diff options
| -rw-r--r-- | kernel/rcutree.c | 250 |
1 files changed, 135 insertions, 115 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c index ddc6acc85d26..f0c0c1b4b6d4 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -1028,95 +1028,159 @@ rcu_start_gp_per_cpu(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_dat } /* - * Body of kthread that handles grace periods. + * Initialize a new grace period. */ -static int __noreturn rcu_gp_kthread(void *arg) +static int rcu_gp_init(struct rcu_state *rsp) { - unsigned long gp_duration; struct rcu_data *rdp; - struct rcu_node *rnp; - struct rcu_state *rsp = arg; + struct rcu_node *rnp = rcu_get_root(rsp); - for (;;) { + raw_spin_lock_irq(&rnp->lock); + rsp->gp_flags = 0; - /* Handle grace-period start. */ - rnp = rcu_get_root(rsp); - for (;;) { - wait_event_interruptible(rsp->gp_wq, rsp->gp_flags); - if (rsp->gp_flags) - break; - flush_signals(current); - } + if (rcu_gp_in_progress(rsp)) { + /* Grace period already in progress, don't start another. */ + raw_spin_unlock_irq(&rnp->lock); + return 0; + } + + if (rsp->fqs_active) { + /* + * We need a grace period, but force_quiescent_state() + * is running. Tell it to start one on our behalf. + */ + rsp->fqs_need_gp = 1; + raw_spin_unlock_irq(&rnp->lock); + return 0; + } + + /* Advance to a new grace period and initialize state. */ + rsp->gpnum++; + trace_rcu_grace_period(rsp->name, rsp->gpnum, "start"); + WARN_ON_ONCE(rsp->fqs_state == RCU_GP_INIT); + rsp->fqs_state = RCU_GP_INIT; /* Stop force_quiescent_state. */ + rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; + record_gp_stall_check_time(rsp); + raw_spin_unlock_irq(&rnp->lock); + + /* Exclude any concurrent CPU-hotplug operations. */ + get_online_cpus(); + + /* + * Set the quiescent-state-needed bits in all the rcu_node + * structures for all currently online CPUs in breadth-first order, + * starting from the root rcu_node structure, relying on the layout + * of the tree within the rsp->node[] array. Note that other CPUs + * will access only the leaves of the hierarchy, thus seeing that no + * grace period is in progress, at least until the corresponding + * leaf node has been initialized. In addition, we have excluded + * CPU-hotplug operations. + * + * The grace period cannot complete until the initialization + * process finishes, because this kthread handles both. + */ + rcu_for_each_node_breadth_first(rsp, rnp) { raw_spin_lock_irq(&rnp->lock); - rsp->gp_flags = 0; rdp = this_cpu_ptr(rsp->rda); + rcu_preempt_check_blocked_tasks(rnp); + rnp->qsmask = rnp->qsmaskinit; + rnp->gpnum = rsp->gpnum; + rnp->completed = rsp->completed; + if (rnp == rdp->mynode) + rcu_start_gp_per_cpu(rsp, rnp, rdp); + rcu_preempt_boost_start_gp(rnp); + trace_rcu_grace_period_init(rsp->name, rnp->gpnum, + rnp->level, rnp->grplo, + rnp->grphi, rnp->qsmask); + raw_spin_unlock_irq(&rnp->lock); + cond_resched(); + } - if (rcu_gp_in_progress(rsp)) { - /* - * A grace period is already in progress, so - * don't start another one. - */ - raw_spin_unlock_irq(&rnp->lock); - cond_resched(); - continue; - } + rnp = rcu_get_root(rsp); + raw_spin_lock_irq(&rnp->lock); + /* force_quiescent_state() now OK. */ + rsp->fqs_state = RCU_SIGNAL_INIT; + raw_spin_unlock_irq(&rnp->lock); + put_online_cpus(); + return 1; +} - if (rsp->fqs_active) { - /* - * We need a grace period, but force_quiescent_state() - * is running. Tell it to start one on our behalf. - */ - rsp->fqs_need_gp = 1; - raw_spin_unlock_irq(&rnp->lock); - cond_resched(); - continue; - } +/* + * Clean up after the old grace period. + */ +static int rcu_gp_cleanup(struct rcu_state *rsp) +{ + unsigned long gp_duration; + struct rcu_data *rdp; + struct rcu_node *rnp = rcu_get_root(rsp); - /* Advance to a new grace period and initialize state. */ - rsp->gpnum++; - trace_rcu_grace_period(rsp->name, rsp->gpnum, "start"); - WARN_ON_ONCE(rsp->fqs_state == RCU_GP_INIT); - rsp->fqs_state = RCU_GP_INIT; /* Stop force_quiescent_state. */ - rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; - record_gp_stall_check_time(rsp); - raw_spin_unlock_irq(&rnp->lock); + raw_spin_lock_irq(&rnp->lock); + gp_duration = jiffies - rsp->gp_start; + if (gp_duration > rsp->gp_max) + rsp->gp_max = gp_duration; - /* Exclude any concurrent CPU-hotplug operations. */ - get_online_cpus(); + /* + * We know the grace period is complete, but to everyone else + * it appears to still be ongoing. But it is also the case + * that to everyone else it looks like there is nothing that + * they can do to advance the grace period. It is therefore + * safe for us to