Merge tag 'upstream-3.18-rc1-v2' of git://git.infradead.org/linux-ubifs
[firefly-linux-kernel-4.4.55.git] / kernel / locking / locktorture.c
index 0955b885d0dc8eb5fe54aeeebe08c0eee6bd9cb7..ec8cce259779061dd863e6a48ff1dcfa1a7a131c 100644 (file)
  * Author: Paul E. McKenney <paulmck@us.ibm.com>
  *     Based on kernel/rcu/torture.c.
  */
-#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/rwlock.h>
+#include <linux/mutex.h>
+#include <linux/rwsem.h>
 #include <linux/smp.h>
 #include <linux/interrupt.h>
 #include <linux/sched.h>
 #include <linux/atomic.h>
-#include <linux/bitops.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/delay.h>
-#include <linux/stat.h>
 #include <linux/slab.h>
-#include <linux/trace_clock.h>
-#include <asm/byteorder.h>
 #include <linux/torture.h>
 
 MODULE_LICENSE("GPL");
@@ -51,6 +41,8 @@ MODULE_AUTHOR("Paul E. McKenney <paulmck@us.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");
@@ -66,30 +58,28 @@ torture_param(bool, verbose, true,
 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, ...)");
-
-static atomic_t n_lock_torture_errors;
+                "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 int nrealwriters_stress;
 static bool lock_is_write_held;
+static bool lock_is_read_held;
 
-struct lock_writer_stress_stats {
-       long n_write_lock_fail;
-       long n_write_lock_acquired;
+struct lock_stress_stats {
+       long n_lock_fail;
+       long n_lock_acquired;
 };
-static struct lock_writer_stress_stats *lwsa;
 
 #if defined(MODULE)
 #define LOCKTORTURE_RUNNABLE_INIT 1
 #else
 #define LOCKTORTURE_RUNNABLE_INIT 0
 #endif
-int locktorture_runnable = LOCKTORTURE_RUNNABLE_INIT;
-module_param(locktorture_runnable, int, 0444);
-MODULE_PARM_DESC(locktorture_runnable, "Start locktorture at module init");
+int torture_runnable = LOCKTORTURE_RUNNABLE_INIT;
+module_param(torture_runnable, int, 0444);
+MODULE_PARM_DESC(torture_runnable, "Start locktorture at module init");
 
 /* Forward reference. */
 static void lock_torture_cleanup(void);
@@ -102,12 +92,25 @@ struct lock_torture_ops {
        int (*writelock)(void);
        void (*write_delay)(struct torture_random_state *trsp);
        void (*writeunlock)(void);
+       int (*readlock)(void);
+       void (*read_delay)(struct torture_random_state *trsp);
+       void (*readunlock)(void);
        unsigned long flags;
        const char *name;
 };
 
-static struct lock_torture_ops *cur_ops;
-
+struct lock_torture_cxt {
+       int nrealwriters_stress;
+       int nrealreaders_stress;
+       bool debug_lock;
+       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,
+                                      ATOMIC_INIT(0),
+                                      NULL, NULL};
 /*
  * Definitions for lock torture testing.
  */
@@ -123,10 +126,10 @@ static void torture_lock_busted_write_delay(struct torture_random_state *trsp)
 
        /* We want a long delay occasionally to force massive contention.  */
        if (!(torture_random(trsp) %
-             (nrealwriters_stress * 2000 * longdelay_us)))
+             (cxt.nrealwriters_stress * 2000 * longdelay_us)))
                mdelay(longdelay_us);
 #ifdef CONFIG_PREEMPT
-       if (!(torture_random(trsp) % (nrealwriters_stress * 20000)))
+       if (!(torture_random(trsp) % (cxt.nrealwriters_stress * 20000)))
                preempt_schedule();  /* Allow test to be preempted. */
 #endif
 }
@@ -140,6 +143,9 @@ static struct lock_torture_ops lock_busted_ops = {
        .writelock      = torture_lock_busted_write_lock,
        .write_delay    = torture_lock_busted_write_delay,
        .writeunlock    = torture_lock_busted_write_unlock,
+       .readlock       = NULL,
+       .read_delay     = NULL,
+       .readunlock     = NULL,
        .name           = "lock_busted"
 };
 
