ClabureDB: Classified Bug-Reports Database

   /*
    * Read-Copy Update module-based torture test facility
    *
    * This program is free software; you can redistribute it and/or modify
    * it under the terms of the GNU General Public License as published by
    * the Free Software Foundation; either version 2 of the License, or
    * (at your option) any later version.
    *
    * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
   *
   * Copyright (C) IBM Corporation, 2005, 2006
   *
   * Authors: Paul E. McKenney <paulmck@us.ibm.com>
   *          Josh Triplett <josh@freedesktop.org>
   *
   * See also:  Documentation/RCU/torture.txt
   */
  #include <linux/types.h>
  #include <linux/kernel.h>
  #include <linux/init.h>
  #include <linux/module.h>
  #include <linux/kthread.h>
  #include <linux/err.h>
  #include <linux/spinlock.h>
  #include <linux/smp.h>
  #include <linux/rcupdate.h>
  #include <linux/interrupt.h>
  #include <linux/sched.h>
  #include <asm/atomic.h>
  #include <linux/bitops.h>
  #include <linux/completion.h>
  #include <linux/moduleparam.h>
  #include <linux/percpu.h>
  #include <linux/notifier.h>
  #include <linux/freezer.h>
  #include <linux/cpu.h>
  #include <linux/delay.h>
  #include <linux/stat.h>
  #include <linux/srcu.h>
  #include <linux/slab.h>
  #include <asm/byteorder.h>
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Paul E. McKenney <paulmck@us.ibm.com> and "
                "Josh Triplett <josh@freedesktop.org>");
  
  static int nreaders = -1;        /* # reader threads, defaults to 2*ncpus */
  static int nfakewriters = 4;        /* # fake writer threads */
  static int stat_interval;        /* Interval between stats, in seconds. */
                                  /*  Defaults to "only at end of test". */
  static int verbose;                /* Print more debug info. */
  static int test_no_idle_hz;        /* Test RCU's support for tickless idle CPUs. */
  static int shuffle_interval = 3; /* Interval between shuffles (in sec)*/
  static int stutter = 5;                /* Start/stop testing interval (in sec) */
  static int irqreader = 1;        /* RCU readers from irq (timers). */
  static char *torture_type = "rcu"; /* What RCU implementation to torture. */
  
  module_param(nreaders, int, 0444);
  MODULE_PARM_DESC(nreaders, "Number of RCU reader threads");
  module_param(nfakewriters, int, 0444);
  MODULE_PARM_DESC(nfakewriters, "Number of RCU fake writer threads");
  module_param(stat_interval, int, 0444);
  MODULE_PARM_DESC(stat_interval, "Number of seconds between stats printk()s");
  module_param(verbose, bool, 0444);
  MODULE_PARM_DESC(verbose, "Enable verbose debugging printk()s");
  module_param(test_no_idle_hz, bool, 0444);
  MODULE_PARM_DESC(test_no_idle_hz, "Test support for tickless idle CPUs");
  module_param(shuffle_interval, int, 0444);
  MODULE_PARM_DESC(shuffle_interval, "Number of seconds between shuffles");
  module_param(stutter, int, 0444);
  MODULE_PARM_DESC(stutter, "Number of seconds to run/halt test");
  module_param(irqreader, int, 0444);
  MODULE_PARM_DESC(irqreader, "Allow RCU readers from irq handlers");
  module_param(torture_type, charp, 0444);
  MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, rcu_bh, srcu)");
  
  #define TORTURE_FLAG "-torture:"
  #define PRINTK_STRING(s) \
          do { printk(KERN_ALERT "%s" TORTURE_FLAG s "\n", torture_type); } while (0)
  #define VERBOSE_PRINTK_STRING(s) \
          do { if (verbose) printk(KERN_ALERT "%s" TORTURE_FLAG s "\n", torture_type); } while (0)
  #define VERBOSE_PRINTK_ERRSTRING(s) \
          do { if (verbose) printk(KERN_ALERT "%s" TORTURE_FLAG "!!! " s "\n", torture_type); } while (0)
  
  static char printk_buf[4096];
  
  static int nrealreaders;
  static struct task_struct *writer_task;
  static struct task_struct **fakewriter_tasks;
  static struct task_struct **reader_tasks;
  static struct task_struct *stats_task;
  static struct task_struct *shuffler_task;
 static struct task_struct *stutter_task;
 
 #define RCU_TORTURE_PIPE_LEN 10
 
 struct rcu_torture {
         struct rcu_head rtort_rcu;
         int rtort_pipe_count;
         struct list_head rtort_free;
         int rtort_mbtest;
 };
 
 static int fullstop = 0;        /* stop generating callbacks at test end. */
 static LIST_HEAD(rcu_torture_freelist);
 static struct rcu_torture *rcu_torture_current = NULL;
 static long rcu_torture_current_version = 0;
 static struct rcu_torture rcu_tortures[10 * RCU_TORTURE_PIPE_LEN];
 static DEFINE_SPINLOCK(rcu_torture_lock);
 static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_count) =
         { 0 };
 static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_batch) =
         { 0 };
 static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1];
 static atomic_t n_rcu_torture_alloc;
 static atomic_t n_rcu_torture_alloc_fail;
 static atomic_t n_rcu_torture_free;
 static atomic_t n_rcu_torture_mberror;
 static atomic_t n_rcu_torture_error;
 static long n_rcu_torture_timers = 0;
 static struct list_head rcu_torture_removed;
 
 static int stutter_pause_test = 0;
 
