| /* |
| * Read-Copy Update mechanism for mutual exclusion |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License as published by |
| * the Free Software Foundation; either version 2 of the License, or |
| * (at your option) any later version. |
| * |
| * This program is distributed in the hope that it will be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| * GNU General Public License for more details. |
| * |
| * You should have received a copy of the GNU General Public License |
| * along with this program; if not, write to the Free Software |
| * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
| * |
| * Copyright IBM Corporation, 2008 |
| * |
| * Authors: Dipankar Sarma <dipankar@in.ibm.com> |
| * Manfred Spraul <manfred@colorfullife.com> |
| * Paul E. McKenney <paulmck@linux.vnet.ibm.com> Hierarchical version |
| * |
| * Based on the original work by Paul McKenney <paulmck@us.ibm.com> |
| * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. |
| * |
| * For detailed explanation of Read-Copy Update mechanism see - |
| * Documentation/RCU |
| */ |
| #include <linux/types.h> |
| #include <linux/kernel.h> |
| #include <linux/init.h> |
| #include <linux/spinlock.h> |
| #include <linux/smp.h> |
| #include <linux/rcupdate.h> |
| #include <linux/interrupt.h> |
| #include <linux/sched.h> |
| #include <linux/nmi.h> |
| #include <asm/atomic.h> |
| #include <linux/bitops.h> |
| #include <linux/module.h> |
| #include <linux/completion.h> |
| #include <linux/moduleparam.h> |
| #include <linux/percpu.h> |
| #include <linux/notifier.h> |
| #include <linux/cpu.h> |
| #include <linux/mutex.h> |
| #include <linux/time.h> |
| |
| #include "rcutree.h" |
| |
| /* Data structures. */ |
| |
| #define RCU_STATE_INITIALIZER(name) { \ |
| .level = { &name.node[0] }, \ |
| .levelcnt = { \ |
| NUM_RCU_LVL_0, /* root of hierarchy. */ \ |
| NUM_RCU_LVL_1, \ |
| NUM_RCU_LVL_2, \ |
| NUM_RCU_LVL_3, /* == MAX_RCU_LVLS */ \ |
| }, \ |
| .signaled = RCU_GP_IDLE, \ |
| .gpnum = -300, \ |
| .completed = -300, \ |
| .onofflock = __SPIN_LOCK_UNLOCKED(&name.onofflock), \ |
| .orphan_cbs_list = NULL, \ |
| .orphan_cbs_tail = &name.orphan_cbs_list, \ |
| .orphan_qlen = 0, \ |
| .fqslock = __SPIN_LOCK_UNLOCKED(&name.fqslock), \ |
| .n_force_qs = 0, \ |
| .n_force_qs_ngp = 0, \ |
| } |
| |
| struct rcu_state rcu_sched_state = RCU_STATE_INITIALIZER(rcu_sched_state); |
| DEFINE_PER_CPU(struct rcu_data, rcu_sched_data); |
| |
| struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state); |
| DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); |
| |
| |
| /* |
| * Return true if an RCU grace period is in progress. The ACCESS_ONCE()s |
| * permit this function to be invoked without holding the root rcu_node |
| * structure's ->lock, but of course results can be subject to change. |
| */ |
| static int rcu_gp_in_progress(struct rcu_state *rsp) |
| { |
| return ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum); |
| } |
| |
| /* |
| * Note a quiescent state. Because we do not need to know |
| * how many quiescent states passed, just if there was at least |
| * one since the start of the grace period, this just sets a flag. |
| */ |
| void rcu_sched_qs(int cpu) |
| { |
| struct rcu_data *rdp; |
| |
| rdp = &per_cpu(rcu_sched_data, cpu); |
| rdp->passed_quiesc_completed = rdp->completed; |
| barrier(); |
| rdp->passed_quiesc = 1; |
| rcu_preempt_note_context_switch(cpu); |
| } |
| |
| void rcu_bh_qs(int cpu) |
| { |
| struct rcu_data *rdp; |
| |
| rdp = &per_cpu(rcu_bh_data, cpu); |
| rdp->passed_quiesc_completed = rdp->completed; |
| barrier(); |
| rdp->passed_quiesc = 1; |
| } |
| |
| #ifdef CONFIG_NO_HZ |
| DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { |
| .dynticks_nesting = 1, |
| .dynticks = 1, |
| }; |
| #endif /* #ifdef CONFIG_NO_HZ */ |
| |
| static int blimit = 10; /* Maximum callbacks per softirq. */ |