drop the lock in order to mark the grace + * period as completed in all of the rcu_node structures. + * + * But if this CPU needs another grace period, it will take + * care of this while initializing the next grace period. + * We use RCU_WAIT_TAIL instead of the usual RCU_DONE_TAIL + * because the callbacks have not yet been advanced: Those + * callbacks are waiting on the grace period that just now + * completed. + */ + rdp = this_cpu_ptr(rsp->rda); + if (*rdp->nxttail[RCU_WAIT_TAIL] == NULL) { + raw_spin_unlock_irq(&rnp->lock); /* - * Set the quiescent-state-needed bits in all the rcu_node - * structures for all currently online CPUs in breadth-first - * order, starting from the root rcu_node structure. - * This operation relies on the layout of the hierarchy - * within the rsp->node[] array. Note that other CPUs will - * access only the leaves of the hierarchy, which still - * indicate that no grace period is in progress, at least - * until the corresponding leaf node has been initialized. - * In addition, we have excluded CPU-hotplug operations. + * Propagate new ->completed value to rcu_node + * structures so that other CPUs don't have to + * wait until the start of the next grace period + * to process their callbacks. */ rcu_for_each_node_breadth_first(rsp, rnp) { raw_spin_lock_irq(&rnp->lock); - rcu_preempt_check_blocked_tasks(rnp); - rnp->qsmask = rnp->qsmaskinit; - rnp->gpnum = rsp->gpnum; - rnp->completed = rsp->completed; - if (rnp == rdp->mynode) - rcu_start_gp_per_cpu(rsp, rnp, rdp); - rcu_preempt_boost_start_gp(rnp); - trace_rcu_grace_period_init(rsp->name, rnp->gpnum, - rnp->level, rnp->grplo, - rnp->grphi, rnp->qsmask); + rnp->completed = rsp->gpnum; raw_spin_unlock_irq(&rnp->lock); cond_resched(); } - rnp = rcu_get_root(rsp); raw_spin_lock_irq(&rnp->lock); - /* force_quiescent_state() now OK. */ - rsp->fqs_state = RCU_SIGNAL_INIT; - raw_spin_unlock_irq(&rnp->lock); - put_online_cpus(); + } + + rsp->completed = rsp->gpnum; /* Declare grace period done. */ + trace_rcu_grace_period(rsp->name, rsp->completed, "end"); + rsp->fqs_state = RCU_GP_IDLE; + if (cpu_needs_another_gp(rsp, rdp)) + rsp->gp_flags = 1; + raw_spin_unlock_irq(&rnp->lock); + return 1; +} + +/* + * Body of kthread that handles grace periods. + */ +static int __noreturn rcu_gp_kthread(void *arg) +{ + struct rcu_state *rsp = arg; + struct rcu_node *rnp = rcu_get_root(rsp); + + for (;;) { + + /* Handle grace-period start. */ + for (;;) { + wait_event_interruptible(rsp->gp_wq, rsp->gp_flags); + if (rsp->gp_flags && rcu_gp_init(rsp)) + break; + cond_resched(); + flush_signals(current); + } /* Handle grace-period end. */ rnp = rcu_get_root(rsp); @@ -1125,56 +1189,12 @@ static int __noreturn rcu_gp_kthread(void *arg) !ACCESS_ONCE(rnp->qsmask) && !rcu_preempt_blocked_readers_cgp(rnp)); if (!ACCESS_ONCE(rnp->qsmask) && - !rcu_preempt_blocked_readers_cgp(rnp)) + !rcu_preempt_blocked_readers_cgp(rnp) && + rcu_gp_cleanup(rsp)) break; + cond_resched(); flush_signals(current); } - - raw_spin_lock_irq(&rnp->lock); - gp_duration = jiffies - rsp->gp_start; - if (gp_duration > rsp->gp_max) - rsp->gp_max = gp_duration; - - /* - * We know the grace period is complete, but to everyone else - * it appears to still be ongoing. But it is also the case - * that to everyone else it looks like there is nothing that - * they can do to advance the grace period. It is therefore - * safe for us to drop the lock in order to mark the grace - * period as completed in all of the rcu_node structures. - * - * But if this CPU needs another grace period, it will take - * care of this while initializing the next grace period. - * We use RCU_WAIT_TAIL instead of the usual RCU_DONE_TAIL - * because the callbacks have not yet been advanced: Those - * callbacks are waiting on the grace period that just now - * completed. - */ - if (*rdp->nxttail[RCU_WAIT_TAIL] == NULL) { - raw_spin_unlock_irq(&rnp->lock); - - /* - * Propagate new ->completed value to rcu_node - * structures so that other CPUs don't have to - * wait until the start of the next grace period - * to process their callbacks. - */ - rcu_for_each_node_breadth_first(rsp, rnp) { - raw_spin_lock_irq(&rnp->lock); - rnp->completed = rsp->gpnum; - raw_spin_unlock_irq(&rnp->lock); - cond_resched(); - } - rnp = rcu_get_root(rsp); - raw_spin_lock_irq(&rnp->lock); - } - - rsp->completed = rsp->gpnum; /* Declare grace period done. */ - trace_rcu_grace_period(rsp->name, rsp->completed, "end"); - rsp->fqs_state = RCU_GP_IDLE; - if (cpu_needs_another_gp(rsp, rdp)) - rsp->gp_flags = 1; - raw_spin_unlock_irq(&rnp->lock); } } |