Re: PI patch against 2.6.16-rt9

Esben Nielsen
2006-03-27T23:06:04Z

On Mon, 27 Mar 2006, Esben Nielsen wrote:

> On Mon, 27 Mar 2006, Ingo Molnar wrote:
> [...]
> > nevertheless it _might_ work in practice, and it's certainly elegant and
> > thus tempting. Could you try to port your patch to -rt10? [you can skip
> > most of the conflicting rt7->rt10 deltas in rtmutex.c i think.]
> >
>
> I'll try to see what I can do. I am bit busy right now. We are packing to
> go to England for 4 months on Saturday. There are lot of practicalities
> we are still missing - but ofcourse PI code much more fun :-) Maybe I can
> "steal" some time tonight.
>

My girl friend will be angry for me not being to bed yet, but
I had to steal time to make this patch. I hope I managed to send it
without white-space damage or anything like it.

Esben

diff -upr linux-2.6.16-rt10/include/linux/rtmutex.h linux-2.6.16-rt10.pipatch/include/linux/rtmutex.h
--- linux-2.6.16-rt10/include/linux/rtmutex.h 2006-03-28 00:47:05.000000000 +0200
+++ linux-2.6.16-rt10.pipatch/include/linux/rtmutex.h 2006-03-27 18:40:08.000000000 +0200
@@ -107,8 +107,7 @@ extern void rt_mutex_unlock(struct rt_mu
#ifdef CONFIG_RT_MUTEXES
# define INIT_RT_MUTEXES(tsk) \
.pi_waiters = PLIST_HEAD_INIT(tsk.pi_waiters, tsk.pi_lock), \
- .pi_lock = RAW_SPIN_LOCK_UNLOCKED, \
- .pi_lock_chain = LIST_HEAD_INIT(tsk.pi_lock_chain),
+ .pi_lock = RAW_SPIN_LOCK_UNLOCKED,
#else
# define INIT_RT_MUTEXES(tsk)
#endif
diff -upr linux-2.6.16-rt10/include/linux/sched.h linux-2.6.16-rt10.pipatch/include/linux/sched.h
--- linux-2.6.16-rt10/include/linux/sched.h 2006-03-28 00:47:05.000000000 +0200
+++ linux-2.6.16-rt10.pipatch/include/linux/sched.h 2006-03-27 18:40:08.000000000 +0200
@@ -985,9 +985,6 @@ struct task_struct {
struct plist_head pi_waiters;
/* Deadlock detection and priority inheritance handling */
struct rt_mutex_waiter *pi_blocked_on;
- /* PI locking helpers */
- struct task_struct *pi_locked_by;
- struct list_head pi_lock_chain;
#endif

#ifdef CONFIG_DEBUG_MUTEXES
diff -upr linux-2.6.16-rt10/include/linux/spinlock_api_smp.h linux-2.6.16-rt10.pipatch/include/linux/spinlock_api_smp.h
--- linux-2.6.16-rt10/include/linux/spinlock_api_smp.h 2006-03-28 00:47:05.000000000 +0200
+++ linux-2.6.16-rt10.pipatch/include/linux/spinlock_api_smp.h 2006-03-27 18:40:08.000000000 +0200
@@ -39,6 +39,7 @@ int __lockfunc _raw_read_trylock(raw_rwl
int __lockfunc _raw_write_trylock(raw_rwlock_t *lock);
int __lockfunc _raw_spin_trylock_irqsave(raw_spinlock_t *lock,
unsigned long *flags);
+int __lockfunc _raw_spin_trylock_irq(raw_spinlock_t *lock);
int __lockfunc _raw_spin_trylock_bh(raw_spinlock_t *lock);
void __lockfunc _raw_spin_unlock(raw_spinlock_t *lock) __releases(raw_spinlock_t);
void __lockfunc _raw_spin_unlock_no_resched(raw_spinlock_t *lock) __releases(raw_spinlock_t);
diff -upr linux-2.6.16-rt10/include/linux/spinlock_api_up.h linux-2.6.16-rt10.pipatch/include/linux/spinlock_api_up.h
--- linux-2.6.16-rt10/include/linux/spinlock_api_up.h 2006-03-28 00:47:05.000000000 +0200
+++ linux-2.6.16-rt10.pipatch/include/linux/spinlock_api_up.h 2006-03-27 18:40:08.000000000 +0200
@@ -39,6 +39,9 @@
#define __TRYLOCK_IRQSAVE(lock, flags) \
({ local_irq_save(*(flags)); __LOCK(lock); 1; })

