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

[Esben Nielsen <nielsen.esben@googlemail.com>]

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On Wed, 21 Jun 2006, Steven Rostedt wrote:

>
> 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?
>

Does it help if I send it as an attachment?

Esben


> 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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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;