 #if defined(MODULE) || defined(CONFIG_RCU_TORTURE_TEST_RUNNABLE)
 #define RCUTORTURE_RUNNABLE_INIT 1
 #else
 #define RCUTORTURE_RUNNABLE_INIT 0
 #endif
 int rcutorture_runnable = RCUTORTURE_RUNNABLE_INIT;
 
 /*
  * Allocate an element from the rcu_tortures pool.
  */
 static struct rcu_torture *
 rcu_torture_alloc(void)
 {
         struct list_head *p;
 
         spin_lock_bh(&rcu_torture_lock);
         if (list_empty(&rcu_torture_freelist)) {
                 atomic_inc(&n_rcu_torture_alloc_fail);
                 spin_unlock_bh(&rcu_torture_lock);
                 return NULL;
         }
         atomic_inc(&n_rcu_torture_alloc);
         p = rcu_torture_freelist.next;
         list_del_init(p);
         spin_unlock_bh(&rcu_torture_lock);
         return container_of(p, struct rcu_torture, rtort_free);
 }
 
 /*
  * Free an element to the rcu_tortures pool.
  */
 static void
 rcu_torture_free(struct rcu_torture *p)
 {
         atomic_inc(&n_rcu_torture_free);
         spin_lock_bh(&rcu_torture_lock);
         list_add_tail(&p->rtort_free, &rcu_torture_freelist);
         spin_unlock_bh(&rcu_torture_lock);
 }
 
 struct rcu_random_state {
         unsigned long rrs_state;
         long rrs_count;
 };
 
 #define RCU_RANDOM_MULT 39916801  /* prime */
 #define RCU_RANDOM_ADD        479001701 /* prime */
 #define RCU_RANDOM_REFRESH 10000
 
 #define DEFINE_RCU_RANDOM(name) struct rcu_random_state name = { 0, 0 }
 
 /*
  * Crude but fast random-number generator.  Uses a linear congruential
  * generator, with occasional help from cpu_clock().
  */
 static unsigned long
 rcu_random(struct rcu_random_state *rrsp)
 {
         if (--rrsp->rrs_count < 0) {
                 rrsp->rrs_state +=
                         (unsigned long)cpu_clock(raw_smp_processor_id());
                 rrsp->rrs_count = RCU_RANDOM_REFRESH;
         }
         rrsp->rrs_state = rrsp->rrs_state * RCU_RANDOM_MULT + RCU_RANDOM_ADD;
         return swahw32(rrsp->rrs_state);
 }
 
 static void
 rcu_stutter_wait(void)
 {
         while (stutter_pause_test || !rcutorture_runnable)
                 if (rcutorture_runnable)
                         schedule_timeout_interruptible(1);
                 else
                         schedule_timeout_interruptible(round_jiffies_relative(HZ));
 }
 
 /*
  * Operations vector for selecting different types of tests.
  */
 
 struct rcu_torture_ops {
         void (*init)(void);
         void (*cleanup)(void);
         int (*readlock)(void);
         void (*readdelay)(struct rcu_random_state *rrsp);
         void (*readunlock)(int idx);
         int (*completed)(void);
         void (*deferredfree)(struct rcu_torture *p);
         void (*sync)(void);
         void (*cb_barrier)(void);
         int (*stats)(char *page);
         int irqcapable;
         char *name;
 };
 static struct rcu_torture_ops *cur_ops = NULL;
 
 /*
  * Definitions for rcu torture testing.
  */
 
 static int rcu_torture_read_lock(void) __acquires(RCU)
 {
         rcu_read_lock();
         return 0;
 }
 
 static void rcu_read_delay(struct rcu_random_state *rrsp)
 {
         long delay;
         const long longdelay = 200;
 
         /* We want there to be long-running readers, but not all the time. */
 
         delay = rcu_random(rrsp) % (nrealreaders * 2 * longdelay);
         if (!delay)
                 udelay(longdelay);
 }
 
 static void rcu_torture_read_unlock(int idx) __releases(RCU)
 {
         rcu_read_unlock();
 }
 
 static int rcu_torture_completed(void)
 {
         return rcu_batches_completed();
 }
 
 static void
 rcu_torture_cb(struct rcu_head *p)
 {
         int i;
         struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu);
 
         if (fullstop) {
                 /* Test is ending, just drop callbacks on the floor. */
                 /* The next initialization will pick up the pieces. */
                 return;
         }
         i = rp->rtort_pipe_count;
         if (i > RCU_TORTURE_PIPE_LEN)
                 i = RCU_TORTURE_PIPE_LEN;
         atomic_inc(&rcu_torture_wcount[i]);
         if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
                 rp->rtort_mbtest = 0;
                 rcu_torture_free(rp);
         } else
                 cur_ops->deferredfree(rp);
 }
 