@@ -160,13 +166,13 @@ static void torture_spin_lock_write_delay(struct torture_random_state *trsp)
         * we want a long delay occasionally to force massive contention.
         */
        if (!(torture_random(trsp) %
-             (nrealwriters_stress * 2000 * longdelay_us)))
+             (cxt.nrealwriters_stress * 2000 * longdelay_us)))
                mdelay(longdelay_us);
        if (!(torture_random(trsp) %
-             (nrealwriters_stress * 2 * shortdelay_us)))
+             (cxt.nrealwriters_stress * 2 * shortdelay_us)))
                udelay(shortdelay_us);
 #ifdef CONFIG_PREEMPT
-       if (!(torture_random(trsp) % (nrealwriters_stress * 20000)))
+       if (!(torture_random(trsp) % (cxt.nrealwriters_stress * 20000)))
                preempt_schedule();  /* Allow test to be preempted. */
 #endif
 }
@@ -180,39 +186,253 @@ static struct lock_torture_ops spin_lock_ops = {
        .writelock      = torture_spin_lock_write_lock,
        .write_delay    = torture_spin_lock_write_delay,
        .writeunlock    = torture_spin_lock_write_unlock,
+       .readlock       = NULL,
+       .read_delay     = NULL,
+       .readunlock     = NULL,
        .name           = "spin_lock"
 };
 
 static int torture_spin_lock_write_lock_irq(void)
-__acquires(torture_spinlock_irq)
+__acquires(torture_spinlock)
 {
        unsigned long flags;
 
        spin_lock_irqsave(&torture_spinlock, flags);
-       cur_ops->flags = flags;
+       cxt.cur_ops->flags = flags;
        return 0;
 }
 
 static void torture_lock_spin_write_unlock_irq(void)
 __releases(torture_spinlock)
 {
-       spin_unlock_irqrestore(&torture_spinlock, cur_ops->flags);
+       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,
        .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(void) __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(void) __releases(torture_rwlock)
+{
+       write_unlock(&torture_rwlock);
+}
+
+static int torture_rwlock_read_lock(void) __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(void) __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,
+       .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(void) __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(void)
+__releases(torture_rwlock)
+{
+       write_unlock_irqrestore(&torture_rwlock, cxt.cur_ops->flags);
+}
+
+static int torture_rwlock_read_lock_irq(void) __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(void)
+__releases(torture_rwlock)
+{
+       write_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,
+       .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(void) __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);
+#ifdef CONFIG_PREEMPT
+       if (!(torture_random(trsp) % (cxt.nrealwriters_stress * 20000)))
+               preempt_schedule();  /* Allow test to be preempted. */
+#endif
+}
+
+static void torture_mutex_unlock(void) __releases(torture_mutex)
+{
+       mutex_unlock(&torture_mutex);
+}
+
+static struct lock_torture_ops mutex_lock_ops = {
+       .writelock      = torture_mutex_lock,
+       .write_delay    = torture_mutex_delay,
+       .writeunlock    = torture_mutex_unlock,
+       .readlock       = NULL,
+       .read_delay     = NULL,
+       .readunlock     = NULL,
+       .name           = "mutex_lock"
+};
+
+static DECLARE_RWSEM(torture_rwsem);
+static int torture_rwsem_down_write(void) __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);
+#ifdef CONFIG_PREEMPT
+       if (!(torture_random(trsp) % (cxt.nrealwriters_stress * 20000)))
+               preempt_schedule();  /* Allow test to be preempted. */
+#endif
+}
+
+static void torture_rwsem_up_write(void) __releases(torture_rwsem)
+{
+       up_write(&torture_rwsem);
+}
+
+static int torture_rwsem_down_read(void) __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.nrealwriters_stress * 2000 * longdelay_ms)))
+               mdelay(longdelay_ms * 2);
+       else
+               mdelay(longdelay_ms / 2);
+#ifdef CONFIG_PREEMPT
+       if (!(torture_random(trsp) % (cxt.nrealreaders_stress * 20000)))
+               preempt_schedule();  /* Allow test to be preempted. */
+#endif
+}
+
+static void torture_rwsem_up_read(void) __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,
+       .writeunlock    = torture_rwsem_up_write,
+       .readlock       = torture_rwsem_down_read,
+       .read_delay     = torture_rwsem_read_delay,
+       .readunlock     = torture_rwsem_up_read,
+       .name           = "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_writer_stress_stats *lwsp = arg;
+       struct lock_stress_stats *lwsp = arg;
        static DEFINE_TORTURE_RANDOM(rand);
 