+#define __TRYLOCK_IRQ(lock) \
+ ({ raw_local_irq_disable(); __LOCK(lock); 1; })
+
#define _raw_spin_trylock_irqsave(lock, flags) __TRYLOCK_IRQSAVE(lock, flags)

#define __UNLOCK(lock) \
@@ -75,6 +78,7 @@
#define _raw_read_trylock_bh(lock) ({ __LOCK_BH(lock); 1; })
#define _raw_write_trylock_bh(lock) ({ __LOCK_BH(lock); 1; })
#define _raw_spin_trylock_irqsave(lock, flags) __TRYLOCK_IRQSAVE(lock, flags)
+#define _raw_spin_trylock_irq(lock) __TRYLOCK_IRQ(lock)
#define _raw_read_trylock_irqsave(lock, flags) __TRYLOCK_IRQSAVE(lock, flags)
#define _raw_read_trylock_irqsave(lock, flags) __TRYLOCK_IRQSAVE(lock, flags)
#define _raw_spin_unlock(lock) __UNLOCK(lock)
diff -upr linux-2.6.16-rt10/include/linux/sysctl.h linux-2.6.16-rt10.pipatch/include/linux/sysctl.h
--- linux-2.6.16-rt10/include/linux/sysctl.h 2006-03-20 06:53:29.000000000 +0100
+++ linux-2.6.16-rt10.pipatch/include/linux/sysctl.h 2006-03-27 18:40:08.000000000 +0200
@@ -148,6 +148,7 @@ enum
KERN_SPIN_RETRY=70, /* int: number of spinlock retries */
KERN_ACPI_VIDEO_FLAGS=71, /* int: flags for setting up video after ACPI sleep */
KERN_IA64_UNALIGNED=72, /* int: ia64 unaligned userland trap enable */
+ KERN_MAX_LOCK_DEPTH=73
};

diff -upr linux-2.6.16-rt10/kernel/fork.c linux-2.6.16-rt10.pipatch/kernel/fork.c
--- linux-2.6.16-rt10/kernel/fork.c 2006-03-28 00:47:05.000000000 +0200
+++ linux-2.6.16-rt10.pipatch/kernel/fork.c 2006-03-27 18:40:08.000000000 +0200
@@ -947,8 +947,6 @@ static inline void rt_mutex_init_task(st
spin_lock_init(&p->pi_lock);
plist_head_init(&p->pi_waiters, &p->pi_lock);
p->pi_blocked_on = NULL;
- p->pi_locked_by = NULL;
- INIT_LIST_HEAD(&p->pi_lock_chain);
#endif
}

diff -upr linux-2.6.16-rt10/kernel/rtmutex-debug.c linux-2.6.16-rt10.pipatch/kernel/rtmutex-debug.c
--- linux-2.6.16-rt10/kernel/rtmutex-debug.c 2006-03-28 00:47:05.000000000 +0200
+++ linux-2.6.16-rt10.pipatch/kernel/rtmutex-debug.c 2006-03-27 18:40:08.000000000 +0200
@@ -398,9 +398,7 @@ restart:
void notrace rt_mutex_debug_task_free(struct task_struct *tsk)
{
WARN_ON(!plist_head_empty(&tsk->pi_waiters));
- WARN_ON(!list_empty(&tsk->pi_lock_chain));
WARN_ON(tsk->pi_blocked_on);
- WARN_ON(tsk->pi_locked_by);
}

/*
diff -upr linux-2.6.16-rt10/kernel/rtmutex.c linux-2.6.16-rt10.pipatch/kernel/rtmutex.c
--- linux-2.6.16-rt10/kernel/rtmutex.c 2006-03-28 00:47:05.000000000 +0200
+++ linux-2.6.16-rt10.pipatch/kernel/rtmutex.c 2006-03-28 00:11:24.000000000 +0200
@@ -160,204 +160,103 @@ static void rt_mutex_adjust_prio(struct
spin_unlock_irqrestore(&task->pi_lock, flags);
}

-/*
- * PI-locking: we lock PI-dependencies opportunistically via trylock.
- *
- * In the overwhelming majority of cases the 'PI chain' is empty or at
- * most 1-2 entries long, for which the trylock is sufficient,
- * scalability-wise. The locking might look a bit scary, for which we
- * apologize in advance :-)
- *
- * If any of the trylocks fails then we back out, task the global
- * pi_conflicts_lock and take the locks again. This ensures deadlock-free
- * but still scalable locking in the dependency graph, combined with
- * the ability to reliably (and cheaply) detect user-space deadlocks.
- */
-static DEFINE_RAW_SPINLOCK(pi_conflicts_lock);

