Merge branch 'perf/urgent' into perf/core
[linux-2.6.git] / kernel / rcutorture.c
index 6e2f0a8..9bb5217 100644 (file)
@@ -18,7 +18,7 @@
  * Copyright (C) IBM Corporation, 2005, 2006
  *
  * Authors: Paul E. McKenney <paulmck@us.ibm.com>
- *          Josh Triplett <josh@freedesktop.org>
+ *       Josh Triplett <josh@freedesktop.org>
  *
  * See also:  Documentation/RCU/torture.txt
  */
 #include <linux/sched.h>
 #include <asm/atomic.h>
 #include <linux/bitops.h>
-#include <linux/module.h>
 #include <linux/completion.h>
 #include <linux/moduleparam.h>
 #include <linux/percpu.h>
 #include <linux/notifier.h>
+#include <linux/reboot.h>
+#include <linux/freezer.h>
 #include <linux/cpu.h>
-#include <linux/random.h>
 #include <linux/delay.h>
-#include <linux/byteorder/swabb.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>");
+             "Josh Triplett <josh@freedesktop.org>");
 
 static int nreaders = -1;      /* # reader threads, defaults to 2*ncpus */
 static int nfakewriters = 4;   /* # fake writer threads */
@@ -57,22 +58,28 @@ 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 = 5; /* Interval between shuffles (in sec)*/
-static char *torture_type = "rcu"; /* What to torture: rcu, rcu_bh, srcu. */
+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, 0);
+module_param(nreaders, int, 0444);
 MODULE_PARM_DESC(nreaders, "Number of RCU reader threads");
-module_param(nfakewriters, int, 0);
+module_param(nfakewriters, int, 0444);
 MODULE_PARM_DESC(nfakewriters, "Number of RCU fake writer threads");
-module_param(stat_interval, int, 0);
+module_param(stat_interval, int, 0444);
 MODULE_PARM_DESC(stat_interval, "Number of seconds between stats printk()s");
-module_param(verbose, bool, 0);
+module_param(verbose, bool, 0444);
 MODULE_PARM_DESC(verbose, "Enable verbose debugging printk()s");
-module_param(test_no_idle_hz, bool, 0);
+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, 0);
+module_param(shuffle_interval, int, 0444);
 MODULE_PARM_DESC(shuffle_interval, "Number of seconds between shuffles");
-module_param(torture_type, charp, 0);
+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:"
@@ -91,6 +98,7 @@ 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
 
@@ -101,10 +109,9 @@ struct rcu_torture {
        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_torture_current;
+static long rcu_torture_current_version;
 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) =
@@ -117,7 +124,58 @@ 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;
 static struct list_head rcu_torture_removed;
+static cpumask_var_t shuffle_tmp_mask;
+
+static int stutter_pause_test;
+
+#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;
+
+/* Mediate rmmod and system shutdown.  Concurrent rmmod & shutdown illegal! */
+
+#define FULLSTOP_DONTSTOP 0    /* Normal operation. */
+#define FULLSTOP_SHUTDOWN 1    /* System shutdown with rcutorture running. */
+#define FULLSTOP_RMMOD    2    /* Normal rmmod of rcutorture. */
+static int fullstop = FULLSTOP_RMMOD;
+DEFINE_MUTEX(fullstop_mutex);  /* Protect fullstop transitions and spawning */
+                               /*  of kthreads. */
+
+/*
+ * Detect and respond to a system shutdown.
+ */
+static int
+rcutorture_shutdown_notify(struct notifier_block *unused1,
+                          unsigned long unused2, void *unused3)
+{
+       mutex_lock(&fullstop_mutex);
+       if (fullstop == FULLSTOP_DONTSTOP)
+               fullstop = FULLSTOP_SHUTDOWN;
+       else
+               printk(KERN_WARNING /* but going down anyway, so... */
+                      "Concurrent 'rmmod rcutorture' and shutdown illegal!\n");
+       mutex_unlock(&fullstop_mutex);
+       return NOTIFY_DONE;
+}
+
+/*
+ * Absorb kthreads into a kernel function that won't return, so that
+ * they won't ever access module text or data again.
+ */
+static void rcutorture_shutdown_absorb(char *title)
+{
+       if (ACCESS_ONCE(fullstop) == FULLSTOP_SHUTDOWN) {
+               printk(KERN_NOTICE
+                      "rcutorture thread %s parking due to system shutdown\n",
+                      title);
+               schedule_timeout_uninterruptible(MAX_SCHEDULE_TIMEOUT);
+       }
+}
 