        VERBOSE_TOROUT_STRING("lock_torture_writer task started");
@@ -221,47 +441,86 @@ static int lock_torture_writer(void *arg)
        do {
                if ((torture_random(&rand) & 0xfffff) == 0)
                        schedule_timeout_uninterruptible(1);
-               cur_ops->writelock();
+
+               cxt.cur_ops->writelock();
                if (WARN_ON_ONCE(lock_is_write_held))
-                       lwsp->n_write_lock_fail++;
+                       lwsp->n_lock_fail++;
                lock_is_write_held = 1;
-               lwsp->n_write_lock_acquired++;
-               cur_ops->write_delay(&rand);
+               if (WARN_ON_ONCE(lock_is_read_held))
+                       lwsp->n_lock_fail++; /* rare, but... */
+
+               lwsp->n_lock_acquired++;
+               cxt.cur_ops->write_delay(&rand);
                lock_is_write_held = 0;
-               cur_ops->writeunlock();
+               cxt.cur_ops->writeunlock();
+
                stutter_wait("lock_torture_writer");
        } while (!torture_must_stop());
        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;
+       static 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();
+               lock_is_read_held = 1;
+               if (WARN_ON_ONCE(lock_is_write_held))
+                       lrsp->n_lock_fail++; /* rare, but... */
+
+               lrsp->n_lock_acquired++;
+               cxt.cur_ops->read_delay(&rand);
+               lock_is_read_held = 0;
+               cxt.cur_ops->readunlock();
+
+               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 lock_torture_printk(char *page)
+static void __torture_print_stats(char *page,
+                                 struct lock_stress_stats *statp, bool write)
 {
        bool fail = 0;
-       int i;
+       int i, n_stress;
        long max = 0;
-       long min = lwsa[0].n_write_lock_acquired;
+       long min = statp[0].n_lock_acquired;
        long long sum = 0;
 
-       for (i = 0; i < nrealwriters_stress; i++) {
-               if (lwsa[i].n_write_lock_fail)
+       n_stress = write ? cxt.nrealwriters_stress : cxt.nrealreaders_stress;
+       for (i = 0; i < n_stress; i++) {
+               if (statp[i].n_lock_fail)
                        fail = true;
-               sum += lwsa[i].n_write_lock_acquired;
-               if (max < lwsa[i].n_write_lock_fail)
-                       max = lwsa[i].n_write_lock_fail;
-               if (min > lwsa[i].n_write_lock_fail)
-                       min = lwsa[i].n_write_lock_fail;
+               sum += statp[i].n_lock_acquired;
+               if (max < statp[i].n_lock_fail)
+                       max = statp[i].n_lock_fail;
+               if (min > statp[i].n_lock_fail)
+                       min = statp[i].n_lock_fail;
        }
-       page += sprintf(page, "%s%s ", torture_type, TORTURE_FLAG);
        page += sprintf(page,
-                       "Writes:  Total: %lld  Max/Min: %ld/%ld %s  Fail: %d %s\n",
+                       "%s:  Total: %lld  Max/Min: %ld/%ld %s  Fail: %d %s\n",
+                       write ? "Writes" : "Reads ",
                        sum, max, min, max / 2 > min ? "???" : "",
                        fail, fail ? "!!!" : "");
        if (fail)
-               atomic_inc(&n_lock_torture_errors);
+               atomic_inc(&cxt.n_lock_torture_errors);
 }
 
 /*
@@ -274,18 +533,35 @@ static void lock_torture_printk(char *page)
  */
 static void lock_torture_stats_print(void)
 {
-       int size = nrealwriters_stress * 200 + 8192;
+       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;
        }
-       lock_torture_printk(buf);
+
+       __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);
+       }
 }
 
 /*
@@ -312,9 +588,10 @@ lock_torture_print_module_parms(struct lock_torture_ops *cur_ops,
                                const char *tag)
 {
        pr_alert("%s" TORTURE_FLAG
-                "--- %s: nwriters_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, nrealwriters_stress, stat_interval, verbose,
-                shuffle_interval, stutter, shutdown_secs,
+                "--- %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);
 }
 
@@ -322,46 +599,59 @@ static void lock_torture_cleanup(void)
 {
        int i;
 
-       if (torture_cleanup())
+       if (torture_cleanup_begin())
                return;
 
        if (writer_tasks) {
-               for (i = 0; i < nrealwriters_stress; i++)
+               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(&n_lock_torture_errors))
-               lock_torture_print_module_parms(cur_ops,
+       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(cur_ops,
+               lock_torture_print_module_parms(cxt.cur_ops,
                                                "End of test: LOCK_HOTPLUG");
        else
-               lock_torture_print_module_parms(cur_ops,
+               lock_torture_print_module_parms(cxt.cur_ops,
                                                "End of test: SUCCESS");
+       torture_cleanup_end();
 }
 
 static int __init lock_torture_init(void)
 {
-       int i;
+       int i, j;
        int firsterr = 0;
        static struct lock_torture_ops *torture_ops[] = {
-               &lock_busted_ops, &spin_lock_ops, &spin_lock_irq_ops,
+               &lock_busted_ops,
+               &spin_lock_ops, &spin_lock_irq_ops,
+               &rw_lock_ops, &rw_lock_irq_ops,
+               &mutex_lock_ops,
+               &rwsem_lock_ops,
        };
 
