[PATCH 1/2] locktorture: Support rtmutex torturing

[PATCH 1/2] locktorture: Support rtmutex torturing

[Davidlohr Bueso]

Real time mutexes is one of the few general primitives
that we do not have in locktorture. Address this -- a few
considerations:

o To spice things up, enable competing thread(s) to become
rt, such that we can stress different prio boosting paths
in the rtmutex code. Introduce a ->task_boost callback,
only used by rtmutex-torturer. Tasks will boost/deboost
around every 50k (arbitrarily) lock/unlock operations.

o Hold times are similar to what we have for other locks:
only occasionally having longer hold times (per ~200k ops).
So we roughly do two full rt boost+deboosting ops with
short hold times.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
---
 Documentation/locking/locktorture.txt              |   3 +
 kernel/locking/locktorture.c                       | 114 ++++++++++++++++++++-
 .../selftests/rcutorture/configs/lock/CFLIST       |   3 +-
 .../selftests/rcutorture/configs/lock/LOCK05       |   6 ++
 .../selftests/rcutorture/configs/lock/LOCK05.boot  |   1 +
 5 files changed, 124 insertions(+), 3 deletions(-)
 create mode 100644 tools/testing/selftests/rcutorture/configs/lock/LOCK05
 create mode 100644 tools/testing/selftests/rcutorture/configs/lock/LOCK05.boot

diff --git a/Documentation/locking/locktorture.txt b/Documentation/locking/locktorture.txt
index 619f2bb..a2ef3a9 100644
--- a/Documentation/locking/locktorture.txt
+++ b/Documentation/locking/locktorture.txt
@@ -52,6 +52,9 @@ torture_type	  Type of lock to torture. By default, only spinlocks will
 
 		     o "mutex_lock": mutex_lock() and mutex_unlock() pairs.
 
+		     o "rtmutex_lock": rtmutex_lock() and rtmutex_unlock()
+				       pairs. Kernel must have CONFIG_RT_MUTEX=y.
+
 		     o "rwsem_lock": read/write down() and up() semaphore pairs.
 
 torture_runnable  Start locktorture at boot time in the case where the
diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
index 3224418..e1ca7a2 100644
--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -17,12 +17,14 @@
  *
  * Copyright (C) IBM Corporation, 2014
  *
- * Author: Paul E. McKenney <paulmck@us.ibm.com>
+ * Authors: Paul E. McKenney <paulmck@us.ibm.com>
+ *          Davidlohr Bueso <dave@stgolabs.net>
  *	Based on kernel/rcu/torture.c.
  */
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/kthread.h>
+#include <linux/sched/rt.h>
 #include <linux/spinlock.h>
 #include <linux/rwlock.h>
 #include <linux/mutex.h>
@@ -91,11 +93,13 @@ struct lock_torture_ops {
 	void (*init)(void);
 	int (*writelock)(void);
 	void (*write_delay)(struct torture_random_state *trsp);
+	void (*task_boost)(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;
+
+	unsigned long flags; /* for irq spinlocks */
 	const char *name;
 };
 
@@ -139,9 +143,15 @@ static void torture_lock_busted_write_unlock(void)
 	  /* BUGGY, do not use in real life!!! */
 }
 
+static void torture_boost_dummy(struct torture_random_state *trsp)
+{
+	/* Only rtmutexes care about priority */
+}
+
 static struct lock_torture_ops lock_busted_ops = {
 	.writelock	= torture_lock_busted_write_lock,
 	.write_delay	= torture_lock_busted_write_delay,
+	.task_boost     = torture_boost_dummy,
 	.writeunlock	= torture_lock_busted_write_unlock,
 	.readlock       = NULL,
 	.read_delay     = NULL,
@@ -185,6 +195,7 @@ static void torture_spin_lock_write_unlock(void) __releases(torture_spinlock)
 static struct lock_torture_ops spin_lock_ops = {
 	.writelock	= torture_spin_lock_write_lock,
 	.write_delay	= torture_spin_lock_write_delay,
+	.task_boost     = torture_boost_dummy,
 	.writeunlock	= torture_spin_lock_write_unlock,
 	.readlock       = NULL,
 	.read_delay     = NULL,
@@ -211,6 +222,7 @@ __releases(torture_spinlock)
 static struct lock_torture_ops spin_lock_irq_ops = {
 	.writelock	= torture_spin_lock_write_lock_irq,
 	.write_delay	= torture_spin_lock_write_delay,
+	.task_boost     = torture_boost_dummy,
 	.writeunlock	= torture_lock_spin_write_unlock_irq,
 	.readlock       = NULL,
 	.read_delay     = NULL,
@@ -275,6 +287,7 @@ static void torture_rwlock_read_unlock(void) __releases(torture_rwlock)
 static struct lock_torture_ops rw_lock_ops = {
 	.writelock	= torture_rwlock_write_lock,
 	.write_delay	= torture_rwlock_write_delay,
+	.task_boost     = torture_boost_dummy,
 	.writeunlock	= torture_rwlock_write_unlock,
 	.readlock       = torture_rwlock_read_lock,
 	.read_delay     = torture_rwlock_read_delay,
@@ -315,6 +328,7 @@ __releases(torture_rwlock)
 static struct lock_torture_ops rw_lock_irq_ops = {
 	.writelock	= torture_rwlock_write_lock_irq,
 	.write_delay	= torture_rwlock_write_delay,
+	.task_boost     = torture_boost_dummy,
 	.writeunlock	= torture_rwlock_write_unlock_irq,
 	.readlock       = torture_rwlock_read_lock_irq,
 	.read_delay     = torture_rwlock_read_delay,
@@ -354,6 +368,7 @@ static void torture_mutex_unlock(void) __releases(torture_mutex)
 static struct lock_torture_ops mutex_lock_ops = {
 	.writelock	= torture_mutex_lock,
 	.write_delay	= torture_mutex_delay,
+	.task_boost     = torture_boost_dummy,
 	.writeunlock	= torture_mutex_unlock,
 	.readlock       = NULL,
 	.read_delay     = NULL,
@@ -361,6 +376,90 @@ static struct lock_torture_ops mutex_lock_ops = {
 	.name		= "mutex_lock"
 };
 