| static int qhimark = 10000; /* If this many pending, ignore blimit. */ |
| static int qlowmark = 100; /* Once only this many pending, use blimit. */ |
| |
| module_param(blimit, int, 0); |
| module_param(qhimark, int, 0); |
| module_param(qlowmark, int, 0); |
| |
| static void force_quiescent_state(struct rcu_state *rsp, int relaxed); |
| static int rcu_pending(int cpu); |
| |
| /* |
| * Return the number of RCU-sched batches processed thus far for debug & stats. |
| */ |
| long rcu_batches_completed_sched(void) |
| { |
| return rcu_sched_state.completed; |
| } |
| EXPORT_SYMBOL_GPL(rcu_batches_completed_sched); |
| |
| /* |
| * Return the number of RCU BH batches processed thus far for debug & stats. |
| */ |
| long rcu_batches_completed_bh(void) |
| { |
| return rcu_bh_state.completed; |
| } |
| EXPORT_SYMBOL_GPL(rcu_batches_completed_bh); |
| |
| /* |
| * Does the CPU have callbacks ready to be invoked? |
| */ |
| static int |
| cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp) |
| { |
| return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL]; |
| } |
| |
| /* |
| * Does the current CPU require a yet-as-unscheduled grace period? |
| */ |
| static int |
| cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp) |
| { |
| return *rdp->nxttail[RCU_DONE_TAIL] && !rcu_gp_in_progress(rsp); |
| } |
| |
| /* |
| * Return the root node of the specified rcu_state structure. |
| */ |
| static struct rcu_node *rcu_get_root(struct rcu_state *rsp) |
| { |
| return &rsp->node[0]; |
| } |
| |
| /* |
| * Record the specified "completed" value, which is later used to validate |
| * dynticks counter manipulations and CPU-offline checks. Specify |
| * "rsp->completed - 1" to unconditionally invalidate any future dynticks |
| * manipulations and CPU-offline checks. Such invalidation is useful at |
| * the beginning of a grace period. |
| */ |
| static void dyntick_record_completed(struct rcu_state *rsp, long comp) |
| { |
| rsp->dynticks_completed = comp; |
| } |
| |
| #ifdef CONFIG_SMP |
| |
| /* |
| * Recall the previously recorded value of the completion for dynticks. |
| */ |
| static long dyntick_recall_completed(struct rcu_state *rsp) |
| { |
| return rsp->dynticks_completed; |
| } |
| |
| /* |
| * If the specified CPU is offline, tell the caller that it is in |
| * a quiescent state. Otherwise, whack it with a reschedule IPI. |
| * Grace periods can end up waiting on an offline CPU when that |
| * CPU is in the process of coming online -- it will be added to the |
| * rcu_node bitmasks before it actually makes it online. The same thing |
| * can happen while a CPU is in the process of coming online. Because this |
| * race is quite rare, we check for it after detecting that the grace |
| * period has been delayed rather than checking each and every CPU |
| * each and every time we start a new grace period. |
| */ |
| static int rcu_implicit_offline_qs(struct rcu_data *rdp) |
| { |
| /* |
| * If the CPU is offline, it is in a quiescent state. We can |
| * trust its state not to change because interrupts are disabled. |
| */ |
| if (cpu_is_offline(rdp->cpu)) { |
| rdp->offline_fqs++; |
| return 1; |
| } |
| |
| /* If preemptable RCU, no point in sending reschedule IPI. */ |
| if (rdp->preemptable) |
| return 0; |
| |
| /* The CPU is online, so send it a reschedule IPI. */ |
| if (rdp->cpu != smp_processor_id()) |
| smp_send_reschedule(rdp->cpu); |
| else |
| set_need_resched(); |
| rdp->resched_ipi++; |
| return 0; |
| } |
| |
| #endif /* #ifdef CONFIG_SMP */ |
| |
| #ifdef CONFIG_NO_HZ |
| |
| /** |
| * rcu_enter_nohz - inform RCU that current CPU is entering nohz |
| * |
| * Enter nohz mode, in other words, -leave- the mode in which RCU |
| * read-side critical sections can occur. (Though RCU read-side |
| * critical sections can occur in irq handlers in nohz mode, a possibility |
| * handled by rcu_irq_enter() and rcu_irq_exit()). |
