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Message-ID: <20150723001736.GI3717@linux.vnet.ibm.com>
Date: Wed, 22 Jul 2015 17:17:36 -0700
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: Davidlohr Bueso <dave@...olabs.net>
Cc: Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
linux-kernel@...r.kernel.org, Davidlohr Bueso <dbueso@...e.de>
Subject: Re: [PATCH 1/2] locktorture: Support rtmutex torturing
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@...e.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@...ibm.com>
> + * Authors: Paul E. McKenney <paulmck@...ibm.com>
> + * Davidlohr Bueso <dave@...olabs.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, ¶m);
> +}
> +
> +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
>
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