 static void rcu_torture_deferred_free(struct rcu_torture *p)
 {
         call_rcu(&p->rtort_rcu, rcu_torture_cb);
 }
 
 static struct rcu_torture_ops rcu_ops = {
         .init = NULL,
         .cleanup = NULL,
         .readlock = rcu_torture_read_lock,
         .readdelay = rcu_read_delay,
         .readunlock = rcu_torture_read_unlock,
         .completed = rcu_torture_completed,
         .deferredfree = rcu_torture_deferred_free,
         .sync = synchronize_rcu,
         .cb_barrier = rcu_barrier,
         .stats = NULL,
         .irqcapable = 1,
         .name = "rcu"
 };
 
 static void rcu_sync_torture_deferred_free(struct rcu_torture *p)
 {
         int i;
         struct rcu_torture *rp;
         struct rcu_torture *rp1;
 
         cur_ops->sync();
         list_add(&p->rtort_free, &rcu_torture_removed);
         list_for_each_entry_safe(rp, rp1, &rcu_torture_removed, rtort_free) {
                 i = rp->rtort_pipe_count;
                 if (i > RCU_TORTURE_PIPE_LEN)
                         i = RCU_TORTURE_PIPE_LEN;
                 atomic_inc(&rcu_torture_wcount[i]);
                 if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
                         rp->rtort_mbtest = 0;
                         list_del(&rp->rtort_free);
                         rcu_torture_free(rp);
                 }
         }
 }
 
 static void rcu_sync_torture_init(void)
 {
         INIT_LIST_HEAD(&rcu_torture_removed);
 }
 
 static struct rcu_torture_ops rcu_sync_ops = {
         .init = rcu_sync_torture_init,
         .cleanup = NULL,
         .readlock = rcu_torture_read_lock,
         .readdelay = rcu_read_delay,
         .readunlock = rcu_torture_read_unlock,
         .completed = rcu_torture_completed,
         .deferredfree = rcu_sync_torture_deferred_free,
         .sync = synchronize_rcu,
         .cb_barrier = NULL,
         .stats = NULL,
         .irqcapable = 1,
         .name = "rcu_sync"
 };
 
 /*
  * Definitions for rcu_bh torture testing.
  */
 
 static int rcu_bh_torture_read_lock(void) __acquires(RCU_BH)
 {
         rcu_read_lock_bh();
         return 0;
 }
 
 static void rcu_bh_torture_read_unlock(int idx) __releases(RCU_BH)
 {
         rcu_read_unlock_bh();
 }
 
 static int rcu_bh_torture_completed(void)
 {
         return rcu_batches_completed_bh();
 }
 
 static void rcu_bh_torture_deferred_free(struct rcu_torture *p)
 {
         call_rcu_bh(&p->rtort_rcu, rcu_torture_cb);
 }
 
 struct rcu_bh_torture_synchronize {
         struct rcu_head head;
         struct completion completion;
 };
 
 static void rcu_bh_torture_wakeme_after_cb(struct rcu_head *head)
 {
         struct rcu_bh_torture_synchronize *rcu;
 
         rcu = container_of(head, struct rcu_bh_torture_synchronize, head);
         complete(&rcu->completion);
 }
 
 static void rcu_bh_torture_synchronize(void)
 {
         struct rcu_bh_torture_synchronize rcu;
 
         init_completion(&rcu.completion);
         call_rcu_bh(&rcu.head, rcu_bh_torture_wakeme_after_cb);
         wait_for_completion(&rcu.completion);
 }
 
 static struct rcu_torture_ops rcu_bh_ops = {
         .init = NULL,
         .cleanup = NULL,
         .readlock = rcu_bh_torture_read_lock,
         .readdelay = rcu_read_delay,  /* just reuse rcu's version. */
         .readunlock = rcu_bh_torture_read_unlock,
         .completed = rcu_bh_torture_completed,
         .deferredfree = rcu_bh_torture_deferred_free,
         .sync = rcu_bh_torture_synchronize,
         .cb_barrier = rcu_barrier_bh,
         .stats = NULL,
         .irqcapable = 1,
         .name = "rcu_bh"
 };
 
 static struct rcu_torture_ops rcu_bh_sync_ops = {
         .init = rcu_sync_torture_init,
         .cleanup = NULL,
         .readlock = rcu_bh_torture_read_lock,
         .readdelay = rcu_read_delay,  /* just reuse rcu's version. */
         .readunlock = rcu_bh_torture_read_unlock,
         .completed = rcu_bh_torture_completed,
         .deferredfree = rcu_sync_torture_deferred_free,
         .sync = rcu_bh_torture_synchronize,
         .cb_barrier = NULL,
         .stats = NULL,
         .irqcapable = 1,
         .name = "rcu_bh_sync"
 };
 