-/*
- * Lock the full boosting chain.
- *
- * If 'try' is set, we have to backout if we hit a owner who is
- * running its own pi chain operation. We go back and take the slow
- * path via the pi_conflicts_lock.
- *
- * We put all held locks into a list, via ->pi_lock_chain, and walk
- * this list at unlock_pi_chain() time.
- */
-static int lock_pi_chain(struct rt_mutex *act_lock,
- struct rt_mutex_waiter *waiter,
- struct list_head *lock_chain,
- int try, int detect_deadlock)
-{
- struct task_struct *owner;
- struct rt_mutex *nextlock, *lock = act_lock;
- struct rt_mutex_waiter *nextwaiter;
- int deadlock_detect;
+int max_lock_depth = 100;

- /*
- * Debugging might turn deadlock detection on, unconditionally:
- */
- deadlock_detect = debug_rt_mutex_detect_deadlock(detect_deadlock);
+/*
+ * Adjust the priority chain. Also used for deadlock detection.
+ * Decreases task's usage by one - may thus free the task.
+ * Returns 0 or -EDEADLK.
+ */
+static int rt_mutex_adjust_prio_chain(task_t *task,
+ int deadlock_detect,
+ struct rt_mutex_waiter *orig_waiter
+ __IP_DECL__)
+{
+ struct rt_mutex *lock = orig_waiter->lock;
+ struct rt_mutex_waiter *waiter, *top_waiter;
+ task_t *owner;
+ unsigned long flags;

- for (;;) {
- owner = rt_mutex_owner(lock);
+ int detect_deadlock, ret = 0, depth = 0;

- /* Check for circular dependencies */
- if (unlikely(owner->pi_locked_by == current)) {
- debug_rt_mutex_deadlock(detect_deadlock, waiter, lock);
- return detect_deadlock ? -EDEADLK : 1;
- }
+ detect_deadlock = debug_rt_mutex_detect_deadlock(deadlock_detect);

- while (!spin_trylock(&owner->pi_lock)) {
- /*
- * Owner runs its own chain. Go back and take
- * the slow path
- */
- if (try && owner->pi_locked_by == owner)
- return -EBUSY;
- cpu_relax();
+ for (;;) {
+ depth++;
+ if(task==current || depth>max_lock_depth) {
+ debug_rt_mutex_deadlock(deadlock_detect,
+ orig_waiter, lock);
+
+ put_task_struct(task);
+
+ return deadlock_detect ? -EDEADLK : 0;
}
+ retry:
+ _raw_spin_lock(&task->pi_lock);
+ __rt_mutex_adjust_prio(task);
+ waiter = task->pi_blocked_on;
+ if( !waiter )
+ break;

- BUG_ON(owner->pi_locked_by);
- owner->pi_locked_by = current;
- BUG_ON(!list_empty(&owner->pi_lock_chain));
- list_add(&owner->pi_lock_chain, lock_chain);
-
- /*
- * When the owner is blocked on a lock, try to take
- * the lock:
- */
- nextwaiter = owner->pi_blocked_on;
-
- /* End of chain? */
- if (!nextwaiter)
- return 1;
-
- nextlock = nextwaiter->lock;
-
- /* Check for circular dependencies: */
- if (unlikely(nextlock == act_lock ||
- rt_mutex_owner(nextlock) == current)) {
- debug_rt_mutex_deadlock(detect_deadlock, waiter,
- nextlock);
- list_del_init(&owner->pi_lock_chain);
- owner->pi_locked_by = NULL;
- spin_unlock(&owner->pi_lock);
- return detect_deadlock ? -EDEADLK : 1;
- }
+ if( !detect_deadlock &&
+ waiter->list_entry.prio == task->prio &&
+ waiter->pi_list_entry.prio == waiter->list_entry.prio )
+ break;

- /* Try to get nextlock->wait_lock: */
- if (unlikely(!spin_trylock(&nextlock->wait_lock))) {
- list_del_init(&owner->pi_lock_chain);
- owner->pi_locked_by = NULL;
- spin_unlock(&owner->pi_lock);
+
+ lock = waiter->lock;
+ if( !spin_trylock_irqsave(&lock->wait_lock, flags) ) {
+ _raw_spin_unlock(&task->pi_lock);
cpu_relax();
- continue;
+ goto retry;
}

