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SubjectRe: Why can't I set the priority of softirq-hrt? (Re: 2.6.17-rt1)
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Date
On Wed, 2006-06-21 at 16:43 +0100, Esben Nielsen wrote:
> What about the patch below. It compiles and my UP labtop runs fine, but I
> haven't otherwise tested it. My labtop runs RTExec without hichups
> until now.

NAK, it puts the burden into the lock path and also does a remove / add
which results in walking the chain twice.

Find an version against the code in -mm below. Not too much tested yet.

tglx

Index: linux-2.6.17-rc6-mm/kernel/rtmutex.c
===================================================================
--- linux-2.6.17-rc6-mm.orig/kernel/rtmutex.c 2006-06-21 13:34:34.000000000 +0200
+++ linux-2.6.17-rc6-mm/kernel/rtmutex.c 2006-06-21 15:45:21.000000000 +0200
@@ -160,7 +160,8 @@
static int rt_mutex_adjust_prio_chain(task_t *task,
int deadlock_detect,
struct rt_mutex *orig_lock,
- struct rt_mutex_waiter *orig_waiter)
+ struct rt_mutex_waiter *orig_waiter,
+ struct task_struct *top_task)
{
struct rt_mutex *lock;
struct rt_mutex_waiter *waiter, *top_waiter = orig_waiter;
@@ -188,7 +189,7 @@
prev_max = max_lock_depth;
printk(KERN_WARNING "Maximum lock depth %d reached "
"task: %s (%d)\n", max_lock_depth,
- current->comm, current->pid);
+ top_task->comm, top_task->pid);
}
put_task_struct(task);

@@ -228,7 +229,7 @@
}

/* Deadlock detection */
- if (lock == orig_lock || rt_mutex_owner(lock) == current) {
+ if (lock == orig_lock || rt_mutex_owner(lock) == top_task) {
debug_rt_mutex_deadlock(deadlock_detect, orig_waiter, lock);
spin_unlock(&lock->wait_lock);
ret = deadlock_detect ? -EDEADLK : 0;
@@ -448,7 +449,8 @@

spin_unlock(&lock->wait_lock);

- res = rt_mutex_adjust_prio_chain(owner, detect_deadlock, lock, waiter);
+ res = rt_mutex_adjust_prio_chain(owner, detect_deadlock, lock, waiter,
+ current);

spin_lock(&lock->wait_lock);

@@ -561,12 +563,35 @@

spin_unlock(&lock->wait_lock);

- rt_mutex_adjust_prio_chain(owner, 0, lock, NULL);
+ rt_mutex_adjust_prio_chain(owner, 0, lock, NULL, current);

spin_lock(&lock->wait_lock);
}

/*
+ * Recheck the pi chain, in case we got a priority setting
+ *
+ * Called from sched_setscheduler
+ */
+void rt_mutex_adjust_pi(struct task_struct *task)
+{
+ struct rt_mutex_waiter *waiter = task->pi_blocked_on;
+ unsigned long flags;
+
+ spin_lock_irqsave(&task->pi_lock, flags);
+
+ if (!waiter || waiter->list_entry.prio == task->prio) {
+ spin_unlock_irqrestore(&task->pi_lock, flags);
+ return;
+ }
+
+ get_task_struct(task);
+ spin_unlock_irqrestore(&task->pi_lock, flags);
+
+ rt_mutex_adjust_prio_chain(task, 0, NULL, NULL, task);
+}
+
+/*
* Slow path lock function:
*/
static int __sched
@@ -633,6 +658,7 @@
if (unlikely(ret))
break;
}
+
spin_unlock(&lock->wait_lock);

debug_rt_mutex_print_deadlock(&waiter);
Index: linux-2.6.17-rc6-mm/kernel/sched.c
===================================================================
--- linux-2.6.17-rc6-mm.orig/kernel/sched.c 2006-06-21 13:34:34.000000000 +0200
+++ linux-2.6.17-rc6-mm/kernel/sched.c 2006-06-21 18:21:16.000000000 +0200
@@ -4028,8 +4028,7 @@
int sched_setscheduler(struct task_struct *p, int policy,
struct sched_param *param)
{
- int retval;
- int oldprio, oldpolicy = -1;
+ int retval, oldprio, oldpolicy = -1;
prio_array_t *array;
unsigned long flags;
runqueue_t *rq;
@@ -4119,6 +4118,8 @@
__task_rq_unlock(rq);
spin_unlock_irqrestore(&p->pi_lock, flags);

+ rt_mutex_adjust_pi(p);
+
return 0;
}
EXPORT_SYMBOL_GPL(sched_setscheduler);
Index: linux-2.6.17-rc6-mm/include/linux/sched.h
===================================================================
--- linux-2.6.17-rc6-mm.orig/include/linux/sched.h 2006-06-21 13:37:21.000000000 +0200
+++ linux-2.6.17-rc6-mm/include/linux/sched.h 2006-06-21 15:43:23.000000000 +0200
@@ -1123,11 +1123,13 @@
#ifdef CONFIG_RT_MUTEXES
extern int rt_mutex_getprio(task_t *p);
extern void rt_mutex_setprio(task_t *p, int prio);
+extern void rt_mutex_adjust_pi(task_t *p);
#else
static inline int rt_mutex_getprio(task_t *p)
{
return p->normal_prio;
}
+# define rt_mutex_adjust_pi(p) do { } while (0)
#endif

extern void set_user_nice(task_t *p, long nice);

-
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