diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/rcu/rcu.h | 2 | ||||
| -rw-r--r-- | kernel/rcu/tasks.h | 32 | ||||
| -rw-r--r-- | kernel/rcu/tree.c | 43 |
3 files changed, 63 insertions, 14 deletions
diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h index 0d866eaa4cc8..b531c33e9545 100644 --- a/kernel/rcu/rcu.h +++ b/kernel/rcu/rcu.h @@ -500,6 +500,7 @@ static inline void rcu_expedite_gp(void) { } static inline void rcu_unexpedite_gp(void) { } static inline void rcu_async_hurry(void) { } static inline void rcu_async_relax(void) { } +static inline bool rcu_cpu_online(int cpu) { return true; } #else /* #ifdef CONFIG_TINY_RCU */ bool rcu_gp_is_normal(void); /* Internal RCU use. */ bool rcu_gp_is_expedited(void); /* Internal RCU use. */ @@ -509,6 +510,7 @@ void rcu_unexpedite_gp(void); void rcu_async_hurry(void); void rcu_async_relax(void); void rcupdate_announce_bootup_oddness(void); +bool rcu_cpu_online(int cpu); #ifdef CONFIG_TASKS_RCU_GENERIC void show_rcu_tasks_gp_kthreads(void); #else /* #ifdef CONFIG_TASKS_RCU_GENERIC */ diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index 1fa631168594..f54d5782eca0 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -895,10 +895,36 @@ static void rcu_tasks_pregp_step(struct list_head *hop) synchronize_rcu(); } +/* Check for quiescent states since the pregp's synchronize_rcu() */ +static bool rcu_tasks_is_holdout(struct task_struct *t) +{ + int cpu; + + /* Has the task been seen voluntarily sleeping? */ + if (!READ_ONCE(t->on_rq)) + return false; + + /* + * Idle tasks (or idle injection) within the idle loop are RCU-tasks + * quiescent states. But CPU boot code performed by the idle task + * isn't a quiescent state. + */ + if (is_idle_task(t)) + return false; + + cpu = task_cpu(t); + + /* Idle tasks on offline CPUs are RCU-tasks quiescent states. */ + if (t == idle_task(cpu) && !rcu_cpu_online(cpu)) + return false; + + return true; +} + /* Per-task initial processing. */ static void rcu_tasks_pertask(struct task_struct *t, struct list_head *hop) { - if (t != current && READ_ONCE(t->on_rq) && !is_idle_task(t)) { + if (t != current && rcu_tasks_is_holdout(t)) { get_task_struct(t); t->rcu_tasks_nvcsw = READ_ONCE(t->nvcsw); WRITE_ONCE(t->rcu_tasks_holdout, true); @@ -947,7 +973,7 @@ static void check_holdout_task(struct task_struct *t, if (!READ_ONCE(t->rcu_tasks_holdout) || t->rcu_tasks_nvcsw != READ_ONCE(t->nvcsw) || - !READ_ONCE(t->on_rq) || + !rcu_tasks_is_holdout(t) || (IS_ENABLED(CONFIG_NO_HZ_FULL) && !is_idle_task(t) && t->rcu_tasks_idle_cpu >= 0)) { WRITE_ONCE(t->rcu_tasks_holdout, false); @@ -1525,7 +1551,7 @@ static int trc_inspect_reader(struct task_struct *t, void *bhp_in) } else { // The task is not running, so C-language access is safe. nesting = t->trc_reader_nesting; - WARN_ON_ONCE(ofl && task_curr(t) && !is_idle_task(t)); + WARN_ON_ONCE(ofl && task_curr(t) && (t != idle_task(task_cpu(t)))); if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB) && ofl) n_heavy_reader_ofl_updates++; } diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index d3a97e129020..3ac3c846105f 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -755,14 +755,19 @@ static int dyntick_save_progress_counter(struct rcu_data *rdp) } /* - * Return true if the specified CPU has passed through a quiescent - * state by virtue of being in or having passed through an dynticks - * idle state since the last call to dyntick_save_progress_counter() - * for this same CPU, or by virtue of having been offline. + * Returns positive if the specified CPU has passed through a quiescent state + * by virtue of being in or having passed through an dynticks idle state since + * the last call to dyntick_save_progress_counter() for this same CPU, or by + * virtue of having been offline. + * + * Returns negative if the specified CPU needs a force resched. + * + * Returns zero otherwise. */ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) { unsigned long jtsq; + int ret = 0; struct rcu_node *rnp = rdp->mynode; /* @@ -848,8 +853,8 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) (time_after(jiffies, READ_ONCE(rdp->last_fqs_resched) + jtsq * 3) || rcu_state.cbovld)) { WRITE_ONCE(rdp->rcu_urgent_qs, true); - resched_cpu(rdp->cpu); WRITE_ONCE(rdp->last_fqs_resched, jiffies); + ret = -1; } /* @@ -862,8 +867,8 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) if (time_after(jiffies, rcu_state.jiffies_resched)) { if (time_after(jiffies, READ_ONCE(rdp->last_fqs_resched) + jtsq)) { - resched_cpu(rdp->cpu); WRITE_ONCE(rdp->last_fqs_resched, jiffies); + ret = -1; } if (IS_ENABLED(CONFIG_IRQ_WORK) && !rdp->rcu_iw_pending && rdp->rcu_iw_gp_seq != rnp->gp_seq && @@ -892,7 +897,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) } } - return 0; + return ret; } /* Trace-event wrapper function for trace_rcu_future_grace_period. */ @@ -2271,15 +2276,15 @@ static void force_qs_rnp(int (*f)(struct rcu_data *rdp)) { int cpu; unsigned long flags; - unsigned long mask; - struct rcu_data *rdp; struct rcu_node *rnp; rcu_state.cbovld = rcu_state.cbovldnext; rcu_state.cbovldnext = false; rcu_for_each_leaf_node(rnp) { + unsigned long mask = 0; + unsigned long rsmask = 0; + cond_resched_tasks_rcu_qs(); - mask = 0; raw_spin_lock_irqsave_rcu_node(rnp, flags); rcu_state.cbovldnext |= !!rnp->cbovldmask; if (rnp->qsmask == 0) { @@ -2297,11 +2302,17 @@ static void force_qs_rnp(int (*f)(struct rcu_data *rdp)) continue; } for_each_leaf_node_cpu_mask(rnp, cpu, rnp->qsmask) { + struct rcu_data *rdp; + int ret; + rdp = per_cpu_ptr(&rcu_data, cpu); - if (f(rdp)) { + ret = f(rdp); + if (ret > 0) { mask |= rdp->grpmask; rcu_disable_urgency_upon_qs(rdp); } + if (ret < 0) + rsmask |= rdp->grpmask; } if (mask != 0) { /* Idle/offline CPUs, report (releases rnp->lock). */ @@ -2310,6 +2321,9 @@ static void force_qs_rnp(int (*f)(struct rcu_data *rdp)) /* Nothing to do here, so just drop the lock. */ raw_spin_unlock_irqrestore_rcu_node(rnp, flags); } + + for_each_leaf_node_cpu_mask(rnp, cpu, rsmask) + resched_cpu(cpu); } } @@ -4195,6 +4209,13 @@ static bool rcu_rdp_cpu_online(struct rcu_data *rdp) return !!(rdp->grpmask & rcu_rnp_online_cpus(rdp->mynode)); } +bool rcu_cpu_online(int cpu) +{ + struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); + + return rcu_rdp_cpu_online(rdp); +} + #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) /* |