diff options
| -rw-r--r-- | kernel/sched_cpupri.c | 62 | ||||
| -rw-r--r-- | kernel/sched_cpupri.h | 5 |
2 files changed, 41 insertions, 26 deletions
diff --git a/kernel/sched_cpupri.c b/kernel/sched_cpupri.c index 2722dc1..7761a266 100644 --- a/kernel/sched_cpupri.c +++ b/kernel/sched_cpupri.c @@ -47,9 +47,6 @@ static int convert_prio(int prio) return cpupri; } -#define for_each_cpupri_active(array, idx) \ - for_each_set_bit(idx, array, CPUPRI_NR_PRIORITIES) - /** * cpupri_find - find the best (lowest-pri) CPU in the system * @cp: The cpupri context @@ -71,11 +68,33 @@ int cpupri_find(struct cpupri *cp, struct task_struct *p, int idx = 0; int task_pri = convert_prio(p->prio); - for_each_cpupri_active(cp->pri_active, idx) { + if (task_pri >= MAX_RT_PRIO) + return 0; + + for (idx = 0; idx < task_pri; idx++) { struct cpupri_vec *vec = &cp->pri_to_cpu[idx]; - if (idx >= task_pri) - break; + if (!atomic_read(&(vec)->count)) + continue; + /* + * When looking at the vector, we need to read the counter, + * do a memory barrier, then read the mask. + * + * Note: This is still all racey, but we can deal with it. + * Ideally, we only want to look at masks that are set. + * + * If a mask is not set, then the only thing wrong is that we + * did a little more work than necessary. + * + * If we read a zero count but the mask is set, because of the + * memory barriers, that can only happen when the highest prio + * task for a run queue has left the run queue, in which case, + * it will be followed by a pull. If the task we are processing + * fails to find a proper place to go, that pull request will + * pull this task if the run queue is running at a lower + * priority. + */ + smp_rmb(); if (cpumask_any_and(&p->cpus_allowed, vec->mask) >= nr_cpu_ids) continue; @@ -115,7 +134,6 @@ void cpupri_set(struct cpupri *cp, int cpu, int newpri) { int *currpri = &cp->cpu_to_pri[cpu]; int oldpri = *currpri; - unsigned long flags; newpri = convert_prio(newpri); @@ -134,26 +152,25 @@ void cpupri_set(struct cpupri *cp, int cpu, int newpri) if (likely(newpri != CPUPRI_INVALID)) { struct cpupri_vec *vec = &cp->pri_to_cpu[newpri]; - raw_spin_lock_irqsave(&vec->lock, flags); - cpumask_set_cpu(cpu, vec->mask); - vec->count++; - if (vec->count == 1) - set_bit(newpri, cp->pri_active); - - raw_spin_unlock_irqrestore(&vec->lock, flags); + /* + * When adding a new vector, we update the mask first, + * do a write memory barrier, and then update the count, to + * make sure the vector is visible when count is set. + */ + smp_wmb(); + atomic_inc(&(vec)->count); } if (likely(oldpri != CPUPRI_INVALID)) { struct cpupri_vec *vec = &cp->pri_to_cpu[oldpri]; - raw_spin_lock_irqsave(&vec->lock, flags); - - vec->count--; - if (!vec->count) - clear_bit(oldpri, cp->pri_active); + /* + * When removing from the vector, we decrement the counter first + * do a memory barrier and then clear the mask. + */ + atomic_dec(&(vec)->count); + smp_wmb(); cpumask_clear_cpu(cpu, vec->mask); - - raw_spin_unlock_irqrestore(&vec->lock, flags); } *currpri = newpri; @@ -175,8 +192,7 @@ int cpupri_init(struct cpupri *cp) for (i = 0; i < CPUPRI_NR_PRIORITIES; i++) { struct cpupri_vec *vec = &cp->pri_to_cpu[i]; - raw_spin_lock_init(&vec->lock); - vec->count = 0; + atomic_set(&vec->count, 0); if (!zalloc_cpumask_var(&vec->mask, GFP_KERNEL)) goto cleanup; } diff --git a/kernel/sched_cpupri.h b/kernel/sched_cpupri.h index 9fc7d38..6b4cd17 100644 --- a/kernel/sched_cpupri.h +++ b/kernel/sched_cpupri.h @@ -12,9 +12,8 @@ /* values 2-101 are RT priorities 0-99 */ struct cpupri_vec { - raw_spinlock_t lock; - int count; - cpumask_var_t mask; + atomic_t count; + cpumask_var_t mask; }; struct cpupri { |