 /*
  * Definitions for srcu torture testing.
  */
 
 static struct srcu_struct srcu_ctl;
 
 static void srcu_torture_init(void)
 {
         init_srcu_struct(&srcu_ctl);
         rcu_sync_torture_init();
 }
 
 static void srcu_torture_cleanup(void)
 {
         synchronize_srcu(&srcu_ctl);
         cleanup_srcu_struct(&srcu_ctl);
 }
 
 static int srcu_torture_read_lock(void) __acquires(&srcu_ctl)
 {
         return srcu_read_lock(&srcu_ctl);
 }
 
 static void srcu_read_delay(struct rcu_random_state *rrsp)
 {
         long delay;
         const long uspertick = 1000000 / HZ;
         const long longdelay = 10;
 
         /* We want there to be long-running readers, but not all the time. */
 
         delay = rcu_random(rrsp) % (nrealreaders * 2 * longdelay * uspertick);
         if (!delay)
                 schedule_timeout_interruptible(longdelay);
 }
 
 static void srcu_torture_read_unlock(int idx) __releases(&srcu_ctl)
 {
         srcu_read_unlock(&srcu_ctl, idx);
 }
 
 static int srcu_torture_completed(void)
 {
         return srcu_batches_completed(&srcu_ctl);
 }
 
 static void srcu_torture_synchronize(void)
 {
         synchronize_srcu(&srcu_ctl);
 }
 
 static int srcu_torture_stats(char *page)
 {
         int cnt = 0;
         int cpu;
         int idx = srcu_ctl.completed & 0x1;
 
         cnt += sprintf(&page[cnt], "%s%s per-CPU(idx=%d):",
                        torture_type, TORTURE_FLAG, idx);
         for_each_possible_cpu(cpu) {
                 cnt += sprintf(&page[cnt], " %d(%d,%d)", cpu,
                                per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[!idx],
                                per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[idx]);
         }
         cnt += sprintf(&page[cnt], "\n");
         return cnt;
 }
 
 static struct rcu_torture_ops srcu_ops = {
         .init = srcu_torture_init,
         .cleanup = srcu_torture_cleanup,
         .readlock = srcu_torture_read_lock,
         .readdelay = srcu_read_delay,
         .readunlock = srcu_torture_read_unlock,
         .completed = srcu_torture_completed,
         .deferredfree = rcu_sync_torture_deferred_free,
         .sync = srcu_torture_synchronize,
         .cb_barrier = NULL,
         .stats = srcu_torture_stats,
         .name = "srcu"
 };
 
 /*
  * Definitions for sched torture testing.
  */
 
 static int sched_torture_read_lock(void)
 {
         preempt_disable();
         return 0;
 }
 
 static void sched_torture_read_unlock(int idx)
 {
         preempt_enable();
 }
 
 static int sched_torture_completed(void)
 {
         return 0;
 }
 
 static void rcu_sched_torture_deferred_free(struct rcu_torture *p)
 {
         call_rcu_sched(&p->rtort_rcu, rcu_torture_cb);
 }
 
 static void sched_torture_synchronize(void)
 {
         synchronize_sched();
 }
 
 static struct rcu_torture_ops sched_ops = {
         .init = rcu_sync_torture_init,
         .cleanup = NULL,
         .readlock = sched_torture_read_lock,
         .readdelay = rcu_read_delay,  /* just reuse rcu's version. */
         .readunlock = sched_torture_read_unlock,
         .completed = sched_torture_completed,
         .deferredfree = rcu_sched_torture_deferred_free,
         .sync = sched_torture_synchronize,
         .cb_barrier = rcu_barrier_sched,
         .stats = NULL,
         .irqcapable = 1,
         .name = "sched"
 };
 
 static struct rcu_torture_ops sched_ops_sync = {
         .init = rcu_sync_torture_init,
         .cleanup = NULL,
         .readlock = sched_torture_read_lock,
         .readdelay = rcu_read_delay,  /* just reuse rcu's version. */
         .readunlock = sched_torture_read_unlock,
         .completed = sched_torture_completed,
         .deferredfree = rcu_sync_torture_deferred_free,
         .sync = sched_torture_synchronize,
         .cb_barrier = NULL,
         .stats = NULL,
         .name = "sched_sync"
 };
 
 /*
  * RCU torture writer kthread.  Repeatedly substitutes a new structure
  * for that pointed to by rcu_torture_current, freeing the old structure
  * after a series of grace periods (the "pipeline").
  */
 static int
 rcu_torture_writer(void *arg)
 {
         int i;
         long oldbatch = rcu_batches_completed();
         struct rcu_torture *rp;
         struct rcu_torture *old_rp;
         static DEFINE_RCU_RANDOM(rand);
 
