(!IS_MODULE(CONFIG_LOCK_TORTURE_TEST));
         kernel_power_off();
     }
     return firsterr;
 }
 
 module_init(lock_torture_init);
 module_exit(lock_torture_cleanup);

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