| */ |
| void rcu_enter_nohz(void) |
| { |
| unsigned long flags; |
| struct rcu_dynticks *rdtp; |
| |
| smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ |
| local_irq_save(flags); |
| rdtp = &__get_cpu_var(rcu_dynticks); |
| rdtp->dynticks++; |
| rdtp->dynticks_nesting--; |
| WARN_ON_ONCE(rdtp->dynticks & 0x1); |
| local_irq_restore(flags); |
| } |
| |
| /* |
| * rcu_exit_nohz - inform RCU that current CPU is leaving nohz |
| * |
| * Exit nohz mode, in other words, -enter- the mode in which RCU |
| * read-side critical sections normally occur. |
| */ |
| void rcu_exit_nohz(void) |
| { |
| unsigned long flags; |
| struct rcu_dynticks *rdtp; |
| |
| local_irq_save(flags); |
| rdtp = &__get_cpu_var(rcu_dynticks); |
| rdtp->dynticks++; |
| rdtp->dynticks_nesting++; |
| WARN_ON_ONCE(!(rdtp->dynticks & 0x1)); |
| local_irq_restore(flags); |
| smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ |
| } |
| |
| /** |
| * rcu_nmi_enter - inform RCU of entry to NMI context |
| * |
| * If the CPU was idle with dynamic ticks active, and there is no |
| * irq handler running, this updates rdtp->dynticks_nmi to let the |
| * RCU grace-period handling know that the CPU is active. |
| */ |
| void rcu_nmi_enter(void) |
| { |
| struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); |
| |
| if (rdtp->dynticks & 0x1) |
| return; |
| rdtp->dynticks_nmi++; |
| WARN_ON_ONCE(!(rdtp->dynticks_nmi & 0x1)); |
| smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ |
| } |
| |
| /** |
| * rcu_nmi_exit - inform RCU of exit from NMI context |
| * |
| * If the CPU was idle with dynamic ticks active, and there is no |
| * irq handler running, this updates rdtp->dynticks_nmi to let the |
| * RCU grace-period handling know that the CPU is no longer active. |
| */ |
| void rcu_nmi_exit(void) |
| { |
| struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); |
| |
| if (rdtp->dynticks & 0x1) |
| return; |
| smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ |
| rdtp->dynticks_nmi++; |
| WARN_ON_ONCE(rdtp->dynticks_nmi & 0x1); |
| } |
| |
| /** |
| * rcu_irq_enter - inform RCU of entry to hard irq context |
| * |
| * If the CPU was idle with dynamic ticks active, this updates the |
| * rdtp->dynticks to let the RCU handling know that the CPU is active. |
| */ |
| void rcu_irq_enter(void) |
| { |
| struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); |
| |
| if (rdtp->dynticks_nesting++) |
| return; |
| rdtp->dynticks++; |
| WARN_ON_ONCE(!(rdtp->dynticks & 0x1)); |
| smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ |
| } |
| |
| /** |
| * rcu_irq_exit - inform RCU of exit from hard irq context |
| * |
| * If the CPU was idle with dynamic ticks active, update the rdp->dynticks |
| * to put let the RCU handling be aware that the CPU is going back to idle |
| * with no ticks. |
| */ |
| void rcu_irq_exit(void) |
| { |
| struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); |
| |
| if (--rdtp->dynticks_nesting) |
| return; |
| smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ |
| rdtp->dynticks++; |
| WARN_ON_ONCE(rdtp->dynticks & 0x1); |
| |
| /* If the interrupt queued a callback, get out of dyntick mode. */ |
| if (__get_cpu_var(rcu_sched_data).nxtlist || |
| __get_cpu_var(rcu_bh_data).nxtlist) |
| set_need_resched(); |
| } |
| |
| #ifdef CONFIG_SMP |
| |
| /* |
| * Snapshot the specified CPU's dynticks counter so that we can later |
| * credit them with an implicit quiescent state. Return 1 if this CPU |
| * is in dynticks idle mode, which is an extended quiescent state. |
| */ |
| static int dyntick_save_progress_counter(struct rcu_data *rdp) |
| { |
| int ret; |
| int snap; |
| int snap_nmi; |
| |
| snap = rdp->dynticks->dynticks; |
| snap_nmi = rdp->dynticks->dynticks_nmi; |
| smp_mb(); /* Order sampling of snap with end of grace period. */ |
| rdp->dynticks_snap = snap; |