         VERBOSE_PRINTK_STRING("rcu_torture_writer task started");
         set_user_nice(current, 19);
 
         do {
                 schedule_timeout_uninterruptible(1);
                 if ((rp = rcu_torture_alloc()) == NULL)
                         continue;
                 rp->rtort_pipe_count = 0;
                 udelay(rcu_random(&rand) & 0x3ff);
                 old_rp = rcu_torture_current;
                 rp->rtort_mbtest = 1;
                 rcu_assign_pointer(rcu_torture_current, rp);
                 smp_wmb();
                 if (old_rp) {
                         i = old_rp->rtort_pipe_count;
                         if (i > RCU_TORTURE_PIPE_LEN)
                                 i = RCU_TORTURE_PIPE_LEN;
                         atomic_inc(&rcu_torture_wcount[i]);
                         old_rp->rtort_pipe_count++;
                         cur_ops->deferredfree(old_rp);
                 }
                 rcu_torture_current_version++;
                 oldbatch = cur_ops->completed();
                 rcu_stutter_wait();
         } while (!kthread_should_stop() && !fullstop);
         VERBOSE_PRINTK_STRING("rcu_torture_writer task stopping");
         while (!kthread_should_stop())
                 schedule_timeout_uninterruptible(1);
         return 0;
 }
 
 /*
  * RCU torture fake writer kthread.  Repeatedly calls sync, with a random
  * delay between calls.
  */
 static int
 rcu_torture_fakewriter(void *arg)
 {
         DEFINE_RCU_RANDOM(rand);
 
         VERBOSE_PRINTK_STRING("rcu_torture_fakewriter task started");
         set_user_nice(current, 19);
 
         do {
                 schedule_timeout_uninterruptible(1 + rcu_random(&rand)%10);
                 udelay(rcu_random(&rand) & 0x3ff);
                 cur_ops->sync();
                 rcu_stutter_wait();
         } while (!kthread_should_stop() && !fullstop);
 
         VERBOSE_PRINTK_STRING("rcu_torture_fakewriter task stopping");
         while (!kthread_should_stop())
                 schedule_timeout_uninterruptible(1);
         return 0;
 }
 
 /*
  * RCU torture reader from timer handler.  Dereferences rcu_torture_current,
  * incrementing the corresponding element of the pipeline array.  The
  * counter in the element should never be greater than 1, otherwise, the
  * RCU implementation is broken.
  */
 static void rcu_torture_timer(unsigned long unused)
 {
         int idx;
         int completed;
         static DEFINE_RCU_RANDOM(rand);
         static DEFINE_SPINLOCK(rand_lock);
         struct rcu_torture *p;
         int pipe_count;
 
         idx = cur_ops->readlock();
         completed = cur_ops->completed();
         p = rcu_dereference(rcu_torture_current);
         if (p == NULL) {
                 /* Leave because rcu_torture_writer is not yet underway */
                 cur_ops->readunlock(idx);
                 return;
         }
         if (p->rtort_mbtest == 0)
                 atomic_inc(&n_rcu_torture_mberror);
         spin_lock(&rand_lock);
         cur_ops->readdelay(&rand);
         n_rcu_torture_timers++;
         spin_unlock(&rand_lock);
         preempt_disable();
         pipe_count = p->rtort_pipe_count;
         if (pipe_count > RCU_TORTURE_PIPE_LEN) {
                 /* Should not happen, but... */
                 pipe_count = RCU_TORTURE_PIPE_LEN;
         }
         ++__get_cpu_var(rcu_torture_count)[pipe_count];
         completed = cur_ops->completed() - completed;
         if (completed > RCU_TORTURE_PIPE_LEN) {
                 /* Should not happen, but... */
                 completed = RCU_TORTURE_PIPE_LEN;
         }
         ++__get_cpu_var(rcu_torture_batch)[completed];
         preempt_enable();
         cur_ops->readunlock(idx);
 }
 
 /*
  * RCU torture reader kthread.  Repeatedly dereferences rcu_torture_current,
  * incrementing the corresponding element of the pipeline array.  The
  * counter in the element should never be greater than 1, otherwise, the
  * RCU implementation is broken.
  */
 static int
 rcu_torture_reader(void *arg)
 {
         int completed;
         int idx;
         DEFINE_RCU_RANDOM(rand);
         struct rcu_torture *p;
         int pipe_count;
         struct timer_list t;
 
         VERBOSE_PRINTK_STRING("rcu_torture_reader task started");
         set_user_nice(current, 19);
         if (irqreader && cur_ops->irqcapable)
                 setup_timer_on_stack(&t, rcu_torture_timer, 0);
 
         do {
                 if (irqreader && cur_ops->irqcapable) {
                         if (!timer_pending(&t))
                                 mod_timer(&t, 1);
                 }
                 idx = cur_ops->readlock();
                 completed = cur_ops->completed();
                 p = rcu_dereference(rcu_torture_current);
                 if (p == NULL) {
                         /* Wait for rcu_torture_writer to get underway */
                         cur_ops->readunlock(idx);
                         schedule_timeout_interruptible(HZ);
                         continue;
                 }
                 if (p->rtort_mbtest == 0)
                         atomic_inc(&n_rcu_torture_mberror);
                 cur_ops->readdelay(&rand);
                 preempt_disable();
                 pipe_count = p->rtort_pipe_count;
                 if (pipe_count > RCU_TORTURE_PIPE_LEN) {
                         /* Should not happen, but... */
                         pipe_count = RCU_TORTURE_PIPE_LEN;
                 }
                 ++__get_cpu_var(rcu_torture_count)[pipe_count];
                 completed = cur_ops->completed() - completed;
                 if (completed > RCU_TORTURE_PIPE_LEN) {
                         /* Should not happen, but... */
                         completed = RCU_TORTURE_PIPE_LEN;
                 }
                 ++__get_cpu_var(rcu_torture_batch)[completed];
                 preempt_enable();
                 cur_ops->readunlock(idx);
                 schedule();
                 rcu_stutter_wait();
         } while (!kthread_should_stop() && !fullstop);
         VERBOSE_PRINTK_STRING("rcu_torture_reader task stopping");
         if (irqreader && cur_ops->irqcapable)
                 del_timer_sync(&t);
         while (!kthread_should_stop())
                 schedule_timeout_uninterruptible(1);
         return 0;
 }
 