+#ifdef CONFIG_RT_MUTEXES
+static DEFINE_RT_MUTEX(torture_rtmutex);
+
+static int torture_rtmutex_lock(void) __acquires(torture_rtmutex)
+{
+	rt_mutex_lock(&torture_rtmutex);
+	return 0;
+}
+
+static void torture_rtmutex_boost(struct torture_random_state *trsp)
+{
+	int policy;
+	struct sched_param param;
+	const unsigned int factor = 50000; /* yes, quite arbitrary */
+
+	if (!rt_task(current)) {
+		/*
+		 * (1) Boost priority once every ~50k operations. When the
+		 * task tries to take the lock, the rtmutex it will account
+		 * for the new priority, and do any corresponding pi-dance.
+		 */
+		if (!(torture_random(trsp) %
+		      (cxt.nrealwriters_stress * factor))) {
+			policy = SCHED_FIFO;
+			param.sched_priority = MAX_RT_PRIO - 1;
+		} else /* common case, do nothing */
+			return;
+	} else {
+		/*
+		 * The task will remain boosted for another ~500k operations,
+		 * then restored back to its original prio, and so forth.
+		 *
+		 * When @trsp is nil, we want to force-reset the task for
+		 * stopping the kthread.
+		 */
+		if (!trsp || !(torture_random(trsp) %
+			       (cxt.nrealwriters_stress * factor * 2))) {
+			policy = SCHED_NORMAL;
+			param.sched_priority = 0;
+		} else /* common case, do nothing */
+			return;
+	}
+
+	sched_setscheduler_nocheck(current, policy, &param);
+}
+
+static void torture_rtmutex_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);
+	if (!(torture_random(trsp) %
+	      (cxt.nrealwriters_stress * 2 * shortdelay_us)))
+		udelay(shortdelay_us);
+#ifdef CONFIG_PREEMPT
+	if (!(torture_random(trsp) % (cxt.nrealwriters_stress * 20000)))
+		preempt_schedule();  /* Allow test to be preempted. */
+#endif
+}
+
+static void torture_rtmutex_unlock(void) __releases(torture_rtmutex)
+{
+	rt_mutex_unlock(&torture_rtmutex);
+}
+
+static struct lock_torture_ops rtmutex_lock_ops = {
+	.writelock	= torture_rtmutex_lock,
+	.write_delay	= torture_rtmutex_delay,
+	.task_boost     = torture_rtmutex_boost,
+	.writeunlock	= torture_rtmutex_unlock,
+	.readlock       = NULL,
+	.read_delay     = NULL,
+	.readunlock     = NULL,
+	.name		= "rtmutex_lock"
+};
+#endif
+
 static DECLARE_RWSEM(torture_rwsem);
 static int torture_rwsem_down_write(void) __acquires(torture_rwsem)
 {
@@ -419,6 +518,7 @@ static void torture_rwsem_up_read(void) __releases(torture_rwsem)
 static struct lock_torture_ops rwsem_lock_ops = {
 	.writelock	= torture_rwsem_down_write,
 	.write_delay	= torture_rwsem_write_delay,
+	.task_boost     = torture_boost_dummy,
 	.writeunlock	= torture_rwsem_up_write,
 	.readlock       = torture_rwsem_down_read,
 	.read_delay     = torture_rwsem_read_delay,
@@ -442,6 +542,7 @@ static int lock_torture_writer(void *arg)
 		if ((torture_random(&rand) & 0xfffff) == 0)
 			schedule_timeout_uninterruptible(1);
 
+		cxt.cur_ops->task_boost(&rand);
 		cxt.cur_ops->writelock();
 		if (WARN_ON_ONCE(lock_is_write_held))
 			lwsp->n_lock_fail++;
@@ -456,6 +557,8 @@ static int lock_torture_writer(void *arg)
 
 		stutter_wait("lock_torture_writer");
 	} while (!torture_must_stop());
+
+	cxt.cur_ops->task_boost(NULL); /* reset prio */
 	torture_kthread_stopping("lock_torture_writer");
 	return 0;
 }
@@ -642,6 +745,9 @@ static int __init lock_torture_init(void)
 		&spin_lock_ops, &spin_lock_irq_ops,
 		&rw_lock_ops, &rw_lock_irq_ops,
 		&mutex_lock_ops,
+#ifdef CONFIG_RT_MUTEXES
+		&rtmutex_lock_ops,
+#endif
 		&rwsem_lock_ops,
 	};
 