| rdp->dynticks_nmi_snap = snap_nmi; |
| ret = ((snap & 0x1) == 0) && ((snap_nmi & 0x1) == 0); |
| if (ret) |
| rdp->dynticks_fqs++; |
| return ret; |
| } |
| |
| /* |
| * 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. |
| */ |
| static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) |
| { |
| long curr; |
| long curr_nmi; |
| long snap; |
| long snap_nmi; |
| |
| curr = rdp->dynticks->dynticks; |
| snap = rdp->dynticks_snap; |
| curr_nmi = rdp->dynticks->dynticks_nmi; |
| snap_nmi = rdp->dynticks_nmi_snap; |
| smp_mb(); /* force ordering with cpu entering/leaving dynticks. */ |
| |
| /* |
| * If the CPU passed through or entered a dynticks idle phase with |
| * no active irq/NMI handlers, then we can safely pretend that the CPU |
| * already acknowledged the request to pass through a quiescent |
| * state. Either way, that CPU cannot possibly be in an RCU |
| * read-side critical section that started before the beginning |
| * of the current RCU grace period. |
| */ |
| if ((curr != snap || (curr & 0x1) == 0) && |
| (curr_nmi != snap_nmi || (curr_nmi & 0x1) == 0)) { |
| rdp->dynticks_fqs++; |
| return 1; |
| } |
| |
| /* Go check for the CPU being offline. */ |
| return rcu_implicit_offline_qs(rdp); |
| } |
| |
| #endif /* #ifdef CONFIG_SMP */ |
| |
| #else /* #ifdef CONFIG_NO_HZ */ |
| |
| #ifdef CONFIG_SMP |
| |
| static int dyntick_save_progress_counter(struct rcu_data *rdp) |
| { |
| return 0; |
| } |
| |
| static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) |
| { |
| return rcu_implicit_offline_qs(rdp); |
| } |
| |
| #endif /* #ifdef CONFIG_SMP */ |
| |
| #endif /* #else #ifdef CONFIG_NO_HZ */ |
| |
| #ifdef CONFIG_RCU_CPU_STALL_DETECTOR |
| |
| static void record_gp_stall_check_time(struct rcu_state *rsp) |
| { |
| rsp->gp_start = jiffies; |
| rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_CHECK; |
| } |
| |
| static void print_other_cpu_stall(struct rcu_state *rsp) |
| { |
| int cpu; |
| long delta; |
| unsigned long flags; |
| struct rcu_node *rnp = rcu_get_root(rsp); |
| |
| /* Only let one CPU complain about others per time interval. */ |
| |
| spin_lock_irqsave(&rnp->lock, flags); |
| delta = jiffies - rsp->jiffies_stall; |
| if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) { |
| spin_unlock_irqrestore(&rnp->lock, flags); |
| return; |
| } |
| rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_RECHECK; |
| |
| /* |
| * Now rat on any tasks that got kicked up to the root rcu_node |
| * due to CPU offlining. |
| */ |
| rcu_print_task_stall(rnp); |
| spin_unlock_irqrestore(&rnp->lock, flags); |
| |
| /* OK, time to rat on our buddy... */ |
| |
| printk(KERN_ERR "INFO: RCU detected CPU stalls:"); |
| rcu_for_each_leaf_node(rsp, rnp) { |
| rcu_print_task_stall(rnp); |
| if (rnp->qsmask == 0) |
| continue; |
| for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++) |
| if (rnp->qsmask & (1UL << cpu)) |
| printk(" %d", rnp->grplo + cpu); |
| } |
| printk(" (detected by %d, t=%ld jiffies)\n", |
| smp_processor_id(), (long)(jiffies - rsp->gp_start)); |
| trigger_all_cpu_backtrace(); |
| |
| force_quiescent_state(rsp, 0); /* Kick them all. */ |
| } |
| |
| static void print_cpu_stall(struct rcu_state *rsp) |
| { |
| unsigned long flags; |
| struct rcu_node *rnp = rcu_get_root(rsp); |
| |
| printk(KERN_ERR "INFO: RCU detected CPU %d stall (t=%lu jiffies)\n", |
| smp_processor_id(), jiffies - rsp->gp_start); |
| trigger_all_cpu_backtrace(); |
| |
| spin_lock_irqsave(&rnp->lock, flags); |
| if ((long)(jiffies - rsp->jiffies_stall) >= 0) |
| rsp->jiffies_stall = |
| jiffies + RCU_SECONDS_TILL_STALL_RECHECK; |
| spin_unlock_irqrestore(&rnp->lock, flags); |
| |
| set_need_resched(); /* kick ourselves to get things going. */ |
| } |
| |
| static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) |
| { |
| long delta; |
| struct rcu_node *rnp; |
| |
| delta = jiffies - rsp->jiffies_stall; |