 /*
  * Create an RCU-torture statistics message in the specified buffer.
  */
 static int
 rcu_torture_printk(char *page)
 {
         int cnt = 0;
         int cpu;
         int i;
         long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
         long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
 
         for_each_possible_cpu(cpu) {
                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
                         pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i];
                         batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i];
                 }
         }
         for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
                 if (pipesummary[i] != 0)
                         break;
         }
         cnt += sprintf(&page[cnt], "%s%s ", torture_type, TORTURE_FLAG);
         cnt += sprintf(&page[cnt],
                        "rtc: %p ver: %ld tfle: %d rta: %d rtaf: %d rtf: %d "
                        "rtmbe: %d nt: %ld",
                        rcu_torture_current,
                        rcu_torture_current_version,
                        list_empty(&rcu_torture_freelist),
                        atomic_read(&n_rcu_torture_alloc),
                        atomic_read(&n_rcu_torture_alloc_fail),
                        atomic_read(&n_rcu_torture_free),
                        atomic_read(&n_rcu_torture_mberror),
                        n_rcu_torture_timers);
         if (atomic_read(&n_rcu_torture_mberror) != 0)
                 cnt += sprintf(&page[cnt], " !!!");
         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
         if (i > 1) {
                 cnt += sprintf(&page[cnt], "!!! ");
                 atomic_inc(&n_rcu_torture_error);
                 WARN_ON_ONCE(1);
         }
         cnt += sprintf(&page[cnt], "Reader Pipe: ");
         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
                 cnt += sprintf(&page[cnt], " %ld", pipesummary[i]);
         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
         cnt += sprintf(&page[cnt], "Reader Batch: ");
         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
                 cnt += sprintf(&page[cnt], " %ld", batchsummary[i]);
         cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG);
         cnt += sprintf(&page[cnt], "Free-Block Circulation: ");
         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
                 cnt += sprintf(&page[cnt], " %d",
                                atomic_read(&rcu_torture_wcount[i]));
         }
         cnt += sprintf(&page[cnt], "\n");
         if (cur_ops->stats)
                 cnt += cur_ops->stats(&page[cnt]);
         return cnt;
 }
 
 /*
  * 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 rcu_torture_stats
  * kthread full control (or the init/cleanup functions when rcu_torture_stats
  * thread is not running).
  */
 static void
 rcu_torture_stats_print(void)
 {
         int cnt;
 
         cnt = rcu_torture_printk(printk_buf);
         printk(KERN_ALERT "%s", printk_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
 rcu_torture_stats(void *arg)
 {
         VERBOSE_PRINTK_STRING("rcu_torture_stats task started");
         do {
                 schedule_timeout_interruptible(stat_interval * HZ);
                 rcu_torture_stats_print();
         } while (!kthread_should_stop());
         VERBOSE_PRINTK_STRING("rcu_torture_stats task stopping");
         return 0;
 }
 
 static int rcu_idle_cpu;        /* Force all torture tasks off this CPU */
 
 /* Shuffle tasks such that we allow @rcu_idle_cpu to become idle. A special case
  * is when @rcu_idle_cpu = -1, when we allow the tasks to run on all CPUs.
  */
 static void rcu_torture_shuffle_tasks(void)
 {
         cpumask_t tmp_mask;
         int i;
 
         cpus_setall(tmp_mask);
         get_online_cpus();
 
         /* No point in shuffling if there is only one online CPU (ex: UP) */
         if (num_online_cpus() == 1) {
                 put_online_cpus();
                 return;
         }
 
         if (rcu_idle_cpu != -1)
                 cpu_clear(rcu_idle_cpu, tmp_mask);
 
         set_cpus_allowed_ptr(current, &tmp_mask);
 
         if (reader_tasks) {
                 for (i = 0; i < nrealreaders; i++)
                         if (reader_tasks[i])
                                 set_cpus_allowed_ptr(reader_tasks[i],
                                                      &tmp_mask);
         }
 
         if (fakewriter_tasks) {
                 for (i = 0; i < nfakewriters; i++)
                         if (fakewriter_tasks[i])
                                 set_cpus_allowed_ptr(fakewriter_tasks[i],
                                                      &tmp_mask);
         }
 
         if (writer_task)
                 set_cpus_allowed_ptr(writer_task, &tmp_mask);
 
         if (stats_task)
                 set_cpus_allowed_ptr(stats_task, &tmp_mask);
 