 /*
  * Allocate an element from the rcu_tortures pool.
@@ -165,22 +223,32 @@ struct rcu_random_state {
 
 /*
  * Crude but fast random-number generator.  Uses a linear congruential
- * generator, with occasional help from get_random_bytes().
+ * generator, with occasional help from cpu_clock().
  */
 static unsigned long
 rcu_random(struct rcu_random_state *rrsp)
 {
-       long refresh;
-
        if (--rrsp->rrs_count < 0) {
-               get_random_bytes(&refresh, sizeof(refresh));
-               rrsp->rrs_state += refresh;
+               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(char *title)
+{
+       while (stutter_pause_test || !rcutorture_runnable) {
+               if (rcutorture_runnable)
+                       schedule_timeout_interruptible(1);
+               else
+                       schedule_timeout_interruptible(round_jiffies_relative(HZ));
+               rcutorture_shutdown_absorb(title);
+       }
+}
+
 /*
  * Operations vector for selecting different types of tests.
  */
@@ -189,15 +257,18 @@ struct rcu_torture_ops {
        void (*init)(void);
        void (*cleanup)(void);
        int (*readlock)(void);
-       void (*readdelay)(struct rcu_random_state *rrsp);
+       void (*read_delay)(struct rcu_random_state *rrsp);
        void (*readunlock)(int idx);
        int (*completed)(void);
-       void (*deferredfree)(struct rcu_torture *p);
+       void (*deferred_free)(struct rcu_torture *p);
        void (*sync)(void);
+       void (*cb_barrier)(void);
        int (*stats)(char *page);
+       int irq_capable;
        char *name;
 };
-static struct rcu_torture_ops *cur_ops = NULL;
+
+static struct rcu_torture_ops *cur_ops;
 
 /*
  * Definitions for rcu torture testing.
@@ -211,14 +282,17 @@ static int rcu_torture_read_lock(void) __acquires(RCU)
 
 static void rcu_read_delay(struct rcu_random_state *rrsp)
 {
-       long delay;
-       const long longdelay = 200;
+       const unsigned long shortdelay_us = 200;
+       const unsigned long longdelay_ms = 50;
 
-       /* We want there to be long-running readers, but not all the time. */
+       /* We want a short delay sometimes to make a reader delay the grace
+        * period, and we want a long delay occasionally to trigger
+        * force_quiescent_state. */
 
-       delay = rcu_random(rrsp) % (nrealreaders * 2 * longdelay);
-       if (!delay)
-               udelay(longdelay);
+       if (!(rcu_random(rrsp) % (nrealreaders * 2000 * longdelay_ms)))
+               mdelay(longdelay_ms);
+       if (!(rcu_random(rrsp) % (nrealreaders * 2 * shortdelay_us)))
+               udelay(shortdelay_us);
 }
 
 static void rcu_torture_read_unlock(int idx) __releases(RCU)
@@ -237,7 +311,7 @@ rcu_torture_cb(struct rcu_head *p)
        int i;
        struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu);
 
-       if (fullstop) {
+       if (fullstop != FULLSTOP_DONTSTOP) {
                /* Test is ending, just drop callbacks on the floor. */
                /* The next initialization will pick up the pieces. */
                return;
@@ -250,7 +324,12 @@ rcu_torture_cb(struct rcu_head *p)
                rp->rtort_mbtest = 0;
                rcu_torture_free(rp);
        } else
-               cur_ops->deferredfree(rp);
+               cur_ops->deferred_free(rp);
+}
+
+static int rcu_no_completed(void)
+{
+       return 0;
 }
 
 static void rcu_torture_deferred_free(struct rcu_torture *p)
@@ -259,16 +338,18 @@ static void rcu_torture_deferred_free(struct rcu_torture *p)
 }
 