- lock = nextlock;
-
- /*
- * If deadlock detection is done (or has to be done, as
- * for userspace locks), we have to walk the full chain
- * unconditionally.
- */
- if (deadlock_detect)
- continue;
+ top_waiter = rt_mutex_top_waiter(lock);

- /*
- * Optimization: we only have to continue up to the point
- * where boosting/unboosting still has to be done:
- */
+ plist_del(&waiter->list_entry, &lock->wait_list);
+ waiter->list_entry.prio = task->prio;
+ plist_add(&waiter->list_entry, &lock->wait_list);
+
+ _raw_spin_unlock(&task->pi_lock);

- /* Boost or unboost? */
- if (waiter) {
- /* If the top waiter has higher priority, stop: */
- if (rt_mutex_top_waiter(lock)->list_entry.prio <=
- waiter->list_entry.prio)
- return 1;
- } else {
- /* If nextwaiter is not the top waiter, stop: */
- if (rt_mutex_top_waiter(lock) != nextwaiter)
- return 1;
+ owner = rt_mutex_owner(lock);
+ BUG_ON(!owner);
+ BUG_ON(owner==task);
+ if(waiter == rt_mutex_top_waiter(lock)) {
+ _raw_spin_lock(&owner->pi_lock);
+ plist_del(&top_waiter->pi_list_entry,
+ &owner->pi_waiters);
+
+ waiter->pi_list_entry.prio = waiter->list_entry.prio;
+ plist_add(&waiter->pi_list_entry, &owner->pi_waiters);
+ _raw_spin_unlock(&owner->pi_lock);
}
- }
-}
-
-/*
- * Unlock the pi_chain:
- */
-static void unlock_pi_chain(struct list_head *lock_chain)
-{
- struct task_struct *owner, *tmp;
-
- list_for_each_entry_safe(owner, tmp, lock_chain, pi_lock_chain) {
- struct rt_mutex_waiter *waiter = owner->pi_blocked_on;
-
- list_del_init(&owner->pi_lock_chain);
- BUG_ON(!owner->pi_locked_by);
- owner->pi_locked_by = NULL;
- if (waiter)
- spin_unlock(&waiter->lock->wait_lock);
- spin_unlock(&owner->pi_lock);
- }
-}
-
-/*
- * Do the priority (un)boosting along the chain:
- */
-static void adjust_pi_chain(struct rt_mutex *lock,
- struct rt_mutex_waiter *waiter,
- struct rt_mutex_waiter *top_waiter,
- struct list_head *lock_chain)
-{
- struct task_struct *owner = rt_mutex_owner(lock);
- struct list_head *curr = lock_chain->prev;
-
- for (;;) {
- if (top_waiter)
- plist_del(&top_waiter->pi_list_entry,
+ else if(top_waiter == waiter) {
+ /* waiter is no longer the frontmost waiter */
+ _raw_spin_lock(&owner->pi_lock);
+ plist_del(&waiter->pi_list_entry,
&owner->pi_waiters);
-
- if (waiter)
- waiter->pi_list_entry.prio = waiter->task->prio;
-
- if (rt_mutex_has_waiters(lock)) {
top_waiter = rt_mutex_top_waiter(lock);
- plist_add(&top_waiter->pi_list_entry,
+ top_waiter->pi_list_entry.prio =
+ top_waiter->list_entry.prio;
+ plist_add(&top_waiter->pi_list_entry,
&owner->pi_waiters);
+ _raw_spin_unlock(&owner->pi_lock);
}

- __rt_mutex_adjust_prio(owner);

- waiter = owner->pi_blocked_on;
- if (!waiter || curr->prev == lock_chain)
- return;
+ get_task_struct(owner);

- curr = curr->prev;
- lock = waiter->lock;
- owner = rt_mutex_owner(lock);
- top_waiter = rt_mutex_top_waiter(lock);
+ spin_unlock_irqrestore(&lock->wait_lock,flags);

- plist_del(&waiter->list_entry, &lock->wait_list);
- waiter->list_entry.prio = waiter->task->prio;
- plist_add(&waiter->list_entry, &lock->wait_list);
-
- /*
- * We can stop here, if the waiter is/was not the top
- * priority waiter:
- */
- if (top_waiter != waiter &&
- waiter != rt_mutex_top_waiter(lock))
- return;
-
- /*
- * Note: waiter is not necessarily the new top
- * waiter!
- */
- waiter = rt_mutex_top_waiter(lock);
+ put_task_struct(task);
+ task = owner;
}
+
+ _raw_spin_unlock(&task->pi_lock);
+ put_task_struct(task);
+ return ret;
}