         if (rcu_idle_cpu == -1)
                 rcu_idle_cpu = num_online_cpus() - 1;
         else
                 rcu_idle_cpu--;
 
         put_online_cpus();
 }
 
 /* Shuffle tasks across CPUs, with the intent of allowing each CPU in the
  * system to become idle at a time and cut off its timer ticks. This is meant
  * to test the support for such tickless idle CPU in RCU.
  */
 static int
 rcu_torture_shuffle(void *arg)
 {
         VERBOSE_PRINTK_STRING("rcu_torture_shuffle task started");
         do {
                 schedule_timeout_interruptible(shuffle_interval * HZ);
                 rcu_torture_shuffle_tasks();
         } while (!kthread_should_stop());
         VERBOSE_PRINTK_STRING("rcu_torture_shuffle task stopping");
         return 0;
 }
 
 /* Cause the rcutorture test to "stutter", starting and stopping all
  * threads periodically.
  */
 static int
 rcu_torture_stutter(void *arg)
 {
         VERBOSE_PRINTK_STRING("rcu_torture_stutter task started");
         do {
                 schedule_timeout_interruptible(stutter * HZ);
                 stutter_pause_test = 1;
                 if (!kthread_should_stop())
                         schedule_timeout_interruptible(stutter * HZ);
                 stutter_pause_test = 0;
         } while (!kthread_should_stop());
         VERBOSE_PRINTK_STRING("rcu_torture_stutter task stopping");
         return 0;
 }
 
 static inline void
 rcu_torture_print_module_parms(char *tag)
 {
         printk(KERN_ALERT "%s" TORTURE_FLAG
                 "--- %s: nreaders=%d nfakewriters=%d "
                 "stat_interval=%d verbose=%d test_no_idle_hz=%d "
                 "shuffle_interval=%d stutter=%d irqreader=%d\n",
                 torture_type, tag, nrealreaders, nfakewriters,
                 stat_interval, verbose, test_no_idle_hz, shuffle_interval,
                 stutter, irqreader);
 }
 
 static void
 rcu_torture_cleanup(void)
 {
         int i;
 
         fullstop = 1;
         if (stutter_task) {
                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_stutter task");
                 kthread_stop(stutter_task);
         }
         stutter_task = NULL;
         if (shuffler_task) {
                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_shuffle task");
                 kthread_stop(shuffler_task);
         }
         shuffler_task = NULL;
 
         if (writer_task) {
                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_writer task");
                 kthread_stop(writer_task);
         }
         writer_task = NULL;
 
         if (reader_tasks) {
                 for (i = 0; i < nrealreaders; i++) {
                         if (reader_tasks[i]) {
                                 VERBOSE_PRINTK_STRING(
                                         "Stopping rcu_torture_reader task");
                                 kthread_stop(reader_tasks[i]);
                         }
                         reader_tasks[i] = NULL;
                 }
                 kfree(reader_tasks);
                 reader_tasks = NULL;
         }
         rcu_torture_current = NULL;
 
         if (fakewriter_tasks) {
                 for (i = 0; i < nfakewriters; i++) {
                         if (fakewriter_tasks[i]) {
                                 VERBOSE_PRINTK_STRING(
                                         "Stopping rcu_torture_fakewriter task");
                                 kthread_stop(fakewriter_tasks[i]);
                         }
                         fakewriter_tasks[i] = NULL;
                 }
                 kfree(fakewriter_tasks);
                 fakewriter_tasks = NULL;
         }
 
         if (stats_task) {
                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_stats task");
                 kthread_stop(stats_task);
         }
         stats_task = NULL;
 
         /* Wait for all RCU callbacks to fire.  */
 
         if (cur_ops->cb_barrier != NULL)
                 cur_ops->cb_barrier();
 
         rcu_torture_stats_print();  /* -After- the stats thread is stopped! */
 
        if (cur_ops->cleanup)
                cur_ops->cleanup();
        if (atomic_read(&n_rcu_torture_error))
                rcu_torture_print_module_parms("End of test: FAILURE");
        else
                rcu_torture_print_module_parms("End of test: SUCCESS");
}

static int __init
rcu_torture_init(void)
{
        int i;
        int cpu;
        int firsterr = 0;
        static struct rcu_torture_ops *torture_ops[] =
                { &rcu_ops, &rcu_sync_ops, &rcu_bh_ops, &rcu_bh_sync_ops,
                  &srcu_ops, &sched_ops, &sched_ops_sync, };

        /* Process args and tell the world that the torturer is on the job. */
        for (i = 0; i < ARRAY_SIZE(torture_ops); i++) {
                cur_ops = torture_ops[i];
                if (strcmp(torture_type, cur_ops->name) == 0)
                        break;
        }
        if (i == ARRAY_SIZE(torture_ops)) {
                printk(KERN_ALERT "rcutorture: invalid torture type: \"%s\"\n",
                       torture_type);
                return (-EINVAL);
        }
        if (cur_ops->init)
                cur_ops->init(); /* no "goto unwind" prior to this point!!! */

        if (nreaders >= 0)
                nrealreaders = nreaders;
        else
                nrealreaders = 2 * num_online_cpus();
        rcu_torture_print_module_parms("Start of test");
        fullstop = 0;