@@ -676,6 +782,10 @@ static int __init lock_torture_init(void)
 	if (strncmp(torture_type, "mutex", 5) == 0)
 		cxt.debug_lock = true;
 #endif
+#ifdef CONFIG_DEBUG_RT_MUTEXES
+	if (strncmp(torture_type, "rtmutex", 7) == 0)
+		cxt.debug_lock = true;
+#endif
 #ifdef CONFIG_DEBUG_SPINLOCK
 	if ((strncmp(torture_type, "spin", 4) == 0) ||
 	    (strncmp(torture_type, "rw_lock", 7) == 0))
diff --git a/tools/testing/selftests/rcutorture/configs/lock/CFLIST b/tools/testing/selftests/rcutorture/configs/lock/CFLIST
index 6910b73..6ed3279 100644
--- a/tools/testing/selftests/rcutorture/configs/lock/CFLIST
+++ b/tools/testing/selftests/rcutorture/configs/lock/CFLIST
@@ -1,4 +1,5 @@
 LOCK01
 LOCK02
 LOCK03
-LOCK04
\ No newline at end of file
+LOCK04
+LOCK05
diff --git a/tools/testing/selftests/rcutorture/configs/lock/LOCK05 b/tools/testing/selftests/rcutorture/configs/lock/LOCK05
new file mode 100644
index 0000000..1d1da14
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/configs/lock/LOCK05
@@ -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/LOCK05.boot b/tools/testing/selftests/rcutorture/configs/lock/LOCK05.boot
new file mode 100644
index 0000000..8ac3730
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/configs/lock/LOCK05.boot
@@ -0,0 +1 @@
+locktorture.torture_type=rtmutex_lock
-- 
2.1.4

[PATCH 2/2] locktorture: 'tis a slow death

[Davidlohr Bueso]

... sorry couldn't help myself.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
---
 kernel/locking/locktorture.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
index e1ca7a2..3861d37 100644
--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -17,6 +17,17 @@
  *
  * Copyright (C) IBM Corporation, 2014
  *
+ *                 ___
+ *      .----.      __) `\
+ *      | == |     < __=- |
+ *   ___| :: |___   \\ `)/
+ *   \  `----'  /\  (\) (
+ *    \   `.   /( \/ /\\
+ *    |    :   | \  /  \\
+ *    \   _._  /  `"   <_>
+ *     xxx(o)xx
+ *              7jan0 cjr
+ *
  * Authors: Paul E. McKenney <paulmck@us.ibm.com>
  *          Davidlohr Bueso <dave@stgolabs.net>
  *	Based on kernel/rcu/torture.c.
-- 
2.1.4

Re: [PATCH 2/2] locktorture: 'tis a slow death

[Paul E. McKenney]

On Wed, Jul 22, 2015 at 02:07:28PM -0700, Davidlohr Bueso wrote:
> ... sorry couldn't help myself.
> 
> Signed-off-by: Davidlohr Bueso <dbueso@suse.de>

Cute!!!

That said, I strongly suggest reviewing these two web pages:

	http://www.ascii-art.de/info/copyright/
	http://www.ascii-art.de/ascii/ab/axe.txt

And then also the DCO in Documentation/SubmittingPatches, which I
reproduce here:

        Developer's Certificate of Origin 1.1

        By making a contribution to this project, I certify that:

        (a) The contribution was created in whole or in part by me and I
            have the right to submit it under the open source license
            indicated in the file; or

        (b) The contribution is based upon previous work that, to the best
            of my knowledge, is covered under an appropriate open source
            license and I have the right under that license to submit that
            work with modifications, whether created in whole or in part
            by me, under the same open source license (unless I am
            permitted to submit under a different license), as indicated
            in the file; or

        (c) The contribution was provided directly to me by some other
            person who certified (a), (b) or (c) and I have not modified
            it.

        (d) I understand and agree that this project and the contribution
            are public and that a record of the contribution (including all
            personal information I submit with it, including my sign-off) is
            maintained indefinitely and may be redistributed consistent with
            this project or the open source license(s) involved.

	then you just add a line saying

		Signed-off-by: Random J Developer <random@developer.example.org>

	using your real name (sorry, no pseudonyms or anonymous contributions.)

I need to see something more than what I am seeing for me to be able
to accept this, cute though it unarguably is.

							Thanx, Paul

> ---
>  kernel/locking/locktorture.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
> index e1ca7a2..3861d37 100644
> --- a/kernel/locking/locktorture.c
> +++ b/kernel/locking/locktorture.c
> @@ -17,6 +17,17 @@
>   *
>   * Copyright (C) IBM Corporation, 2014
>   *
> + *                 ___
> + *      .----.      __) `\
> + *      | == |     < __=- |
> + *   ___| :: |___   \\ `)/
> + *   \  `----'  /\  (\) (
> + *    \   `.   /( \/ /\\
> + *    |    :   | \  /  \\
> + *    \   _._  /  `"   <_>
> + *     xxx(o)xx
> + *              7jan0 cjr
> + *
>   * Authors: Paul E. McKenney <paulmck@us.ibm.com>
>   *          Davidlohr Bueso <dave@stgolabs.net>
>   *	Based on kernel/rcu/torture.c.
> -- 
> 2.1.4
> 

Re: [PATCH 1/2] locktorture: Support rtmutex torturing

[Paul E. McKenney]

On Wed, Jul 22, 2015 at 02:07:27PM -0700, Davidlohr Bueso wrote:
> Real time mutexes is one of the few general primitives
> that we do not have in locktorture. Address this -- a few
> considerations:
> 
> o To spice things up, enable competing thread(s) to become
> rt, such that we can stress different prio boosting paths
> in the rtmutex code. Introduce a ->task_boost callback,
> only used by rtmutex-torturer. Tasks will boost/deboost
> around every 50k (arbitrarily) lock/unlock operations.
> 
> o Hold times are similar to what we have for other locks:
> only occasionally having longer hold times (per ~200k ops).
> So we roughly do two full rt boost+deboosting ops with
> short hold times.
> 
> Signed-off-by: Davidlohr Bueso <dbueso@suse.de>

I have queued this one for testing, and by default would push it into
the 4.4 merge window (the one after next).  Please let me know if you
want it sooner.

