SMP: Fix a error introduced in 36b676eea6 and fully decouple disabling of pre-emption from critical sections.

sched/irq/irq_csection.c

@@ -507,36 +507,6 @@ void leave_critical_section(irqstate_t flags)
               rtcb->irqcount = 0;
               spin_clrbit(&g_cpu_irqset, cpu, &g_cpu_irqsetlock,
                           &g_cpu_irqlock);
-
-              /* Have all CPUs released the lock? */
-
-              if (!spin_islocked(&g_cpu_irqlock))
-                {
-                  /* Check if there are pending tasks and that pre-emption
-                   * is also enabled.
-                   *
-                   * REVISIT: Is there an issue here?  up_release_pending()
-                   * must be called from within a critical section but here
-                   * we have just left the critical section.  At least we
-                   * still have interrupts disabled on this CPU.
-                   */
-
-                  if (g_pendingtasks.head != NULL &&
-                      !spin_islocked(&g_cpu_schedlock))
-                    {
-                      /* Release any ready-to-run tasks that have collected
-                       * in g_pendingtasks if the scheduler is not locked.
-                       *
-                       * NOTE: This operation has a very high likelihood of
-                       * causing this task to be switched out!
-                       *
-                       * REVISIT: Should this not be done while we are in the
-                       * critical section.
-                       */
-
-                      up_release_pending();
-                    }
-                }
             }
         }
     }