        /* Set up the freelist. */

        INIT_LIST_HEAD(&rcu_torture_freelist);
        for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++) {
                rcu_tortures[i].rtort_mbtest = 0;
                list_add_tail(&rcu_tortures[i].rtort_free,
                              &rcu_torture_freelist);
        }

        /* Initialize the statistics so that each run gets its own numbers. */

        rcu_torture_current = NULL;
        rcu_torture_current_version = 0;
        atomic_set(&n_rcu_torture_alloc, 0);
        atomic_set(&n_rcu_torture_alloc_fail, 0);
        atomic_set(&n_rcu_torture_free, 0);
        atomic_set(&n_rcu_torture_mberror, 0);
        atomic_set(&n_rcu_torture_error, 0);
        for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
                atomic_set(&rcu_torture_wcount[i], 0);
        for_each_possible_cpu(cpu) {
                for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
                        per_cpu(rcu_torture_count, cpu)[i] = 0;
                        per_cpu(rcu_torture_batch, cpu)[i] = 0;
                }
        }

        /* Start up the kthreads. */

        VERBOSE_PRINTK_STRING("Creating rcu_torture_writer task");
        writer_task = kthread_run(rcu_torture_writer, NULL,
                                  "rcu_torture_writer");
        if (IS_ERR(writer_task)) {
                firsterr = PTR_ERR(writer_task);
                VERBOSE_PRINTK_ERRSTRING("Failed to create writer");
                writer_task = NULL;
                goto unwind;
        }
        fakewriter_tasks = kzalloc(nfakewriters * sizeof(fakewriter_tasks[0]),
                                   GFP_KERNEL);
        if (fakewriter_tasks == NULL) {
                VERBOSE_PRINTK_ERRSTRING("out of memory");
                firsterr = -ENOMEM;
                goto unwind;
        }
        for (i = 0; i < nfakewriters; i++) {
                VERBOSE_PRINTK_STRING("Creating rcu_torture_fakewriter task");
                fakewriter_tasks[i] = kthread_run(rcu_torture_fakewriter, NULL,
                                                  "rcu_torture_fakewriter");
                if (IS_ERR(fakewriter_tasks[i])) {
                        firsterr = PTR_ERR(fakewriter_tasks[i]);
                        VERBOSE_PRINTK_ERRSTRING("Failed to create fakewriter");
                        fakewriter_tasks[i] = NULL;
                        goto unwind;
                }
        }
        reader_tasks = kzalloc(nrealreaders * sizeof(reader_tasks[0]),
                               GFP_KERNEL);
        if (reader_tasks == NULL) {
                VERBOSE_PRINTK_ERRSTRING("out of memory");
                firsterr = -ENOMEM;
                goto unwind;
        }
        for (i = 0; i < nrealreaders; i++) {
                VERBOSE_PRINTK_STRING("Creating rcu_torture_reader task");
                reader_tasks[i] = kthread_run(rcu_torture_reader, NULL,
                                              "rcu_torture_reader");
                if (IS_ERR(reader_tasks[i])) {
                        firsterr = PTR_ERR(reader_tasks[i]);
                        VERBOSE_PRINTK_ERRSTRING("Failed to create reader");
                        reader_tasks[i] = NULL;
                        goto unwind;
                }
        }
        if (stat_interval > 0) {
                VERBOSE_PRINTK_STRING("Creating rcu_torture_stats task");
                stats_task = kthread_run(rcu_torture_stats, NULL,
                                        "rcu_torture_stats");
                if (IS_ERR(stats_task)) {
                        firsterr = PTR_ERR(stats_task);
                        VERBOSE_PRINTK_ERRSTRING("Failed to create stats");
                        stats_task = NULL;
                        goto unwind;
                }
        }
        if (test_no_idle_hz) {
                rcu_idle_cpu = num_online_cpus() - 1;
                /* Create the shuffler thread */
                shuffler_task = kthread_run(rcu_torture_shuffle, NULL,
                                          "rcu_torture_shuffle");
                if (IS_ERR(shuffler_task)) {
                        firsterr = PTR_ERR(shuffler_task);
                        VERBOSE_PRINTK_ERRSTRING("Failed to create shuffler");
                        shuffler_task = NULL;
                        goto unwind;
                }
        }
        if (stutter < 0)
                stutter = 0;
        if (stutter) {
                /* Create the stutter thread */
                stutter_task = kthread_run(rcu_torture_stutter, NULL,
                                          "rcu_torture_stutter");
                if (IS_ERR(stutter_task)) {
                        firsterr = PTR_ERR(stutter_task);
                        VERBOSE_PRINTK_ERRSTRING("Failed to create stutter");
                        stutter_task = NULL;
                        goto unwind;
                }
        }
        return 0;

unwind:
        rcu_torture_cleanup();
        return firsterr;
}

module_init(rcu_torture_init);
module_exit(rcu_torture_cleanup);