At some point, I would guess that you would want some boot parameters
to control some aspects of the test, but given that you are the major
use of this, I defer to your judgment on if and when.  ;-)

							Thanx, Paul

> ---
>  Documentation/locking/locktorture.txt              |   3 +
>  kernel/locking/locktorture.c                       | 114 ++++++++++++++++++++-
>  .../selftests/rcutorture/configs/lock/CFLIST       |   3 +-
>  .../selftests/rcutorture/configs/lock/LOCK05       |   6 ++
>  .../selftests/rcutorture/configs/lock/LOCK05.boot  |   1 +
>  5 files changed, 124 insertions(+), 3 deletions(-)
>  create mode 100644 tools/testing/selftests/rcutorture/configs/lock/LOCK05
>  create mode 100644 tools/testing/selftests/rcutorture/configs/lock/LOCK05.boot
> 
> diff --git a/Documentation/locking/locktorture.txt b/Documentation/locking/locktorture.txt
> index 619f2bb..a2ef3a9 100644
> --- a/Documentation/locking/locktorture.txt
> +++ b/Documentation/locking/locktorture.txt
> @@ -52,6 +52,9 @@ torture_type	  Type of lock to torture. By default, only spinlocks will
> 
>  		     o "mutex_lock": mutex_lock() and mutex_unlock() pairs.
> 
> +		     o "rtmutex_lock": rtmutex_lock() and rtmutex_unlock()
> +				       pairs. Kernel must have CONFIG_RT_MUTEX=y.
> +
>  		     o "rwsem_lock": read/write down() and up() semaphore pairs.
> 
>  torture_runnable  Start locktorture at boot time in the case where the
> diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
> index 3224418..e1ca7a2 100644
> --- a/kernel/locking/locktorture.c
> +++ b/kernel/locking/locktorture.c
> @@ -17,12 +17,14 @@
>   *
>   * Copyright (C) IBM Corporation, 2014
>   *
> - * Author: Paul E. McKenney <paulmck@us.ibm.com>
> + * Authors: Paul E. McKenney <paulmck@us.ibm.com>
> + *          Davidlohr Bueso <dave@stgolabs.net>
>   *	Based on kernel/rcu/torture.c.
>   */
>  #include <linux/kernel.h>
>  #include <linux/module.h>
>  #include <linux/kthread.h>
> +#include <linux/sched/rt.h>
>  #include <linux/spinlock.h>
>  #include <linux/rwlock.h>
>  #include <linux/mutex.h>
> @@ -91,11 +93,13 @@ struct lock_torture_ops {
>  	void (*init)(void);
>  	int (*writelock)(void);
>  	void (*write_delay)(struct torture_random_state *trsp);
> +	void (*task_boost)(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;
> +
> +	unsigned long flags; /* for irq spinlocks */
>  	const char *name;
>  };
> 
> @@ -139,9 +143,15 @@ static void torture_lock_busted_write_unlock(void)
>  	  /* BUGGY, do not use in real life!!! */
>  }
> 
> +static void torture_boost_dummy(struct torture_random_state *trsp)
> +{
> +	/* Only rtmutexes care about priority */
> +}
> +
>  static struct lock_torture_ops lock_busted_ops = {
>  	.writelock	= torture_lock_busted_write_lock,
>  	.write_delay	= torture_lock_busted_write_delay,
> +	.task_boost     = torture_boost_dummy,
>  	.writeunlock	= torture_lock_busted_write_unlock,
>  	.readlock       = NULL,
>  	.read_delay     = NULL,
> @@ -185,6 +195,7 @@ static void torture_spin_lock_write_unlock(void) __releases(torture_spinlock)
>  static struct lock_torture_ops spin_lock_ops = {
>  	.writelock	= torture_spin_lock_write_lock,
>  	.write_delay	= torture_spin_lock_write_delay,
> +	.task_boost     = torture_boost_dummy,
>  	.writeunlock	= torture_spin_lock_write_unlock,
>  	.readlock       = NULL,
>  	.read_delay     = NULL,
> @@ -211,6 +222,7 @@ __releases(torture_spinlock)
>  static struct lock_torture_ops spin_lock_irq_ops = {
>  	.writelock	= torture_spin_lock_write_lock_irq,
>  	.write_delay	= torture_spin_lock_write_delay,
> +	.task_boost     = torture_boost_dummy,
>  	.writeunlock	= torture_lock_spin_write_unlock_irq,
>  	.readlock       = NULL,
>  	.read_delay     = NULL,
> @@ -275,6 +287,7 @@ static void torture_rwlock_read_unlock(void) __releases(torture_rwlock)
>  static struct lock_torture_ops rw_lock_ops = {
>  	.writelock	= torture_rwlock_write_lock,
>  	.write_delay	= torture_rwlock_write_delay,
> +	.task_boost     = torture_boost_dummy,
>  	.writeunlock	= torture_rwlock_write_unlock,
>  	.readlock       = torture_rwlock_read_lock,
>  	.read_delay     = torture_rwlock_read_delay,
> @@ -315,6 +328,7 @@ __releases(torture_rwlock)
>  static struct lock_torture_ops rw_lock_irq_ops = {
>  	.writelock	= torture_rwlock_write_lock_irq,
>  	.write_delay	= torture_rwlock_write_delay,
> +	.task_boost     = torture_boost_dummy,
>  	.writeunlock	= torture_rwlock_write_unlock_irq,
>  	.readlock       = torture_rwlock_read_lock_irq,
>  	.read_delay     = torture_rwlock_read_delay,
> @@ -354,6 +368,7 @@ static void torture_mutex_unlock(void) __releases(torture_mutex)
>  static struct lock_torture_ops mutex_lock_ops = {
>  	.writelock	= torture_mutex_lock,
>  	.write_delay	= torture_mutex_delay,
> +	.task_boost     = torture_boost_dummy,
>  	.writeunlock	= torture_mutex_unlock,
>  	.readlock       = NULL,
>  	.read_delay     = NULL,
> @@ -361,6 +376,90 @@ static struct lock_torture_ops mutex_lock_ops = {
>  	.name		= "mutex_lock"
>  };
> 
