2 files changed, 168 insertions, 24 deletions

diff --git a/Documentation/locking/locktorture.txt b/Documentation/locking/locktorture.txt
index f2a905b27862..7a72621b924f 100644
--- a/Documentation/locking/locktorture.txt
+++ b/Documentation/locking/locktorture.txt
@@ -29,6 +29,11 @@ nwriters_stress   Number of kernel threads that will stress exclusive lock
                   ownership (writers). The default value is twice the number
                   of online CPUs.
 
+nreaders_stress   Number of kernel threads that will stress shared lock
+                  ownership (readers). The default is the same amount of writer
+                  locks. If the user did not specify nwriters_stress, then
+                  both readers and writers be the amount of online CPUs.
+
 torture_type      Type of lock to torture. By default, only spinlocks will
                   be tortured. This module can torture the following locks,
                   with string values as follows:
@@ -97,15 +102,18 @@ STATISTICS
 Statistics are printed in the following format:
 
 spin_lock-torture: Writes:  Total: 93746064  Max/Min: 0/0   Fail: 0
-   (A)                             (B)            (C)          (D)
+   (A)              (B)            (C)            (D)          (E)
 
 (A): Lock type that is being tortured -- torture_type parameter.
 
-(B): Number of times the lock was acquired.
+(B): Number of writer lock acquisitions. If dealing with a read/write primitive
+     a second "Reads" statistics line is printed.
+
+(C): Number of times the lock was acquired.
 
-(C): Min and max number of times threads failed to acquire the lock.
+(D): Min and max number of times threads failed to acquire the lock.
 
-(D): true/false values if there were errors acquiring the lock. This should
+(E): true/false values if there were errors acquiring the lock. This should
      -only- be positive if there is a bug in the locking primitive's
      implementation. Otherwise a lock should never fail (i.e., spin_lock()).
      Of course, the same applies for (C), above. A dummy example of this is
diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
index 988267cc92c1..c1073d79e440 100644
--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -52,6 +52,8 @@ 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");
@@ -74,15 +76,19 @@ static atomic_t n_lock_torture_errors;
 
 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 int nrealreaders_stress;
+static bool lock_is_read_held;
 
 struct lock_stress_stats {
         long n_lock_fail;
         long n_lock_acquired;
 };
 static struct lock_stress_stats *lwsa; /* writer statistics */
+static struct lock_stress_stats *lrsa; /* reader statistics */
 
 #if defined(MODULE)
 #define LOCKTORTURE_RUNNABLE_INIT 1
@@ -104,6 +110,9 @@ 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;
 };
@@ -142,6 +151,9 @@ 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"
 };
 
@@ -182,6 +194,9 @@ 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"
 };
 
@@ -205,6 +220,9 @@ 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"
 };
 
@@ -241,6 +259,9 @@ 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"
 };
 
@@ -274,28 +295,57 @@ static int lock_torture_writer(void *arg)
 }
 
 /*
+ * 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);
+                cur_ops->readlock();
+                lock_is_read_held = 1;
+                lrsp->n_lock_acquired++;
+                cur_ops->read_delay(&rand);
+                lock_is_read_held = 0;
+                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_lock_acquired;
+        long min = statp[0].n_lock_acquired;
         long long sum = 0;
 
-        for (i = 0; i < nrealwriters_stress; i++) {
-                if (lwsa[i].n_lock_fail)
+        n_stress = write ? nrealwriters_stress : nrealreaders_stress;
+        for (i = 0; i < n_stress; i++) {
+                if (statp[i].n_lock_fail)
                         fail = true;
-                sum += lwsa[i].n_lock_acquired;
-                if (max < lwsa[i].n_lock_fail)
-                        max = lwsa[i].n_lock_fail;
-                if (min > lwsa[i].n_lock_fail)
-                        min = lwsa[i].n_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)
@@ -315,15 +365,32 @@ static void lock_torture_stats_print(void)
         int size = nrealwriters_stress * 200 + 8192;
         char *buf;
 