/*
@@ -468,111 +367,63 @@ static int try_to_take_rt_mutex(struct r
/*
* Task blocks on lock.
*
- * Prepare waiter and potentially propagate our priority into the pi chain.
+ * Prepare waiter and propagate pi chain
*
* This must be called with lock->wait_lock held.
- * return values: 1: waiter queued, 0: got the lock,
- * -EDEADLK: deadlock detected.
+ *
+ * Returns owner if it is needed to be boosted with adjust_prio_chain() if
+ * it is in itself blocked on a lock.
*/
-static int task_blocks_on_rt_mutex(struct rt_mutex *lock,
- struct rt_mutex_waiter *waiter,
- int detect_deadlock __IP_DECL__)
+static task_t *task_blocks_on_rt_mutex(struct rt_mutex *lock,
+ struct rt_mutex_waiter *waiter,
+ int detect_deadlock
+ __IP_DECL__)
{
struct rt_mutex_waiter *top_waiter = waiter;
- LIST_HEAD(lock_chain);
- int res = 1;
+ task_t *owner = rt_mutex_owner(lock);
+ task_t *res = NULL;

+ _raw_spin_lock(&current->pi_lock);
+ __rt_mutex_adjust_prio(current);
waiter->task = current;
waiter->lock = lock;
- debug_rt_mutex_reset_waiter(waiter);
-
- spin_lock(&current->pi_lock);
- current->pi_locked_by = current;
plist_node_init(&waiter->list_entry, current->prio);
plist_node_init(&waiter->pi_list_entry, current->prio);

- /* Get the top priority waiter of the lock: */
+ /* Get the top priority waiter on the lock */
if (rt_mutex_has_waiters(lock))
top_waiter = rt_mutex_top_waiter(lock);
plist_add(&waiter->list_entry, &lock->wait_list);

current->pi_blocked_on = waiter;

- /*
- * Call adjust_prio_chain, when waiter is the new top waiter
- * or when deadlock detection is requested:
- */
- if (waiter != rt_mutex_top_waiter(lock) &&
- !debug_rt_mutex_detect_deadlock(detect_deadlock))
- goto out_unlock_pi;
-
- /* Try to lock the full chain: */
- res = lock_pi_chain(lock, waiter, &lock_chain, 1, detect_deadlock);
-
- if (likely(res == 1))
- adjust_pi_chain(lock, waiter, top_waiter, &lock_chain);
-
- /* Common case: we managed to lock it: */
- if (res != -EBUSY)
- goto out_unlock_chain_pi;
+ _raw_spin_unlock(&current->pi_lock);

- /* Rare case: we hit some other task running a pi chain operation: */
- unlock_pi_chain(&lock_chain);
-
- plist_del(&waiter->list_entry, &lock->wait_list);
- current->pi_blocked_on = NULL;
- current->pi_locked_by = NULL;
- spin_unlock(&current->pi_lock);
- fixup_rt_mutex_waiters(lock);
-
- spin_unlock(&lock->wait_lock);
-
- /*
- * Here we have dropped all locks, and take the global
- * pi_conflicts_lock. We have to redo all the work, no
- * previous information about the lock is valid anymore:
- */
- spin_lock(&pi_conflicts_lock);
+ if (waiter == rt_mutex_top_waiter(lock)) {
+ _raw_spin_lock(&owner->pi_lock);
+ plist_del(&top_waiter->pi_list_entry, &owner->pi_waiters);
+ plist_add(&waiter->pi_list_entry, &owner->pi_waiters);
+
+ __rt_mutex_adjust_prio(owner);
+ if(owner->pi_blocked_on) {
+ /* Nested locks. We do the boosting of the next
+ tasks just before going to sleep in schedule */
+ res = owner;
+ get_task_struct(owner);
+ }

- spin_lock(&lock->wait_lock);
- if (try_to_take_rt_mutex(lock __IP__)) {
- /*
- * Rare race: against all odds we got the lock.
- */
- res = 0;
- goto out;
+ _raw_spin_unlock(&owner->pi_lock);
+ }
+ else if( debug_rt_mutex_detect_deadlock(detect_deadlock) ) {
+ _raw_spin_lock(&owner->pi_lock);
+ if(owner->pi_blocked_on) {
+ res = owner;
+ get_task_struct(owner);
+ }
+ _raw_spin_unlock(&owner->pi_lock);
}