> +#ifdef CONFIG_RT_MUTEXES
> +static DEFINE_RT_MUTEX(torture_rtmutex);
> +
> +static int torture_rtmutex_lock(void) __acquires(torture_rtmutex)
> +{
> +	rt_mutex_lock(&torture_rtmutex);
> +	return 0;
> +}
> +
> +static void torture_rtmutex_boost(struct torture_random_state *trsp)
> +{
> +	int policy;
> +	struct sched_param param;
> +	const unsigned int factor = 50000; /* yes, quite arbitrary */
> +
> +	if (!rt_task(current)) {
> +		/*
> +		 * (1) Boost priority once every ~50k operations. When the
> +		 * task tries to take the lock, the rtmutex it will account
> +		 * for the new priority, and do any corresponding pi-dance.
> +		 */
> +		if (!(torture_random(trsp) %
> +		      (cxt.nrealwriters_stress * factor))) {
> +			policy = SCHED_FIFO;
> +			param.sched_priority = MAX_RT_PRIO - 1;
> +		} else /* common case, do nothing */
> +			return;
> +	} else {
> +		/*
> +		 * The task will remain boosted for another ~500k operations,
> +		 * then restored back to its original prio, and so forth.
> +		 *
> +		 * When @trsp is nil, we want to force-reset the task for
> +		 * stopping the kthread.
> +		 */
> +		if (!trsp || !(torture_random(trsp) %
> +			       (cxt.nrealwriters_stress * factor * 2))) {
> +			policy = SCHED_NORMAL;
> +			param.sched_priority = 0;
> +		} else /* common case, do nothing */
> +			return;
> +	}
> +
> +	sched_setscheduler_nocheck(current, policy, &param);
> +}
> +
> +static void torture_rtmutex_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);
> +	if (!(torture_random(trsp) %
> +	      (cxt.nrealwriters_stress * 2 * shortdelay_us)))
> +		udelay(shortdelay_us);
> +#ifdef CONFIG_PREEMPT
> +	if (!(torture_random(trsp) % (cxt.nrealwriters_stress * 20000)))
> +		preempt_schedule();  /* Allow test to be preempted. */
> +#endif
> +}
> +
> +static void torture_rtmutex_unlock(void) __releases(torture_rtmutex)
> +{
> +	rt_mutex_unlock(&torture_rtmutex);
> +}
> +
> +static struct lock_torture_ops rtmutex_lock_ops = {
> +	.writelock	= torture_rtmutex_lock,
> +	.write_delay	= torture_rtmutex_delay,
> +	.task_boost     = torture_rtmutex_boost,
> +	.writeunlock	= torture_rtmutex_unlock,
> +	.readlock       = NULL,
> +	.read_delay     = NULL,
> +	.readunlock     = NULL,
> +	.name		= "rtmutex_lock"
> +};
> +#endif
> +
>  static DECLARE_RWSEM(torture_rwsem);
>  static int torture_rwsem_down_write(void) __acquires(torture_rwsem)
>  {
> @@ -419,6 +518,7 @@ static void torture_rwsem_up_read(void) __releases(torture_rwsem)
>  static struct lock_torture_ops rwsem_lock_ops = {
>  	.writelock	= torture_rwsem_down_write,
>  	.write_delay	= torture_rwsem_write_delay,
> +	.task_boost     = torture_boost_dummy,
>  	.writeunlock	= torture_rwsem_up_write,
>  	.readlock       = torture_rwsem_down_read,
>  	.read_delay     = torture_rwsem_read_delay,
> @@ -442,6 +542,7 @@ static int lock_torture_writer(void *arg)
>  		if ((torture_random(&rand) & 0xfffff) == 0)
>  			schedule_timeout_uninterruptible(1);
> 
> +		cxt.cur_ops->task_boost(&rand);
>  		cxt.cur_ops->writelock();
>  		if (WARN_ON_ONCE(lock_is_write_held))
>  			lwsp->n_lock_fail++;
> @@ -456,6 +557,8 @@ static int lock_torture_writer(void *arg)
> 
>  		stutter_wait("lock_torture_writer");
>  	} while (!torture_must_stop());
> +
> +	cxt.cur_ops->task_boost(NULL); /* reset prio */
>  	torture_kthread_stopping("lock_torture_writer");
>  	return 0;
>  }
> @@ -642,6 +745,9 @@ static int __init lock_torture_init(void)
>  		&spin_lock_ops, &spin_lock_irq_ops,
>  		&rw_lock_ops, &rw_lock_irq_ops,
>  		&mutex_lock_ops,
> +#ifdef CONFIG_RT_MUTEXES
> +		&rtmutex_lock_ops,
> +#endif
>  		&rwsem_lock_ops,
>  	};
> 
> @@ -676,6 +782,10 @@ static int __init lock_torture_init(void)
>  	if (strncmp(torture_type, "mutex", 5) == 0)
>  		cxt.debug_lock = true;
>  #endif
> +#ifdef CONFIG_DEBUG_RT_MUTEXES
> +	if (strncmp(torture_type, "rtmutex", 7) == 0)
> +		cxt.debug_lock = true;
> +#endif
>  #ifdef CONFIG_DEBUG_SPINLOCK
>  	if ((strncmp(torture_type, "spin", 4) == 0) ||
>  	    (strncmp(torture_type, "rw_lock", 7) == 0))
> diff --git a/tools/testing/selftests/rcutorture/configs/lock/CFLIST b/tools/testing/selftests/rcutorture/configs/lock/CFLIST
> index 6910b73..6ed3279 100644
> --- a/tools/testing/selftests/rcutorture/configs/lock/CFLIST
> +++ b/tools/testing/selftests/rcutorture/configs/lock/CFLIST
> @@ -1,4 +1,5 @@
>  LOCK01
>  LOCK02
>  LOCK03
> -LOCK04
> \ No newline at end of file
> +LOCK04
> +LOCK05
> diff --git a/tools/testing/selftests/rcutorture/configs/lock/LOCK05 b/tools/testing/selftests/rcutorture/configs/lock/LOCK05
> new file mode 100644
> index 0000000..1d1da14
> --- /dev/null
> +++ b/tools/testing/selftests/rcutorture/configs/lock/LOCK05
> @@ -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/LOCK05.boot b/tools/testing/selftests/rcutorture/configs/lock/LOCK05.boot
> new file mode 100644
> index 0000000..8ac3730
> --- /dev/null
> +++ b/tools/testing/selftests/rcutorture/configs/lock/LOCK05.boot
> @@ -0,0 +1 @@
> +locktorture.torture_type=rtmutex_lock
> -- 
> 2.1.4
> 