 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,
-       .stats = NULL,
-       .name = "rcu"
+       .init           = NULL,
+       .cleanup        = NULL,
+       .readlock       = rcu_torture_read_lock,
+       .read_delay     = rcu_read_delay,
+       .readunlock     = rcu_torture_read_unlock,
+       .completed      = rcu_torture_completed,
+       .deferred_free  = rcu_torture_deferred_free,
+       .sync           = synchronize_rcu,
+       .cb_barrier     = rcu_barrier,
+       .stats          = NULL,
+       .irq_capable    = 1,
+       .name           = "rcu"
 };
 
 static void rcu_sync_torture_deferred_free(struct rcu_torture *p)
@@ -297,6 +378,36 @@ 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,
+       .read_delay     = rcu_read_delay,
+       .readunlock     = rcu_torture_read_unlock,
+       .completed      = rcu_torture_completed,
+       .deferred_free  = rcu_sync_torture_deferred_free,
+       .sync           = synchronize_rcu,
+       .cb_barrier     = NULL,
+       .stats          = NULL,
+       .irq_capable    = 1,
+       .name           = "rcu_sync"
+};
+
+static struct rcu_torture_ops rcu_expedited_ops = {
+       .init           = rcu_sync_torture_init,
+       .cleanup        = NULL,
+       .readlock       = rcu_torture_read_lock,
+       .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
+       .readunlock     = rcu_torture_read_unlock,
+       .completed      = rcu_no_completed,
+       .deferred_free  = rcu_sync_torture_deferred_free,
+       .sync           = synchronize_rcu_expedited,
+       .cb_barrier     = NULL,
+       .stats          = NULL,
+       .irq_capable    = 1,
+       .name           = "rcu_expedited"
+};
+
 /*
  * Definitions for rcu_bh torture testing.
  */
@@ -345,16 +456,33 @@ static void rcu_bh_torture_synchronize(void)
 }
 
 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,
-       .stats = NULL,
-       .name = "rcu_bh"
+       .init           = NULL,
+       .cleanup        = NULL,
+       .readlock       = rcu_bh_torture_read_lock,
+       .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
+       .readunlock     = rcu_bh_torture_read_unlock,
+       .completed      = rcu_bh_torture_completed,
+       .deferred_free  = rcu_bh_torture_deferred_free,
+       .sync           = rcu_bh_torture_synchronize,
+       .cb_barrier     = rcu_barrier_bh,
+       .stats          = NULL,
+       .irq_capable    = 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,
+       .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
+       .readunlock     = rcu_bh_torture_read_unlock,
+       .completed      = rcu_bh_torture_completed,
+       .deferred_free  = rcu_sync_torture_deferred_free,
+       .sync           = rcu_bh_torture_synchronize,
+       .cb_barrier     = NULL,
+       .stats          = NULL,
+       .irq_capable    = 1,
+       .name           = "rcu_bh_sync"
 };
 
 /*
@@ -375,7 +503,7 @@ static void srcu_torture_cleanup(void)
        cleanup_srcu_struct(&srcu_ctl);
 }
 
-static int srcu_torture_read_lock(void)
+static int srcu_torture_read_lock(void) __acquires(&srcu_ctl)
 {
        return srcu_read_lock(&srcu_ctl);
 }
@@ -393,7 +521,7 @@ static void srcu_read_delay(struct rcu_random_state *rrsp)
                schedule_timeout_interruptible(longdelay);
 }
 
-static void srcu_torture_read_unlock(int idx)
+static void srcu_torture_read_unlock(int idx) __releases(&srcu_ctl)
 {
        srcu_read_unlock(&srcu_ctl, idx);
 }
@@ -426,20 +554,106 @@ static int srcu_torture_stats(char *page)
 }
 
 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,
-       .stats = srcu_torture_stats,
-       .name = "srcu"
+       .init           = srcu_torture_init,
+       .cleanup        = srcu_torture_cleanup,
+       .readlock       = srcu_torture_read_lock,
+       .read_delay     = srcu_read_delay,
+       .readunlock     = srcu_torture_read_unlock,
+       .completed      = srcu_torture_completed,
+       .deferred_free  = rcu_sync_torture_deferred_free,
+       .sync           = srcu_torture_synchronize,
+       .cb_barrier     = NULL,
+       .stats          = srcu_torture_stats,
+       .name           = "srcu"
 };
 