- WARN_ON(!rt_mutex_owner(lock) || rt_mutex_owner(lock) == current);
-
- spin_lock(&current->pi_lock);
- current->pi_locked_by = current;
-
- plist_node_init(&waiter->list_entry, current->prio);
- plist_node_init(&waiter->pi_list_entry, current->prio);
-
- /* Get the top priority waiter of the lock: */
- if (rt_mutex_has_waiters(lock))
- top_waiter = rt_mutex_top_waiter(lock);
- plist_add(&waiter->list_entry, &lock->wait_list);
-
- current->pi_blocked_on = waiter;
-
- /* Lock the full chain: */
- res = lock_pi_chain(lock, waiter, &lock_chain, 0, detect_deadlock);
-
- /* Drop the conflicts lock before adjusting: */
- spin_unlock(&pi_conflicts_lock);
-
- if (likely(res == 1))
- adjust_pi_chain(lock, waiter, top_waiter, &lock_chain);

- out_unlock_chain_pi:
- unlock_pi_chain(&lock_chain);
- out_unlock_pi:
- current->pi_locked_by = NULL;
- spin_unlock(&current->pi_lock);
- out:
return res;
}

@@ -639,87 +490,49 @@ static void wakeup_next_waiter(struct rt
/*
* Remove a waiter from a lock
*
- * Must be called with lock->wait_lock held.
+ * Must be called with lock->wait_lock held
*/
-static int remove_waiter(struct rt_mutex *lock,
- struct rt_mutex_waiter *waiter __IP_DECL__)
+static task_t *remove_waiter(struct rt_mutex *lock,
+ struct rt_mutex_waiter *waiter __IP_DECL__)
{
- struct rt_mutex_waiter *next_waiter = NULL,
- *top_waiter = rt_mutex_top_waiter(lock);
- LIST_HEAD(lock_chain);
- int res;
+ int first = (waiter == rt_mutex_top_waiter(lock));
+ task_t *res = NULL;

plist_del(&waiter->list_entry, &lock->wait_list);

- spin_lock(&current->pi_lock);
-
- if (waiter != top_waiter || rt_mutex_owner(lock) == current)
- goto out;
-
- current->pi_locked_by = current;

- if (rt_mutex_has_waiters(lock))
- next_waiter = rt_mutex_top_waiter(lock);
+ if (first && rt_mutex_owner(lock) != current) {
+ task_t *owner = rt_mutex_owner(lock);

- /* Try to lock the full chain: */
- res = lock_pi_chain(lock, next_waiter, &lock_chain, 1, 0);
+ _raw_spin_lock(&owner->pi_lock);

- if (likely(res != -EBUSY)) {
- adjust_pi_chain(lock, next_waiter, waiter, &lock_chain);
- goto out_unlock;
- }
+ plist_del(&waiter->pi_list_entry, &owner->pi_waiters);

- /* We hit some other task running a pi chain operation: */
- unlock_pi_chain(&lock_chain);
- plist_add(&waiter->list_entry, &lock->wait_list);
- current->pi_blocked_on = waiter;
- current->pi_locked_by = NULL;
- spin_unlock(&current->pi_lock);
- spin_unlock(&lock->wait_lock);
-
- spin_lock(&pi_conflicts_lock);
+ if (rt_mutex_has_waiters(lock)) {
+ struct rt_mutex_waiter *next;

- spin_lock(&lock->wait_lock);
+ next = rt_mutex_top_waiter(lock);
+ plist_add(&next->pi_list_entry, &owner->pi_waiters);
+ }

- spin_lock(&current->pi_lock);
- current->pi_locked_by = current;

- /* We might have been woken up: */
- if (!waiter->task) {
- spin_unlock(&pi_conflicts_lock);
- goto out;
+ __rt_mutex_adjust_prio(owner);
+ if(owner->pi_blocked_on) {
+ /* Owner is blocked on something - we have
+ to (un)boost throughout the lock chain but
+ we have to wait until we have dropped all locks */
+ res = owner;
+ get_task_struct(owner);
+ }
+ _raw_spin_unlock(&owner->pi_lock);
}