-       if (!torture_init_begin(torture_type, verbose, &locktorture_runnable))
+       if (!torture_init_begin(torture_type, verbose, &torture_runnable))
                return -EBUSY;
 
        /* 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)
+               cxt.cur_ops = torture_ops[i];
+               if (strcmp(torture_type, cxt.cur_ops->name) == 0)
                        break;
        }
        if (i == ARRAY_SIZE(torture_ops)) {
@@ -374,31 +664,69 @@ static int __init lock_torture_init(void)
                torture_init_end();
                return -EINVAL;
        }
-       if (cur_ops->init)
-               cur_ops->init(); /* no "goto unwind" prior to this point!!! */
+       if (cxt.cur_ops->init)
+               cxt.cur_ops->init(); /* no "goto unwind" prior to this point!!! */
 
        if (nwriters_stress >= 0)
-               nrealwriters_stress = nwriters_stress;
+               cxt.nrealwriters_stress = nwriters_stress;
        else
-               nrealwriters_stress = 2 * num_online_cpus();
-       lock_torture_print_module_parms(cur_ops, "Start of test");
+               cxt.nrealwriters_stress = 2 * num_online_cpus();
+
+#ifdef CONFIG_DEBUG_MUTEXES
+       if (strncmp(torture_type, "mutex", 5) == 0)
+               cxt.debug_lock = true;
+#endif
+#ifdef CONFIG_DEBUG_SPINLOCK
+       if ((strncmp(torture_type, "spin", 4) == 0) ||
+           (strncmp(torture_type, "rw_lock", 7) == 0))
+               cxt.debug_lock = true;
+#endif
 
        /* Initialize the statistics so that each run gets its own numbers. */
 
        lock_is_write_held = 0;
-       lwsa = kmalloc(sizeof(*lwsa) * nrealwriters_stress, GFP_KERNEL);
-       if (lwsa == NULL) {
-               VERBOSE_TOROUT_STRING("lwsa: Out of memory");
+       cxt.lwsa = kmalloc(sizeof(*cxt.lwsa) * cxt.nrealwriters_stress, GFP_KERNEL);
+       if (cxt.lwsa == NULL) {
+               VERBOSE_TOROUT_STRING("cxt.lwsa: Out of memory");
                firsterr = -ENOMEM;
                goto unwind;
        }
-       for (i = 0; i < nrealwriters_stress; i++) {
-               lwsa[i].n_write_lock_fail = 0;
-               lwsa[i].n_write_lock_acquired = 0;
+       for (i = 0; i < cxt.nrealwriters_stress; i++) {
+               cxt.lwsa[i].n_lock_fail = 0;
+               cxt.lwsa[i].n_lock_acquired = 0;
        }
 
-       /* Start up the kthreads. */
+       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;
+               }
+
+               lock_is_read_held = 0;
+               cxt.lrsa = kmalloc(sizeof(*cxt.lrsa) * cxt.nrealreaders_stress, GFP_KERNEL);
+               if (cxt.lrsa == NULL) {
+                       VERBOSE_TOROUT_STRING("cxt.lrsa: Out of memory");
+                       firsterr = -ENOMEM;
+                       kfree(cxt.lwsa);
+                       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);
@@ -422,18 +750,51 @@ static int __init lock_torture_init(void)
                        goto unwind;
        }
 
-       writer_tasks = kzalloc(nrealwriters_stress * sizeof(writer_tasks[0]),
+       writer_tasks = kzalloc(cxt.nrealwriters_stress * sizeof(writer_tasks[0]),
                               GFP_KERNEL);
        if (writer_tasks == NULL) {
                VERBOSE_TOROUT_ERRSTRING("writer_tasks: Out of memory");
                firsterr = -ENOMEM;
                goto unwind;
        }
-       for (i = 0; i < nrealwriters_stress; i++) {
-               firsterr = torture_create_kthread(lock_torture_writer, &lwsa[i],
+
+       if (cxt.cur_ops->readlock) {
+               reader_tasks = kzalloc(cxt.nrealreaders_stress * sizeof(reader_tasks[0]),
+                                      GFP_KERNEL);
+               if (reader_tasks == NULL) {
+                       VERBOSE_TOROUT_ERRSTRING("reader_tasks: Out of memory");
+                       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 (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 (firsterr)
+                       goto unwind;
        }
        if (stat_interval > 0) {
                firsterr = torture_create_kthread(lock_torture_stats, NULL,