| rnp = rdp->mynode; |
| if ((rnp->qsmask & rdp->grpmask) && delta >= 0) { |
| |
| /* We haven't checked in, so go dump stack. */ |
| print_cpu_stall(rsp); |
| |
| } else if (rcu_gp_in_progress(rsp) && delta >= RCU_STALL_RAT_DELAY) { |
| |
| /* They had two time units to dump stack, so complain. */ |
| print_other_cpu_stall(rsp); |
| } |
| } |
| |
| #else /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ |
| |
| static void record_gp_stall_check_time(struct rcu_state *rsp) |
| { |
| } |
| |
| static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) |
| { |
| } |
| |
| #endif /* #else #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ |
| |
| /* |
| * Update CPU-local rcu_data state to record the newly noticed grace period. |
| * This is used both when we started the grace period and when we notice |
| * that someone else started the grace period. The caller must hold the |
| * ->lock of the leaf rcu_node structure corresponding to the current CPU, |
| * and must have irqs disabled. |
| */ |
| static void __note_new_gpnum(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) |
| { |
| if (rdp->gpnum != rnp->gpnum) { |
| rdp->qs_pending = 1; |
| rdp->passed_quiesc = 0; |
| rdp->gpnum = rnp->gpnum; |
| } |
| } |
| |
| static void note_new_gpnum(struct rcu_state *rsp, struct rcu_data *rdp) |
| { |
| unsigned long flags; |
| struct rcu_node *rnp; |
| |
| local_irq_save(flags); |
| rnp = rdp->mynode; |
| if (rdp->gpnum == ACCESS_ONCE(rnp->gpnum) || /* outside lock. */ |
| !spin_trylock(&rnp->lock)) { /* irqs already off, retry later. */ |
| local_irq_restore(flags); |
| return; |
| } |
| __note_new_gpnum(rsp, rnp, rdp); |
| spin_unlock_irqrestore(&rnp->lock, flags); |
| } |
| |
| /* |
| * Did someone else start a new RCU grace period start since we last |
| * checked? Update local state appropriately if so. Must be called |
| * on the CPU corresponding to rdp. |
| */ |
| static int |
| check_for_new_grace_period(struct rcu_state *rsp, struct rcu_data *rdp) |
| { |
| unsigned long flags; |
| int ret = 0; |
| |
| local_irq_save(flags); |
| if (rdp->gpnum != rsp->gpnum) { |
| note_new_gpnum(rsp, rdp); |
| ret = 1; |
| } |
| local_irq_restore(flags); |
| return ret; |
| } |
| |
| /* |
| * Advance this CPU's callbacks, but only if the current grace period |
| * has ended. This may be called only from the CPU to whom the rdp |
| * belongs. In addition, the corresponding leaf rcu_node structure's |
| * ->lock must be held by the caller, with irqs disabled. |
| */ |
| static void |
| __rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) |
| { |
| /* Did another grace period end? */ |
| if (rdp->completed != rnp->completed) { |
| |
| /* Advance callbacks. No harm if list empty. */ |
| rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[RCU_WAIT_TAIL]; |
| rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_READY_TAIL]; |
| rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
| |
| /* Remember that we saw this grace-period completion. */ |
| rdp->completed = rnp->completed; |
| } |
| } |
| |
| /* |
| * Advance this CPU's callbacks, but only if the current grace period |
| * has ended. This may be called only from the CPU to whom the rdp |
| * belongs. |
| */ |
| static void |
| rcu_process_gp_end(struct rcu_state *rsp, struct rcu_data *rdp) |
| { |
| unsigned long flags; |
| struct rcu_node *rnp; |
| |
| local_irq_save(flags); |
| rnp = rdp->mynode; |
| if (rdp->completed == ACCESS_ONCE(rnp->completed) || /* outside lock. */ |
| !spin_trylock(&rnp->lock)) { /* irqs already off, retry later. */ |
| local_irq_restore(flags); |
| return; |
| } |
| __rcu_process_gp_end(rsp, rnp, rdp); |
| spin_unlock_irqrestore(&rnp->lock, flags); |
| } |
| |
| /* |
| * Do per-CPU grace-period initialization for running CPU. The caller |
| * must hold the lock of the leaf rcu_node structure corresponding to |
| * this CPU. |