Re: [PATCH 2/2] locktorture: 'tis a slow death

[Davidlohr Bueso]

On Wed, 2015-07-22 at 17:13 -0700, Paul E. McKenney wrote:
> I need to see something more than what I am seeing for me to be able
> to accept this, cute though it unarguably is.

heh I didn't consider copyright for this kind of stuff. And was naive to
think that keeping his (what I assume to be) initials was enough. I've
contacted the author for permission to use his work.

But yeah, I had to laugh when I saw this. Although I probably triggered
some red flag by googling 'torture' and 'weapons' :-)

Thanks,
Davidlohr

Re: [PATCH 1/2] locktorture: Support rtmutex torturing

[Davidlohr Bueso]

On Wed, 2015-07-22 at 17:17 -0700, Paul E. McKenney wrote:
> On Wed, Jul 22, 2015 at 02:07:27PM -0700, Davidlohr Bueso wrote:
> > Real time mutexes is one of the few general primitives
> > that we do not have in locktorture. Address this -- a few
> > considerations:
> > 
> > o To spice things up, enable competing thread(s) to become
> > rt, such that we can stress different prio boosting paths
> > in the rtmutex code. Introduce a ->task_boost callback,
> > only used by rtmutex-torturer. Tasks will boost/deboost
> > around every 50k (arbitrarily) lock/unlock operations.
> > 
> > o Hold times are similar to what we have for other locks:
> > only occasionally having longer hold times (per ~200k ops).
> > So we roughly do two full rt boost+deboosting ops with
> > short hold times.
> > 
> > Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
> 
> I have queued this one for testing, and by default would push it into
> the 4.4 merge window (the one after next).  Please let me know if you
> want it sooner.

Thanks, although here's a v2 with some small fixes:

- comment when reseting prio s/500k/50k.
- when reseting prio, there's a chance a non-rt task can be converted
(which we certainly don't want). Check trsp for nil.

While I was planning for 4.3, I can certainly wait a few more weeks for
4.4. Either way is fine.

Thanks,
Davidlohr

8<-------------------------------------------------------------------
[PATCH v2] locktorture: Support rtmutex torturing

Real time mutexes is one of the few general primitives
that we do not have in locktorture. Address this -- a few
considerations:

o To spice things up, enable competing thread(s) to become
rt, such that we can stress different prio boosting paths
in the rtmutex code. Introduce a ->task_boost callback,
only used by rtmutex-torturer. Tasks will boost/deboost
around every 50k (arbitrarily) lock/unlock operations.

o Hold times are similar to what we have for other locks:
only occasionally having longer hold times (per ~200k ops).
So we roughly do two full rt boost+deboosting ops with
short hold times.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
---
 Documentation/locking/locktorture.txt              |   3 +
 kernel/locking/locktorture.c                       | 114 ++++++++++++++++++++-
 .../selftests/rcutorture/configs/lock/CFLIST       |   3 +-
 .../selftests/rcutorture/configs/lock/LOCK05       |   6 ++
 .../selftests/rcutorture/configs/lock/LOCK05.boot  |   1 +
 5 files changed, 124 insertions(+), 3 deletions(-)
 create mode 100644 tools/testing/selftests/rcutorture/configs/lock/LOCK05
 create mode 100644 tools/testing/selftests/rcutorture/configs/lock/LOCK05.boot

diff --git a/Documentation/locking/locktorture.txt b/Documentation/locking/locktorture.txt
index 619f2bb..a2ef3a9 100644
--- a/Documentation/locking/locktorture.txt
+++ b/Documentation/locking/locktorture.txt
@@ -52,6 +52,9 @@ torture_type	  Type of lock to torture. By default, only spinlocks will
 
 		     o "mutex_lock": mutex_lock() and mutex_unlock() pairs.
 
