locktorture: Support rwlocks

Add a "rw_lock" torture test to stress kernel rwlocks and their irq
variant. Reader critical regions are 5x longer than writers. As such
a similar ratio of lock acquisitions is seen in the statistics. In the
case of massive contention, both hold the lock for 1/10 of a second.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

5 files changed, 125 insertions, 3 deletions

diff --git a/Documentation/locking/locktorture.txt b/Documentation/locking/locktorture.txt
index be715015e0f7..619f2bb136a5 100644
--- a/Documentation/locking/locktorture.txt
+++ b/Documentation/locking/locktorture.txt
@@ -45,6 +45,11 @@ torture_type	  Type of lock to torture. By default, only spinlocks will
                      o "spin_lock_irq": spin_lock_irq() and spin_unlock_irq()
                                         pairs.
 
+                     o "rw_lock": read/write lock() and unlock() rwlock pairs.
+
+                     o "rw_lock_irq": read/write lock_irq() and unlock_irq()
+                                      rwlock pairs.
+
                      o "mutex_lock": mutex_lock() and mutex_unlock() pairs.
 
                      o "rwsem_lock": read/write down() and up() semaphore pairs.
diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
index 540d5dfe1112..0762b25b4110 100644
--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -27,6 +27,7 @@
 #include <linux/kthread.h>
 #include <linux/err.h>
 #include <linux/spinlock.h>
+#include <linux/rwlock.h>
 #include <linux/mutex.h>
 #include <linux/smp.h>
 #include <linux/interrupt.h>
@@ -229,6 +230,110 @@ static struct lock_torture_ops spin_lock_irq_ops = {
         .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)
@@ -535,8 +640,11 @@ static int __init lock_torture_init(void)
         int i, j;
         int firsterr = 0;
         static struct lock_torture_ops *torture_ops[] = {
-                &lock_busted_ops, &spin_lock_ops, &spin_lock_irq_ops,
-                &mutex_lock_ops, &rwsem_lock_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, &torture_runnable))
@@ -571,7 +679,8 @@ static int __init lock_torture_init(void)
                 cxt.debug_lock = true;
 #endif
 #ifdef CONFIG_DEBUG_SPINLOCK
-        if (strncmp(torture_type, "spin", 4) == 0)
+        if ((strncmp(torture_type, "spin", 4) == 0) ||
+            (strncmp(torture_type, "rw_lock", 7) == 0))
                 cxt.debug_lock = true;
 #endif
 
diff --git a/tools/testing/selftests/rcutorture/configs/lock/CFLIST b/tools/testing/selftests/rcutorture/configs/lock/CFLIST
index 6108137da770..6910b7370761 100644
--- a/tools/testing/selftests/rcutorture/configs/lock/CFLIST
+++ b/tools/testing/selftests/rcutorture/configs/lock/CFLIST
@@ -1,3 +1,4 @@
 LOCK01
 LOCK02
 LOCK03
+LOCK04
\ No newline at end of file
diff --git a/tools/testing/selftests/rcutorture/configs/lock/LOCK04 b/tools/testing/selftests/rcutorture/configs/lock/LOCK04
new file mode 100644
index 000000000000..1d1da1477fc3
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/configs/lock/LOCK04
@@ -0,0 +1,6 @@
+CONFIG_SMP=y
+CONFIG_NR_CPUS=4
+CONFIG_HOTPLUG_CPU=y
+CONFIG_PREEMPT_NONE=n
+CONFIG_PREEMPT_VOLUNTARY=n
+CONFIG_PREEMPT=y
diff --git a/tools/testing/selftests/rcutorture/configs/lock/LOCK04.boot b/too