+        if (cur_ops->readlock)
+                size += 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, lwsa, true);
         pr_alert("%s", buf);
         kfree(buf);
+
+        if (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, lrsa, false);
+                pr_alert("%s", buf);
+                kfree(buf);
+        }
 }
 
 /*
@@ -350,10 +417,10 @@ lock_torture_print_module_parms(struct lock_torture_ops *cur_ops,
                                 const char *tag)
 {
         pr_alert("%s" TORTURE_FLAG
-                 "--- %s%s: nwriters_stress=%d stat_interval=%d verbose=%d shuffle_interval=%d stutter=%d shutdown_secs=%d onoff_interval=%d onoff_holdoff=%d\n",
+                 "--- %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, debug_lock ? " [debug]": "",
-                 nrealwriters_stress, stat_interval, verbose,
-                 shuffle_interval, stutter, shutdown_secs,
+                 nrealwriters_stress, nrealreaders_stress, stat_interval,
+                 verbose, shuffle_interval, stutter, shutdown_secs,
                  onoff_interval, onoff_holdoff);
 }
 
@@ -372,6 +439,14 @@ static void lock_torture_cleanup(void)
                 writer_tasks = NULL;
         }
 
+        if (reader_tasks) {
+                for (i = 0; i < 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! */
 
@@ -389,7 +464,7 @@ static void lock_torture_cleanup(void)
 
 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, &mutex_lock_ops,
@@ -430,7 +505,6 @@ static int __init lock_torture_init(void)
         if (strncmp(torture_type, "spin", 4) == 0)
                 debug_lock = true;
 #endif
-        lock_torture_print_module_parms(cur_ops, "Start of test");
 
         /* Initialize the statistics so that each run gets its own numbers. */
 
@@ -446,8 +520,37 @@ static int __init lock_torture_init(void)
                 lwsa[i].n_lock_acquired = 0;
         }
 
-        /* Start up the kthreads. */
+        if (cur_ops->readlock) {
+                if (nreaders_stress >= 0)
+                        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 */
+                                nrealwriters_stress = num_online_cpus();
+                        nrealreaders_stress = nrealwriters_stress;
+                }
+
+                lock_is_read_held = 0;
+                lrsa = kmalloc(sizeof(*lrsa) * nrealreaders_stress, GFP_KERNEL);
+                if (lrsa == NULL) {
+                        VERBOSE_TOROUT_STRING("lrsa: Out of memory");
+                        firsterr = -ENOMEM;
+                        kfree(lwsa);
+                        goto unwind;
+                }
 
+                for (i = 0; i < nrealreaders_stress; i++) {
+                        lrsa[i].n_lock_fail = 0;
+                        lrsa[i].n_lock_acquired = 0;
+                }
+        }
+        lock_torture_print_module_parms(cur_ops, "Start of test");
+
+        /* Prepare torture context. */
         if (onoff_interval > 0) {
                 firsterr = torture_onoff_init(onoff_holdoff * HZ,
                                               onoff_interval * HZ);
@@ -478,11 +581,44 @@ static int __init lock_torture_init(void)
                 firsterr = -ENOMEM;
                 goto unwind;
         }
-        for (i = 0; i < nrealwriters_stress; i++) {
+
+        if (cur_ops->readlock) {
+                reader_tasks = kzalloc(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 < nrealwriters_stress ||
+                    j < nrealreaders_stress; i++, j++) {
+                if (i >= nrealwriters_stress)
+                        goto create_reader;
+
+                /* Create writer. */
                 firsterr = torture_create_kthread(lock_torture_writer, &lwsa[i],
                                                   writer_tasks[i]);
                 if (firsterr)
                         goto unwind;
+
+        create_reader:
+                if (cur_ops->readlock == NULL || (j >= nrealreaders_stress))
+                        continue;
+                /* Create reader. */
+                firsterr = torture_create_kthread(lock_torture_reader, &lrsa[j],
+                                                  reader_tasks[j]);
+                if (firsterr)
+                        goto unwind;
         }
         if (stat_interval > 0) {
                 firsterr = torture_create_kthread(lock_torture_stats, NULL,