-static struct rcu_torture_ops *torture_ops[] =
-       { &rcu_ops, &rcu_bh_ops, &srcu_ops, NULL };
+static void srcu_torture_synchronize_expedited(void)
+{
+       synchronize_srcu_expedited(&srcu_ctl);
+}
+
+static struct rcu_torture_ops srcu_expedited_ops = {
+       .init           = srcu_torture_init,
+       .cleanup        = srcu_torture_cleanup,
+       .readlock       = srcu_torture_read_lock,
+       .read_delay     = srcu_read_delay,
+       .readunlock     = srcu_torture_read_unlock,
+       .completed      = srcu_torture_completed,
+       .deferred_free  = rcu_sync_torture_deferred_free,
+       .sync           = srcu_torture_synchronize_expedited,
+       .cb_barrier     = NULL,
+       .stats          = srcu_torture_stats,
+       .name           = "srcu_expedited"
+};
+
+/*
+ * 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 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,
+       .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
+       .readunlock     = sched_torture_read_unlock,
+       .completed      = rcu_no_completed,
+       .deferred_free  = rcu_sched_torture_deferred_free,
+       .sync           = sched_torture_synchronize,
+       .cb_barrier     = rcu_barrier_sched,
+       .stats          = NULL,
+       .irq_capable    = 1,
+       .name           = "sched"
+};
+
+static struct rcu_torture_ops sched_sync_ops = {
+       .init           = rcu_sync_torture_init,
+       .cleanup        = NULL,
+       .readlock       = sched_torture_read_lock,
+       .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
+       .readunlock     = sched_torture_read_unlock,
+       .completed      = rcu_no_completed,
+       .deferred_free  = rcu_sync_torture_deferred_free,
+       .sync           = sched_torture_synchronize,
+       .cb_barrier     = NULL,
+       .stats          = NULL,
+       .name           = "sched_sync"
+};
+
+static struct rcu_torture_ops sched_expedited_ops = {
+       .init           = rcu_sync_torture_init,
+       .cleanup        = NULL,
+       .readlock       = sched_torture_read_lock,
+       .read_delay     = rcu_read_delay,  /* just reuse rcu's version. */
+       .readunlock     = sched_torture_read_unlock,
+       .completed      = rcu_no_completed,
+       .deferred_free  = rcu_sync_torture_deferred_free,
+       .sync           = synchronize_sched_expedited,
+       .cb_barrier     = NULL,
+       .stats          = rcu_expedited_torture_stats,
+       .irq_capable    = 1,
+       .name           = "sched_expedited"
+};
 
 /*
  * RCU torture writer kthread.  Repeatedly substitutes a new structure
@@ -460,26 +674,29 @@ rcu_torture_writer(void *arg)
 
        do {
                schedule_timeout_uninterruptible(1);
-               if ((rp = rcu_torture_alloc()) == NULL)
+               rp = rcu_torture_alloc();
+               if (rp == 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 != NULL) {
+               smp_wmb(); /* Mods to old_rp must follow rcu_assign_pointer() */
+               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);
+                       cur_ops->deferred_free(old_rp);
                }
                rcu_torture_current_version++;
                oldbatch = cur_ops->completed();
-       } while (!kthread_should_stop() && !fullstop);
+               rcu_stutter_wait("rcu_torture_writer");
+       } while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
        VERBOSE_PRINTK_STRING("rcu_torture_writer task stopping");
+       rcutorture_shutdown_absorb("rcu_torture_writer");
        while (!kthread_should_stop())
                schedule_timeout_uninterruptible(1);
        return 0;
@@ -501,15 +718,63 @@ rcu_torture_fakewriter(void *arg)
                schedule_timeout_uninterruptible(1 + rcu_random(&rand)%10);
                udelay(rcu_random(&rand) & 0x3ff);
                cur_ops->sync();
-       } while (!kthread_should_stop() && !fullstop);
+               rcu_stutter_wait("rcu_torture_fakewriter");
+       } while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
 
