Re: Why can't I set the priority of softirq-hrt? (Re: 2.6.17-rt1)

[Steven Rostedt]

On Wed, 21 Jun 2006, Esben Nielsen wrote:

> > Yeah, I saw. Move it out in setscheduler() then. I'll try to fix it, but I am
> > not sure I can make a test if it works.
>
> 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.

Hm, I take it that English is not your native language (maybe it its??)
You do write very well regardless, but I notice with my German colleagues,
that they seem to always translate "bis jetzt" to "until now" when I would
use something like "as of yet".  The "until now" (at least to me) gives
the impression that it hasn't happened up till now, but it has happended
now.  So one could say after running their car into a tree "Oh well,
I haven't had an accident until now". So I'm assuming that you still don't
have hichups.
  OK enough about that ;)

The below patch has whitespace damage.  Could you resend?

Thanks,

-- Steve

>
> Esben
>
> Index: linux-2.6.17-rt1/kernel/rtmutex.c
> ===================================================================
> --- linux-2.6.17-rt1.orig/kernel/rtmutex.c
> +++ linux-2.6.17-rt1/kernel/rtmutex.c
> @@ -625,6 +625,7 @@ rt_lock_slowlock(struct rt_mutex *lock _
>
>   	debug_rt_mutex_init_waiter(&waiter);
>   	waiter.task = NULL;
> +	waiter.save_state = 1;
>
>   	spin_lock(&lock->wait_lock);
>
> @@ -687,6 +688,19 @@ rt_lock_slowlock(struct rt_mutex *lock _
>   		state = xchg(&current->state, TASK_UNINTERRUPTIBLE);
>   		if (unlikely(state == TASK_RUNNING))
>   			saved_state = TASK_RUNNING;
> +
> +		if (unlikely(waiter.task) &&
> +		    waiter.list_entry.prio != current->prio) {
> +			/*
> +			 * We still not have the lock, but we are woken up with
> +			 * a different prio than the one we waited with
> +			 * originally. We remove the wait entry now and then
> +			 * reinsert ourselves with the right priority
> +			 */
> +			remove_waiter(lock, &waiter __IP__);
> +			waiter.task = NULL;
> +		}
> +
>   	}
>
>   	state = xchg(&current->state, saved_state);
> @@ -798,6 +812,7 @@ rt_mutex_slowlock(struct rt_mutex *lock,
>
>   	debug_rt_mutex_init_waiter(&waiter);
>   	waiter.task = NULL;
> +	waiter.save_state = 0;
>
>   	spin_lock(&lock->wait_lock);
>
> @@ -877,6 +892,18 @@ rt_mutex_slowlock(struct rt_mutex *lock,
>
>   		current->flags |= saved_flags;
>   		set_current_state(state);
> +
> +		if (unlikely(waiter.task) &&
> +		    waiter.list_entry.prio != current->prio) {
> +			/*
> +			 * We still not have the lock, but we are woken up with
> +			 * a different prio than the one we waited with
> +			 * originally. We remove the wait entry now and then
> +			 * reinsert ourselves with the right priority
> +			 */
> +			remove_waiter(lock, &waiter __IP__);
> +			waiter.task = NULL;
> +		}
>   	}
>
>   	set_current_state(TASK_RUNNING);
> Index: linux-2.6.17-rt1/kernel/sched.c
> ===================================================================
> --- linux-2.6.17-rt1.orig/kernel/sched.c
> +++ linux-2.6.17-rt1/kernel/sched.c
> @@ -57,6 +57,8 @@
>
>   #include <asm/unistd.h>
>
> +#include "rtmutex_common.h"
> +
>   /*
>    * Convert user-nice values [ -20 ... 0 ... 19 ]
>    * to static priority [ MAX_RT_PRIO..MAX_PRIO-1 ],
> @@ -646,7 +648,9 @@ static inline void sched_info_switch(tas
>   #define sched_info_switch(t, next)	do { } while (0)
>   #endif /* CONFIG_SCHEDSTATS */
>
> +#ifdef CONFIG_SMP
>   static __cacheline_aligned_in_smp atomic_t rt_overload;
> +#endif
>
>   static inline void inc_rt_tasks(task_t *p, runqueue_t *rq)
>   {
> @@ -1473,10 +1477,11 @@ static inline int wake_idle(int cpu, tas
>   static int try_to_wake_up(task_t *p, unsigned int state, int sync, int mutex)
>   {
>   	int cpu, this_cpu, success = 0;
> -	runqueue_t *this_rq, *rq;
> +	runqueue_t *rq;
>   	unsigned long flags;
>   	long old_state;
>   #ifdef CONFIG_SMP
> +	runqueue_t *this_rq;
>   	unsigned long load, this_load;
>   	struct sched_domain *sd, *this_sd = NULL;
>   	int new_cpu;
> @@ -4351,6 +4356,18 @@ int setscheduler(struct task_struct *p,
>   			resched_task(rq->curr);
>   	}
>   	task_rq_unlock(rq, &flags);
> +
> +	/*
> +	 * If the process is blocked on rt-mutex, it will now wake up and
> +	 * reinsert itself into the wait list and boost the owner correctly
> +	 */
> +	if (p->pi_blocked_on) {
> +		if (p->pi_blocked_on->save_state)
> +			wake_up_process_mutex(p);
> +		else
> +			wake_up_process(p);
> +	}
> +
>   	spin_unlock_irqrestore(&p->pi_lock, fp);
>   	return 0;
>   }
> @@ -7086,4 +7103,3 @@ void notrace preempt_enable_no_resched(v
>
>   EXPORT_SYMBOL(preempt_enable_no_resched);
>   #endif
> -
> Index: linux-2.6.17-rt1/kernel/rtmutex_common.h
> ===================================================================
> --- linux-2.6.17-rt1.orig/kernel/rtmutex_common.h
> +++ linux-2.6.17-rt1/kernel/rtmutex_common.h
> @@ -49,6 +49,7 @@ struct rt_mutex_waiter {
>   	struct plist_node	pi_list_entry;
>   	struct task_struct	*task;
>   	struct rt_mutex		*lock;
> +	int                     save_state;
>   #ifdef CONFIG_DEBUG_RT_MUTEXES
>   	unsigned long		ip;
>   	pid_t			deadlock_task_pid;
>
-
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