sched/membarrier: fix missing local execution of ipi_sync_rq_state()

The function sync_runqueues_membarrier_state() should copy the
membarrier state from the @mm received as parameter to each runqueue
currently running tasks using that mm.

However, the use of smp_call_function_many() skips the current runqueue,
which is unintended. Replace by a call to on_each_cpu_mask().

Fixes: 227a4aad ("sched/membarrier: Fix p->mm->membarrier_state racy load")
Reported-by: Nadav Amit <nadav.amit@gmail.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: stable@vger.kernel.org # 5.4.x+
Link: https://lore.kernel.org/r/74F1E842-4A84-47BF-B6C2-5407DFDD4A4A@gmail.com

kernel/sched/membarrier.c

@@ -471,9 +471,7 @@ static int sync_runqueues_membarrier_state(struct mm_struct *mm)
 	}
 	rcu_read_unlock();
 
-	preempt_disable();
-	smp_call_function_many(tmpmask, ipi_sync_rq_state, mm, 1);
-	preempt_enable();
+	on_each_cpu_mask(tmpmask, ipi_sync_rq_state, mm, true);
 
 	free_cpumask_var(tmpmask);
 	cpus_read_unlock();