Use generic preemption function in GSN- and PSN-EDF.

This patch updates non-preemptive section support in
GSN- and PSN-EDF.

2 files changed, 30 insertions, 46 deletions

diff --git a/litmus/sched_gsn_edf.c b/litmus/sched_gsn_edf.c
index 2a0ee50d26a2..b9310dd6f75c 100644
--- a/litmus/sched_gsn_edf.c
+++ b/litmus/sched_gsn_edf.c
@@ -242,27 +242,9 @@ static noinline void unlink(struct task_struct* t)
 
 /* preempt - force a CPU to reschedule
  */
-static noinline void preempt(cpu_entry_t *entry)
+static void preempt(cpu_entry_t *entry)
 {
-        /* We cannot make the is_np() decision here if it is a remote CPU
-         * because requesting exit_np() requires that we currently use the
-         * address space of the task. Thus, in the remote case we just send
-         * the IPI and let schedule() handle the problem.
-         */
-
-        if (smp_processor_id() == entry->cpu) {
-                if (entry->scheduled && is_np(entry->scheduled))
-                        request_exit_np(entry->scheduled);
-                else
-                        set_tsk_need_resched(current);
-        } else
-                /* in case that it is a remote CPU we have to defer the
-                 * the decision to the remote CPU
-                 * FIXME: We could save a few IPI's here if we leave the flag
-                 * set when we are waiting for a np_exit().
-                 */
-                if (!test_will_schedule(entry->cpu))
-                        smp_send_reschedule(entry->cpu);
+        preempt_if_preemptable(entry->scheduled, entry->cpu);
 }
 
 /* requeue - Put an unlinked task into gsn-edf domain.
@@ -364,7 +346,7 @@ static void gsnedf_tick(struct task_struct* t)
                         TRACE("gsnedf_scheduler_tick: "
                               "%d is preemptable "
                               " => FORCE_RESCHED\n", t->pid);
-                } else {
+                } else if (is_user_np(t)) {
                         TRACE("gsnedf_scheduler_tick: "
                               "%d is non-preemptable, "
                               "preemption delayed.\n", t->pid);
diff --git a/litmus/sched_psn_edf.c b/litmus/sched_psn_edf.c
index f0ab8ebc5111..3a93124e24f6 100644
--- a/litmus/sched_psn_edf.c
+++ b/litmus/sched_psn_edf.c
@@ -68,16 +68,7 @@ static void requeue(struct task_struct* t, rt_domain_t *edf)
 /* we assume the lock is being held */
 static void preempt(psnedf_domain_t *pedf)
 {
-        if (smp_processor_id() == pedf->cpu) {
-                if (pedf->scheduled && is_np(pedf->scheduled))
-                        request_exit_np(pedf->scheduled);
-                else
-                        set_tsk_need_resched(current);
-        } else
-                /* in case that it is a remote CPU we have to defer the
-                 * the decision to the remote CPU
-                 */
-                smp_send_reschedule(pedf->cpu);
+        preempt_if_preemptable(pedf->scheduled, pedf->cpu);
 }
 
 /* This check is trivial in partioned systems as we only have to consider
@@ -86,16 +77,15 @@ static void preempt(psnedf_domain_t *pedf)
 static int psnedf_check_resched(rt_domain_t *edf)
 {
         psnedf_domain_t *pedf = container_of(edf, psnedf_domain_t, domain);
-        int ret = 0;
 
         /* because this is a callback from rt_domain_t we already hold
          * the necessary lock for the ready queue
          */
         if (edf_preemption_needed(edf, pedf->scheduled)) {
                 preempt(pedf);
-                ret = 1;
-        }
-        return ret;
+                return 1;
+        } else
+                return 0;
 }
 
 static void job_completion(struct task_struct* t)
@@ -121,7 +111,7 @@ static void psnedf_tick(struct task_struct *t)
                         TRACE("psnedf_scheduler_tick: "
                               "%d is preemptable "
                               " => FORCE_RESCHED\n", t->pid);
-                } else {
+                } else if (is_user_np(t)) {
                         TRACE("psnedf_scheduler_tick: "
                               "%d is non-preemptable, "
                               "preemption delayed.\n", t->pid);
@@ -394,6 +384,7 @@ static long psnedf_return_priority(struct pi_semaphore *sem)
         rt_domain_t*            edf  = task_edf(t);
         int                     ret  = 0;
         int                     cpu  = get_partition(current);
+        int still_np;
 
 
         /* Find new highest-priority semaphore task
@@ -404,23 +395,34 @@ static long psnedf_return_priority(struct pi_semaphore *sem)
         if (t == sem->hp.cpu_task[cpu])
                 edf_set_hp_cpu_task(sem, cpu);
 
-        take_np(t);
+        still_np = take_np(current);
+
+        /* Since we don't nest resources, this
+         * should always be zero */
+        BUG_ON(still_np);
+
         if (current->rt_param.inh_task) {
                 TRACE_CUR("return priority of %s/%d\n",
                           current->rt_param.inh_task->comm,
                           current->rt_param.inh_task->pid);
-                spin_lock(&pedf->slock);
+        } else
+                TRACE_CUR(" no priority to return %p\n", sem);
 
-                /* Reset inh_task to NULL. */
-                current->rt_param.inh_task = NULL;
 
-                /* check if we need to reschedule */
-                if (edf_preemption_needed(edf, current))
-                        preempt(pedf);
+        /* Always check for delayed preemptions that might have become
+         * necessary due to non-preemptive execution.
+         */
+        spin_lock(&pedf->slock);
+
+        /* Reset inh_task to NULL. */
+        current->rt_param.inh_task = NULL;
+
+        /* check if we need to reschedule */
+        if (edf_preemption_needed(edf, current))
+                preempt(pedf);
+
+        spin_unlock(&pedf->slock);
 
-                spin_unlock(&pedf->slock);
-        } else
-                TRACE_CUR(" no priority to return %p\n", sem);
 
         return ret;
 }