- top_waiter = rt_mutex_top_waiter(lock);
-
- plist_del(&waiter->list_entry, &lock->wait_list);
-
- if (waiter != top_waiter || rt_mutex_owner(lock) == current)
- goto out;
-
- /* Get the top priority waiter of the lock: */
- if (rt_mutex_has_waiters(lock))
- next_waiter = rt_mutex_top_waiter(lock);
-
- /* Lock the full chain: */
- lock_pi_chain(lock, next_waiter, &lock_chain, 0, 0);
-
- /* Drop the conflicts lock: */
- spin_unlock(&pi_conflicts_lock);
-
- adjust_pi_chain(lock, next_waiter, waiter, &lock_chain);
+ WARN_ON(!plist_node_empty(&waiter->pi_list_entry));

- out_unlock:
- unlock_pi_chain(&lock_chain);
- out:
current->pi_blocked_on = NULL;
waiter->task = NULL;
- current->pi_locked_by = NULL;
- spin_unlock(&current->pi_lock);

- WARN_ON(!plist_node_empty(&waiter->pi_list_entry));
-
- return 0;
+ return res;
}

#ifdef CONFIG_PREEMPT_RT
@@ -759,6 +572,7 @@ rt_lock_slowlock(struct rt_mutex *lock _
{
struct rt_mutex_waiter waiter;
unsigned long saved_state, state, flags;
+ task_t *owner;

debug_rt_mutex_init_waiter(&waiter);
waiter.task = NULL;
@@ -788,7 +602,7 @@ rt_lock_slowlock(struct rt_mutex *lock _

for (;;) {
unsigned long saved_flags;
- int ret, saved_lock_depth = current->lock_depth;
+ int saved_lock_depth = current->lock_depth;

/* Try to acquire the lock */
if (try_to_take_rt_mutex(lock __IP__))
@@ -798,12 +612,25 @@ rt_lock_slowlock(struct rt_mutex *lock _
* when we have been woken up by the previous owner
* but the lock got stolen by an higher prio task.
*/
- if (!waiter.task) {
- ret = task_blocks_on_rt_mutex(lock, &waiter, 0 __IP__);
- /* got the lock or deadlock: */
- if (ret == 0 || ret == -EDEADLK)
- break;
+ if (!waiter.task)
+ owner = task_blocks_on_rt_mutex(lock, &waiter, 0
+ __IP__);
+ else
+ owner = NULL;
+
+ if (unlikely(owner)) {
+ spin_unlock_irqrestore(&lock->wait_lock,flags);
+ rt_mutex_adjust_prio_chain(owner, 0, &waiter __IP__);
+ owner = NULL;
+ spin_lock_irqsave(&lock->wait_lock,flags);
+ if(unlikely(!waiter.task))
+ continue; /* We got woken up by the owner
+ * Start loop all over without
+ * going into schedule to try
+ * to get the lock now
+ */
}
+

/*
* Prevent schedule() to drop BKL, while waiting for
@@ -838,7 +665,9 @@ rt_lock_slowlock(struct rt_mutex *lock _
* can end up with a non-NULL waiter.task:
*/
if (unlikely(waiter.task))
- remove_waiter(lock, &waiter __IP__);
+ owner = remove_waiter(lock, &waiter __IP__);
+ else
+ owner = NULL;
/*
* try_to_take_rt_mutex() sets the waiter bit
* unconditionally. We might have to fix that up:
@@ -847,6 +676,9 @@ rt_lock_slowlock(struct rt_mutex *lock _

spin_unlock_irqrestore(&lock->wait_lock, flags);

+ if (unlikely(owner))
+ rt_mutex_adjust_prio_chain(owner, 0, &waiter __IP__);
+
debug_rt_mutex_free_waiter(&waiter);
}

@@ -936,6 +768,7 @@ rt_mutex_slowlock(struct rt_mutex *lock,
struct rt_mutex_waiter waiter;
int ret = 0, saved_lock_depth = -1;
unsigned long flags;
+ task_t *owner;

debug_rt_mutex_init_waiter(&waiter);
waiter.task = NULL;
@@ -950,8 +783,6 @@ rt_mutex_slowlock(struct rt_mutex *lock,
return 0;
}