+		     o "rtmutex_lock": rtmutex_lock() and rtmutex_unlock()
+				       pairs. Kernel must have CONFIG_RT_MUTEX=y.
+
 		     o "rwsem_lock": read/write down() and up() semaphore pairs.
 
 torture_runnable  Start locktorture at boot time in the case where the
diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
index 3224418..26ddd63 100644
--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -17,12 +17,14 @@
  *
  * Copyright (C) IBM Corporation, 2014
  *
- * Author: Paul E. McKenney <paulmck@us.ibm.com>
+ * Authors: Paul E. McKenney <paulmck@us.ibm.com>
+ *          Davidlohr Bueso <dave@stgolabs.net>
  *	Based on kernel/rcu/torture.c.
  */
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/kthread.h>
+#include <linux/sched/rt.h>
 #include <linux/spinlock.h>
 #include <linux/rwlock.h>
 #include <linux/mutex.h>
@@ -91,11 +93,13 @@ struct lock_torture_ops {
 	void (*init)(void);
 	int (*writelock)(void);
 	void (*write_delay)(struct torture_random_state *trsp);
+	void (*task_boost)(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;
+
+	unsigned long flags; /* for irq spinlocks */
 	const char *name;
 };
 
@@ -139,9 +143,15 @@ static void torture_lock_busted_write_unlock(void)
 	  /* BUGGY, do not use in real life!!! */
 }
 
+static void torture_boost_dummy(struct torture_random_state *trsp)
+{
+	/* Only rtmutexes care about priority */
+}
+
 static struct lock_torture_ops lock_busted_ops = {
 	.writelock	= torture_lock_busted_write_lock,
 	.write_delay	= torture_lock_busted_write_delay,
+	.task_boost     = torture_boost_dummy,
 	.writeunlock	= torture_lock_busted_write_unlock,
 	.readlock       = NULL,
 	.read_delay     = NULL,
@@ -185,6 +195,7 @@ static void torture_spin_lock_write_unlock(void) __releases(torture_spinlock)
 static struct lock_torture_ops spin_lock_ops = {
 	.writelock	= torture_spin_lock_write_lock,
 	.write_delay	= torture_spin_lock_write_delay,
+	.task_boost     = torture_boost_dummy,
 	.writeunlock	= torture_spin_lock_write_unlock,
 	.readlock       = NULL,
 	.read_delay     = NULL,
@@ -211,6 +222,7 @@ __releases(torture_spinlock)
 static struct lock_torture_ops spin_lock_irq_ops = {
 	.writelock	= torture_spin_lock_write_lock_irq,
 	.write_delay	= torture_spin_lock_write_delay,
+	.task_boost     = torture_boost_dummy,
 	.writeunlock	= torture_lock_spin_write_unlock_irq,
 	.readlock       = NULL,
 	.read_delay     = NULL,
@@ -275,6 +287,7 @@ static void torture_rwlock_read_unlock(void) __releases(torture_rwlock)
 static struct lock_torture_ops rw_lock_ops = {
 	.writelock	= torture_rwlock_write_lock,
 	.write_delay	= torture_rwlock_write_delay,
+	.task_boost     = torture_boost_dummy,
 	.writeunlock	= torture_rwlock_write_unlock,
 	.readlock       = torture_rwlock_read_lock,
 	.read_delay     = torture_rwlock_read_delay,
@@ -315,6 +328,7 @@ __releases(torture_rwlock)
 static struct lock_torture_ops rw_lock_irq_ops = {
 	.writelock	= torture_rwlock_write_lock_irq,
 	.write_delay	= torture_rwlock_write_delay,
+	.task_boost     = torture_boost_dummy,
 	.writeunlock	= torture_rwlock_write_unlock_irq,
 	.readlock       = torture_rwlock_read_lock_irq,
 	.read_delay     = torture_rwlock_read_delay,
@@ -354,6 +368,7 @@ static void torture_mutex_unlock(void) __releases(torture_mutex)
 static struct lock_torture_ops mutex_lock_ops = {
 	.writelock	= torture_mutex_lock,
 	.write_delay	= torture_mutex_delay,
+	.task_boost     = torture_boost_dummy,
 	.writeunlock	= torture_mutex_unlock,
 	.readlock       = NULL,
 	.read_delay     = NULL,
@@ -361,6 +376,90 @@ static struct lock_torture_ops mutex_lock_ops = {
 	.name		= "mutex_lock"
 };
 
