diff options
Diffstat (limited to 'kernel/rcuclassic.c')
| -rw-r--r-- | kernel/rcuclassic.c | 52 |
1 files changed, 49 insertions, 3 deletions
diff --git a/kernel/rcuclassic.c b/kernel/rcuclassic.c index f4ffbd0f306..16eeeaa9d61 100644 --- a/kernel/rcuclassic.c +++ b/kernel/rcuclassic.c @@ -89,8 +89,22 @@ 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) 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(); } @@ -529,7 +575,7 @@ static void __cpuinit rcu_online_cpu(int cpu) rcu_init_percpu_data(cpu, &rcu_ctrlblk, rdp); rcu_init_percpu_data(cpu, &rcu_bh_ctrlblk, bh_rdp); - open_softirq(RCU_SOFTIRQ, rcu_process_callbacks, NULL); + open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); } static int __cpuinit rcu_cpu_notify(struct notifier_block *self, |