        VERBOSE_PRINTK_STRING("rcu_torture_fakewriter task stopping");
+       rcutorture_shutdown_absorb("rcu_torture_fakewriter");
        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->read_delay(&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;
+       }
+       __this_cpu_inc(per_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;
+       }
+       __this_cpu_inc(per_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
@@ -523,11 +788,18 @@ rcu_torture_reader(void *arg)
        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->irq_capable)
+               setup_timer_on_stack(&t, rcu_torture_timer, 0);
 
        do {
+               if (irqreader && cur_ops->irq_capable) {
+                       if (!timer_pending(&t))
+                               mod_timer(&t, 1);
+               }
                idx = cur_ops->readlock();
                completed = cur_ops->completed();
                p = rcu_dereference(rcu_torture_current);
@@ -539,25 +811,29 @@ rcu_torture_reader(void *arg)
                }
                if (p->rtort_mbtest == 0)
                        atomic_inc(&n_rcu_torture_mberror);
-               cur_ops->readdelay(&rand);
+               cur_ops->read_delay(&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];
+               __this_cpu_inc(per_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];
+               __this_cpu_inc(per_cpu_var(rcu_torture_batch)[completed]);
                preempt_enable();
                cur_ops->readunlock(idx);
                schedule();
-       } while (!kthread_should_stop() && !fullstop);
+               rcu_stutter_wait("rcu_torture_reader");
+       } while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);
        VERBOSE_PRINTK_STRING("rcu_torture_reader task stopping");
+       rcutorture_shutdown_absorb("rcu_torture_reader");
+       if (irqreader && cur_ops->irq_capable)
+               del_timer_sync(&t);
        while (!kthread_should_stop())
                schedule_timeout_uninterruptible(1);
        return 0;
@@ -588,20 +864,22 @@ rcu_torture_printk(char *page)
        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",
+                      "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));
+                      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++)
@@ -617,7 +895,7 @@ rcu_torture_printk(char *page)
                               atomic_read(&rcu_torture_wcount[i]));
        }
        cnt += sprintf(&page[cnt], "\n");
-       if (cur_ops->stats != NULL)
+       if (cur_ops->stats)
                cnt += cur_ops->stats(&page[cnt]);
        return cnt;
 }
@@ -653,6 +931,7 @@ rcu_torture_stats(void *arg)
        do {
                schedule_timeout_interruptible(stat_interval * HZ);
                rcu_torture_stats_print();
+               rcutorture_shutdown_absorb("rcu_torture_stats");
        } while (!kthread_should_stop());
        VERBOSE_PRINTK_STRING("rcu_torture_stats task stopping");
        return 0;
@@ -665,46 +944,48 @@ static int rcu_idle_cpu;  /* Force all torture tasks off this CPU */
  */
 static void rcu_torture_shuffle_tasks(void)
 {
-       cpumask_t tmp_mask = CPU_MASK_ALL;
        int i;
 
-       lock_cpu_hotplug();
+       cpumask_setall(shuffle_tmp_mask);
+       get_online_cpus();
 
        /* No point in shuffling if there is only one online CPU (ex: UP) */
        if (num_online_cpus() == 1) {
-               unlock_cpu_hotplug();
+               put_online_cpus();
                return;
        }
 
        if (rcu_idle_cpu != -1)
-               cpu_clear(rcu_idle_cpu, tmp_mask);
+               cpumask_clear_cpu(rcu_idle_cpu, shuffle_tmp_mask);
 
-       set_cpus_allowed(current, tmp_mask);
+       set_cpus_allowed_ptr(current, shuffle_tmp_mask);
 
-       if (reader_tasks != NULL) {
+       if (reader_tasks) {
                for (i = 0; i < nrealreaders; i++)
                        if (reader_tasks[i])
-                               set_cpus_allowed(reader_tasks[i], tmp_mask);
+                               set_cpus_allowed_ptr(reader_tasks[i],
+                                                    shuffle_tmp_mask);
        }
 
