Merge branch 'linus' into cpus4096

[pandora-kernel.git] / kernel / rcuclassic.c

diff --git a/kernel/rcuclassic.c b/kernel/rcuclassic.c
index f6e01f3..6f8696c 100644 (file)
--- a/kernel/rcuclassic.c
+++ b/kernel/rcuclassic.c
@@ -89,10 +89,24 @@ static void force_quiescent_state(struct rcu_data *rdp,
                /*
                 * Don't send IPI to itself. With irqs disabled,
                 * rdp->cpu is the current cpu.
+                *
+                * cpu_online_map is updated by the _cpu_down()
+                * using stop_machine_run(). Since we're in irqs disabled
+                * section, stop_machine_run() is not exectuting, hence
+                * the cpu_online_map is stable.
+                *
+                * However,  a cpu might have been offlined _just_ before
+                * we disabled irqs while entering here.
+                * And rcu subsystem might not yet have handled the CPU_DEAD
+                * notification, leading to the offlined cpu's bit
+                * being set in the rcp->cpumask.
+                *
+                * Hence cpumask = (rcp->cpumask & cpu_online_map) to prevent
+                * sending smp_reschedule() to an offlined CPU.
                 */
-               cpumask = rcp->cpumask;
+               cpus_and(cpumask, rcp->cpumask, cpu_online_map);
                cpu_clear(rdp->cpu, cpumask);
-               for_each_cpu_mask(cpu, cpumask)
+               for_each_cpu_mask_nr(cpu, cpumask)
                        smp_send_reschedule(cpu);
        }
 }
@@ -373,6 +387,10 @@ static void __rcu_offline_cpu(struct rcu_data *this_rdp,
        rcu_move_batch(this_rdp, rdp->donelist, rdp->donetail);
        rcu_move_batch(this_rdp, rdp->curlist, rdp->curtail);
        rcu_move_batch(this_rdp, rdp->nxtlist, rdp->nxttail);
+
+       local_irq_disable();
+       this_rdp->qlen += rdp->qlen;
+       local_irq_enable();
 }
 
 static void rcu_offline_cpu(int cpu)
@@ -502,10 +520,38 @@ void rcu_check_callbacks(int cpu, int user)
        if (user ||
            (idle_cpu(cpu) && !in_softirq() &&
                                hardirq_count() <= (1 << HARDIRQ_SHIFT))) {
+
+               /*
+                * Get here if this CPU took its interrupt from user
+                * mode or from the idle loop, and if this is not a
+                * nested interrupt.  In this case, the CPU is in
+                * a quiescent state, so count it.
+                *
+                * Also do a memory barrier.  This is needed to handle
+                * the case where writes from a preempt-disable section
+                * of code get reordered into schedule() by this CPU's
+                * write buffer.  The memory barrier makes sure that
+                * the rcu_qsctr_inc() and rcu_bh_qsctr_inc() are see
+                * by other CPUs to happen after any such write.
+                */
+
+               smp_mb();  /* See above block comment. */
                rcu_qsctr_inc(cpu);
                rcu_bh_qsctr_inc(cpu);
-       } else if (!in_softirq())
+
+       } else if (!in_softirq()) {
+
+               /*
+                * Get here if this CPU did not take its interrupt from
+                * softirq, in other words, if it is not interrupting
+                * a rcu_bh read-side critical section.  This is an _bh
+                * critical section, so count it.  The memory barrier
+                * is needed for the same reason as is the above one.
+                */
+
+               smp_mb();  /* See above block comment. */
                rcu_bh_qsctr_inc(cpu);
+       }
        raise_rcu_softirq();
 }