- BUG_ON(rt_mutex_owner(lock) == current);
-
/*
* We drop BKL here before we go into the wait loop to avoid a
* possible deadlock in the scheduler.
@@ -992,15 +823,31 @@ rt_mutex_slowlock(struct rt_mutex *lock,
* when we have been woken up by the previous owner
* but the lock got stolen by an higher prio task.
*/
- if (!waiter.task) {
- ret = task_blocks_on_rt_mutex(lock, &waiter,
+ if (!waiter.task)
+ owner = task_blocks_on_rt_mutex(lock, &waiter,
detect_deadlock __IP__);
- /* got the lock or deadlock: */
- if (ret == 0 || ret == -EDEADLK)
+ else
+ owner = NULL;
+
+ if (unlikely(owner)) {
+ spin_unlock_irqrestore(&lock->wait_lock,flags);
+ ret = rt_mutex_adjust_prio_chain(owner,
+ detect_deadlock,
+ &waiter __IP__);
+ owner = NULL;
+ spin_lock_irqsave(&lock->wait_lock,flags);
+
+ if (unlikely(ret))
break;
- ret = 0;
- }

+ if (unlikely(!waiter.task))
+ continue; /* We got woken up by the owner
+ * Start loop all over without
+ * going into schedule to try
+ * to get the lock now
+ */
+ }
+
saved_flags = current->flags & PF_NOSCHED;
current->flags &= ~PF_NOSCHED;

@@ -1019,8 +866,10 @@ rt_mutex_slowlock(struct rt_mutex *lock,

set_current_state(TASK_RUNNING);

- if (unlikely(waiter.task))
- remove_waiter(lock, &waiter __IP__);
+ if (unlikely(waiter.task))
+ owner = remove_waiter(lock, &waiter __IP__);
+ else
+ owner = NULL;

/*
* try_to_take_rt_mutex() sets the waiter bit
@@ -1030,6 +879,9 @@ rt_mutex_slowlock(struct rt_mutex *lock,

spin_unlock_irqrestore(&lock->wait_lock, flags);

+ if (unlikely(owner))
+ rt_mutex_adjust_prio_chain(owner, 0, &waiter __IP__);
+
/* Remove pending timer: */
if (unlikely(timeout && timeout->task))
hrtimer_cancel(&timeout->timer);
Only in linux-2.6.16-rt10.pipatch/kernel: rtmutex.c.orig
Only in linux-2.6.16-rt10.pipatch/kernel: rtmutex.c.rej
Only in linux-2.6.16-rt10.pipatch/kernel: rtmutex.c~
diff -upr linux-2.6.16-rt10/kernel/sysctl.c linux-2.6.16-rt10.pipatch/kernel/sysctl.c
--- linux-2.6.16-rt10/kernel/sysctl.c 2006-03-28 00:47:05.000000000 +0200
+++ linux-2.6.16-rt10.pipatch/kernel/sysctl.c 2006-03-27 18:40:08.000000000 +0200
@@ -132,6 +132,10 @@ extern int acct_parm[];
extern int no_unaligned_warning;
#endif

+#ifdef CONFIG_RT_MUTEXES
+extern int max_lock_depth;
+#endif
+
static int parse_table(int __user *, int, void __user *, size_t __user *, void __user *, size_t,
ctl_table *, void **);
static int proc_doutsstring(ctl_table *table, int write, struct file *filp,
@@ -827,6 +831,17 @@ static ctl_table kern_table[] = {
.proc_handler = &proc_dointvec,
},
#endif
+#ifdef CONFIG_RT_MUTEXES
+ {
+ .ctl_name = KERN_MAX_LOCK_DEPTH,
+ .procname = "max_lock_depth",
+ .data = &max_lock_depth,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = &proc_dointvec,
+ },
+#endif
+
{ .ctl_name = 0 }
};

diff -upr linux-2.6.16-rt10/scripts/rt-tester/t3-l1-pi-signal.tst linux-2.6.16-rt10.pipatch/scripts/rt-tester/t3-l1-pi-signal.tst
--- linux-2.6.16-rt10/scripts/rt-tester/t3-l1-pi-signal.tst 2006-03-28 00:47:05.000000000 +0200
+++ linux-2.6.16-rt10.pipatch/scripts/rt-tester/t3-l1-pi-signal.tst 2006-03-27 18:40:08.000000000 +0200
@@ -69,15 +69,18 @@ W: locked: 0: 0
C: locknowait: 1: 0
W: blocked: 1: 0
T: prioeq: 0: 80
+T: prioeq: 1: 80

# T2 lock L0 interruptible, no wait in the wakeup path
C: lockintnowait: 2: 0
W: blocked: 2: 0
T: prioeq: 0: 81
+T: prioeq: 1: 80

# Interrupt T2
C: signal: 2: 2
W: unlocked: 2: 0
+T: prioeq: 1: 80
T: prioeq: 0: 80

T: locked: 0: 0

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