-       if (fakewriter_tasks != NULL) {
+       if (fakewriter_tasks) {
                for (i = 0; i < nfakewriters; i++)
                        if (fakewriter_tasks[i])
-                               set_cpus_allowed(fakewriter_tasks[i], tmp_mask);
+                               set_cpus_allowed_ptr(fakewriter_tasks[i],
+                                                    shuffle_tmp_mask);
        }
 
        if (writer_task)
-               set_cpus_allowed(writer_task, tmp_mask);
+               set_cpus_allowed_ptr(writer_task, shuffle_tmp_mask);
 
        if (stats_task)
-               set_cpus_allowed(stats_task, tmp_mask);
+               set_cpus_allowed_ptr(stats_task, shuffle_tmp_mask);
 
        if (rcu_idle_cpu == -1)
                rcu_idle_cpu = num_online_cpus() - 1;
        else
                rcu_idle_cpu--;
 
-       unlock_cpu_hotplug();
+       put_online_cpus();
 }
 
 /* Shuffle tasks across CPUs, with the intent of allowing each CPU in the
@@ -718,43 +999,86 @@ rcu_torture_shuffle(void *arg)
        do {
                schedule_timeout_interruptible(shuffle_interval * HZ);
                rcu_torture_shuffle_tasks();
+               rcutorture_shutdown_absorb("rcu_torture_shuffle");
        } 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;
+               rcutorture_shutdown_absorb("rcu_torture_stutter");
+       } 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\n",
+               "shuffle_interval=%d stutter=%d irqreader=%d\n",
                torture_type, tag, nrealreaders, nfakewriters,
-               stat_interval, verbose, test_no_idle_hz, shuffle_interval);
+               stat_interval, verbose, test_no_idle_hz, shuffle_interval,
+               stutter, irqreader);
 }
 
+static struct notifier_block rcutorture_nb = {
+       .notifier_call = rcutorture_shutdown_notify,
+};
+
 static void
 rcu_torture_cleanup(void)
 {
        int i;
 
-       fullstop = 1;
-       if (shuffler_task != NULL) {
+       mutex_lock(&fullstop_mutex);
+       if (fullstop == FULLSTOP_SHUTDOWN) {
+               printk(KERN_WARNING /* but going down anyway, so... */
+                      "Concurrent 'rmmod rcutorture' and shutdown illegal!\n");
+               mutex_unlock(&fullstop_mutex);
+               schedule_timeout_uninterruptible(10);
+               if (cur_ops->cb_barrier != NULL)
+                       cur_ops->cb_barrier();
+               return;
+       }
+       fullstop = FULLSTOP_RMMOD;
+       mutex_unlock(&fullstop_mutex);
+       unregister_reboot_notifier(&rcutorture_nb);
+       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);
+               free_cpumask_var(shuffle_tmp_mask);
        }
        shuffler_task = NULL;
 
-       if (writer_task != NULL) {
+       if (writer_task) {
                VERBOSE_PRINTK_STRING("Stopping rcu_torture_writer task");
                kthread_stop(writer_task);
        }
        writer_task = NULL;
 
-       if (reader_tasks != NULL) {
+       if (reader_tasks) {
                for (i = 0; i < nrealreaders; i++) {
-                       if (reader_tasks[i] != NULL) {
+                       if (reader_tasks[i]) {
                                VERBOSE_PRINTK_STRING(
                                        "Stopping rcu_torture_reader task");
                                kthread_stop(reader_tasks[i]);
@@ -766,9 +1090,9 @@ rcu_torture_cleanup(void)
        }
        rcu_torture_current = NULL;
 
-       if (fakewriter_tasks != NULL) {
+       if (fakewriter_tasks) {
                for (i = 0; i < nfakewriters; i++) {
-                       if (fakewriter_tasks[i] != NULL) {
+                       if (fakewriter_tasks[i]) {
                                VERBOSE_PRINTK_STRING(
                                        "Stopping rcu_torture_fakewriter task");
                                kthread_stop(fakewriter_tasks[i]);
@@ -779,18 +1103,20 @@ rcu_torture_cleanup(void)
                fakewriter_tasks = NULL;
        }
 