+#ifdef CONFIG_RT_MUTEXES
+static DEFINE_RT_MUTEX(torture_rtmutex);
+
+static int torture_rtmutex_lock(void) __acquires(torture_rtmutex)
+{
+	rt_mutex_lock(&torture_rtmutex);
+	return 0;
+}
+
+static void torture_rtmutex_boost(struct torture_random_state *trsp)
+{
+	int policy;
+	struct sched_param param;
+	const unsigned int factor = 50000; /* yes, quite arbitrary */
+
+	if (!rt_task(current)) {
+		/*
+		 * (1) Boost priority once every ~50k operations. When the
+		 * task tries to take the lock, the rtmutex it will account
+		 * for the new priority, and do any corresponding pi-dance.
+		 */
+		if (trsp && !(torture_random(trsp) %
+			      (cxt.nrealwriters_stress * factor))) {
+			policy = SCHED_FIFO;
+			param.sched_priority = MAX_RT_PRIO - 1;
+		} else /* common case, do nothing */
+			return;
+	} else {
+		/*
+		 * (2) The task will remain boosted for another ~50k operations,
+		 * then restored back to its original prio, and so forth.
+		 *
+		 * When @trsp is nil, we want to force-reset the task for
+		 * stopping the kthread.
+		 */
+		if (!trsp || !(torture_random(trsp) %
+			       (cxt.nrealwriters_stress * factor * 2))) {
+			policy = SCHED_NORMAL;
+			param.sched_priority = 0;
+		} else /* common case, do nothing */
+			return;
+	}
+
+	sched_setscheduler_nocheck(current, policy, &param);
+}
+
+static void torture_rtmutex_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);
+	if (!(torture_random(trsp) %
+	      (cxt.nrealwriters_stress * 2 * shortdelay_us)))
+		udelay(shortdelay_us);
+#ifdef CONFIG_PREEMPT
+	if (!(torture_random(trsp) % (cxt.nrealwriters_stress * 20000)))
+		preempt_schedule();  /* Allow test to be preempted. */
+#endif
+}
+
+static void torture_rtmutex_unlock(void) __releases(torture_rtmutex)
+{
+	rt_mutex_unlock(&torture_rtmutex);
+}
+
+static struct lock_torture_ops rtmutex_lock_ops = {
+	.writelock	= torture_rtmutex_lock,
+	.write_delay	= torture_rtmutex_delay,
+	.task_boost     = torture_rtmutex_boost,
+	.writeunlock	= torture_rtmutex_unlock,
+	.readlock       = NULL,
+	.read_delay     = NULL,
+	.readunlock     = NULL,
+	.name		= "rtmutex_lock"
+};
+#endif
+
 static DECLARE_RWSEM(torture_rwsem);
 static int torture_rwsem_down_write(void) __acquires(torture_rwsem)
 {
@@ -419,6 +518,7 @@ static void torture_rwsem_up_read(void) __releases(torture_rwsem)
 static struct lock_torture_ops rwsem_lock_ops = {
 	.writelock	= torture_rwsem_down_write,
 	.write_delay	= torture_rwsem_write_delay,
+	.task_boost     = torture_boost_dummy,
 	.writeunlock	= torture_rwsem_up_write,
 	.readlock       = torture_rwsem_down_read,
 	.read_delay     = torture_rwsem_read_delay,
@@ -442,6 +542,7 @@ static int lock_torture_writer(void *arg)
 		if ((torture_random(&rand) & 0xfffff) == 0)
 			schedule_timeout_uninterruptible(1);
 
+		cxt.cur_ops->task_boost(&rand);
 		cxt.cur_ops->writelock();
 		if (WARN_ON_ONCE(lock_is_write_held))
 			lwsp->n_lock_fail++;
@@ -456,6 +557,8 @@ static int lock_torture_writer(void *arg)
 
 		stutter_wait("lock_torture_writer");
 	} while (!torture_must_stop());
+
+	cxt.cur_ops->task_boost(NULL); /* reset prio */
 	torture_kthread_stopping("lock_torture_writer");
 	return 0;
 }
@@ -642,6 +745,9 @@ static int __init lock_torture_init(void)
 		&spin_lock_ops, &spin_lock_irq_ops,
 		&rw_lock_ops, &rw_lock_irq_ops,
 		&mutex_lock_ops,
+#ifdef CONFIG_RT_MUTEXES
+		&rtmutex_lock_ops,
+#endif
 		&rwsem_lock_ops,
 	};
 
@@ -676,6 +782,10 @@ static int __init lock_torture_init(void)
 	if (strncmp(torture_type, "mutex", 5) == 0)
 		cxt.debug_lock = true;
 #endif
+#ifdef CONFIG_DEBUG_RT_MUTEXES
+	if (strncmp(torture_type, "rtmutex", 7) == 0)
+		cxt.debug_lock = true;
+#endif
 #ifdef CONFIG_DEBUG_SPINLOCK
 	if ((strncmp(torture_type, "spin", 4) == 0) ||
 	    (strncmp(torture_type, "rw_lock", 7) == 0))
diff --git a/tools/testing/selftests/rcutorture/configs/lock/CFLIST b/tools/testing/selftests/rcutorture/configs/lock/CFLIST
index 6910b73..6ed3279 100644
--- a/tools/testing/selftests/rcutorture/configs/lock/CFLIST
+++ b/tools/testing/selftests/rcutorture/configs/lock/CFLIST
@@ -1,4 +1,5 @@
 LOCK01
 LOCK02
 LOCK03
-LOCK04
\ No newline at end of file
+LOCK04
+LOCK05
diff --git a/tools/testing/selftests/rcutorture/configs/lock/LOCK05 b/tools/testing/selftests/rcutorture/configs/lock/LOCK05
new file mode 100644
index 0000000..1d1da14
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/configs/lock/LOCK05
@@ -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/LOCK05.boot b/tools/testing/selftests/rcutorture/configs/lock/LOCK05.boot
new file mode 100644
index 0000000..8ac3730
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/configs/lock/LOCK05.boot
@@ -0,0 +1 @@
+locktorture.torture_type=rtmutex_lock
-- 
2.1.4

Re: [PATCH 2/2] locktorture: 'tis a slow death

[Paul E. McKenney]

On Thu, Jul 23, 2015 at 12:54:42PM -0700, Davidlohr Bueso wrote:
> On Wed, 2015-07-22 at 17:13 -0700, Paul E. McKenney wrote:
> > I need to see something more than what I am seeing for me to be able
> > to accept this, cute though it unarguably is.
> 
> heh I didn't consider copyright for this kind of stuff. And was naive to
> think that keeping his (what I assume to be) initials was enough. I've
> contacted the author for permission to use his work.
> 
> But yeah, I had to laugh when I saw this. Although I probably triggered
> some red flag by googling 'torture' and 'weapons' :-)

OK, once you get permission from the author to use under GPLv2, no
problem.

							Thanx, Paul