On 10/11, Peter Zijlstra wrote: > > As a penance I'll start by removing all get_online_cpus() usage from the > scheduler.
I only looked at the change in setaffinity, > @@ -3706,7 +3707,6 @@ long sched_setaffinity(pid_t pid, const struct cpumask > *in_mask) > struct task_struct *p; > int retval; > > - get_online_cpus(); > rcu_read_lock(); Hmm. In theory task_rq_lock() doesn't imply rcu-lock, so set_cpus_allowed_ptr() can miss the change in cpu_active_mask. But this is probably fine, CPU_DYING does __migrate_task(). However. This means that sched_setaffinity() can fail if it races with the failing cpu_down() (say, __cpu_notify(CPU_DOWN_PREPARE) fails). Probably we do not really care, just this looks a bit confusing. > @@ -3814,7 +3813,6 @@ long sched_getaffinity(pid_t pid, struct cpumask *mask) > unsigned long flags; > int retval; > > - get_online_cpus(); This change is probably fine in any case? > rcu_read_lock(); > > retval = -ESRCH; > @@ -3827,12 +3825,11 @@ long sched_getaffinity(pid_t pid, struct cpumask > *mask) > goto out_unlock; > > raw_spin_lock_irqsave(&p->pi_lock, flags); > - cpumask_and(mask, &p->cpus_allowed, cpu_online_mask); > + cpumask_and(mask, &p->cpus_allowed, cpu_active_mask); But I am just curious, is this change is strictly needed? Afaics we do not care if we race with set_cpu_online(true/false). Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