-       if (stats_task != 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.  */
-       rcu_barrier();
+
+       if (cur_ops->cb_barrier != NULL)
+               cur_ops->cb_barrier();
 
        rcu_torture_stats_print();  /* -After- the stats thread is stopped! */
 
-       if (cur_ops->cleanup != NULL)
+       if (cur_ops->cleanup)
                cur_ops->cleanup();
        if (atomic_read(&n_rcu_torture_error))
                rcu_torture_print_module_parms("End of test: FAILURE");
@@ -798,27 +1124,37 @@ rcu_torture_cleanup(void)
                rcu_torture_print_module_parms("End of test: SUCCESS");
 }
 
-static int
+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_expedited_ops,
+                 &rcu_bh_ops, &rcu_bh_sync_ops,
+                 &srcu_ops, &srcu_expedited_ops,
+                 &sched_ops, &sched_sync_ops, &sched_expedited_ops, };
 
-       /* Process args and tell the world that the torturer is on the job. */
+       mutex_lock(&fullstop_mutex);
 
-       for (i = 0; cur_ops = torture_ops[i], cur_ops != NULL; i++) {
+       /* 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) {
+               if (strcmp(torture_type, cur_ops->name) == 0)
                        break;
-               }
        }
-       if (cur_ops == NULL) {
-               printk(KERN_ALERT "rcutorture: invalid torture type: \"%s\"\n",
+       if (i == ARRAY_SIZE(torture_ops)) {
+               printk(KERN_ALERT "rcu-torture: invalid torture type: \"%s\"\n",
                       torture_type);
-               return (-EINVAL);
+               printk(KERN_ALERT "rcu-torture types:");
+               for (i = 0; i < ARRAY_SIZE(torture_ops); i++)
+                       printk(KERN_ALERT " %s", torture_ops[i]->name);
+               printk(KERN_ALERT "\n");
+               mutex_unlock(&fullstop_mutex);
+               return -EINVAL;
        }
-       if (cur_ops->init != NULL)
+       if (cur_ops->init)
                cur_ops->init(); /* no "goto unwind" prior to this point!!! */
 
        if (nreaders >= 0)
@@ -826,12 +1162,12 @@ rcu_torture_init(void)
        else
                nrealreaders = 2 * num_online_cpus();
        rcu_torture_print_module_parms("Start of test");
-       fullstop = 0;
+       fullstop = FULLSTOP_DONTSTOP;
 
        /* Set up the freelist. */
 
        INIT_LIST_HEAD(&rcu_torture_freelist);
-       for (i = 0; i < sizeof(rcu_tortures) / sizeof(rcu_tortures[0]); i++) {
+       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);
@@ -867,7 +1203,7 @@ rcu_torture_init(void)
                goto unwind;
        }
        fakewriter_tasks = kzalloc(nfakewriters * sizeof(fakewriter_tasks[0]),
-                                  GFP_KERNEL);
+                                  GFP_KERNEL);
        if (fakewriter_tasks == NULL) {
                VERBOSE_PRINTK_ERRSTRING("out of memory");
                firsterr = -ENOMEM;
@@ -876,7 +1212,7 @@ rcu_torture_init(void)
        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");
+                                                 "rcu_torture_fakewriter");
                if (IS_ERR(fakewriter_tasks[i])) {
                        firsterr = PTR_ERR(fakewriter_tasks[i]);
                        VERBOSE_PRINTK_ERRSTRING("Failed to create fakewriter");
@@ -915,19 +1251,43 @@ rcu_torture_init(void)
        }
        if (test_no_idle_hz) {
                rcu_idle_cpu = num_online_cpus() - 1;
+
+               if (!alloc_cpumask_var(&shuffle_tmp_mask, GFP_KERNEL)) {
+                       firsterr = -ENOMEM;
+                       VERBOSE_PRINTK_ERRSTRING("Failed to alloc mask");
+                       goto unwind;
+               }
+
                /* Create the shuffler thread */
                shuffler_task = kthread_run(rcu_torture_shuffle, NULL,
                                          "rcu_torture_shuffle");
                if (IS_ERR(shuffler_task)) {
+                       free_cpumask_var(shuffle_tmp_mask);
                        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;
+               }
+       }
+       register_reboot_notifier(&rcutorture_nb);
+       mutex_unlock(&fullstop_mutex);
        return 0;
 
 unwind:
+       mutex_unlock(&fullstop_mutex);
        rcu_torture_cleanup();
        return firsterr;
 }