| */ |
| static void |
| rcu_start_gp_per_cpu(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) |
| { |
| /* Prior grace period ended, so advance callbacks for current CPU. */ |
| __rcu_process_gp_end(rsp, rnp, rdp); |
| |
| /* |
| * Because this CPU just now started the new grace period, we know |
| * that all of its callbacks will be covered by this upcoming grace |
| * period, even the ones that were registered arbitrarily recently. |
| * Therefore, advance all outstanding callbacks to RCU_WAIT_TAIL. |
| * |
| * Other CPUs cannot be sure exactly when the grace period started. |
| * Therefore, their recently registered callbacks must pass through |
| * an additional RCU_NEXT_READY stage, so that they will be handled |
| * by the next RCU grace period. |
| */ |
| rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
| rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
| |
| /* Set state so that this CPU will detect the next quiescent state. */ |
| __note_new_gpnum(rsp, rnp, rdp); |
| } |
| |
| /* |
| * Start a new RCU grace period if warranted, re-initializing the hierarchy |
| * in preparation for detecting the next grace period. The caller must hold |
| * the root node's ->lock, which is released before return. Hard irqs must |
| * be disabled. |
| */ |
| static void |
| rcu_start_gp(struct rcu_state *rsp, unsigned long flags) |
| __releases(rcu_get_root(rsp)->lock) |
| { |
| struct rcu_data *rdp = rsp->rda[smp_processor_id()]; |
| struct rcu_node *rnp = rcu_get_root(rsp); |
| |
| if (!cpu_needs_another_gp(rsp, rdp)) { |
| spin_unlock_irqrestore(&rnp->lock, flags); |
| return; |
| } |
| |
| /* Advance to a new grace period and initialize state. */ |
| rsp->gpnum++; |
| WARN_ON_ONCE(rsp->signaled == RCU_GP_INIT); |
| rsp->signaled = RCU_GP_INIT; /* Hold off force_quiescent_state. */ |
| rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; |
| record_gp_stall_check_time(rsp); |
| dyntick_record_completed(rsp, rsp->completed - 1); |
| |
| /* Special-case the common single-level case. */ |
| if (NUM_RCU_NODES == 1) { |
| rcu_preempt_check_blocked_tasks(rnp); |
| rnp->qsmask = rnp->qsmaskinit; |
| rnp->gpnum = rsp->gpnum; |
| rnp->completed = rsp->completed; |
| rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state OK. */ |
| rcu_start_gp_per_cpu(rsp, rnp, rdp); |
| spin_unlock_irqrestore(&rnp->lock, flags); |
| return; |
| } |
| |
| spin_unlock(&rnp->lock); /* leave irqs disabled. */ |
| |
| |
| /* Exclude any concurrent CPU-hotplug operations. */ |
| spin_lock(&rsp->onofflock); /* irqs already disabled. */ |
| |
| /* |
| * 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. |
| * |
| * Note that the grace period cannot complete until we finish |
| * the initialization process, as there will be at least one |
| * qsmask bit set in the root node until that time, namely the |
| * one corresponding to this CPU, due to the fact that we have |
| * irqs disabled. |
| */ |
| rcu_for_each_node_breadth_first(rsp, rnp) { |
| spin_lock(&rnp->lock); /* irqs already disabled. */ |
| 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); |
| spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
| } |
| |
| rnp = rcu_get_root(rsp); |
| spin_lock(&rnp->lock); /* irqs already disabled. */ |
| rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state now OK. */ |
| spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
| spin_unlock_irqrestore(&rsp->onofflock, flags); |
| } |
| |
| /* |
| * Clean up after the prior grace period and let rcu_start_gp() start up |
| * the next grace period if one is needed. Note that the caller must |
| * hold rnp->lock, as required by rcu_start_gp(), which will release it. |
| */ |
| static void cpu_quiet_msk_finish(struct rcu_state *rsp, unsigned long flags) |
| __releases(rcu_get_root(rsp)->lock) |
| { |
| WARN_ON_ONCE(!rcu_gp_in_progress(rsp)); |
| rsp->completed = rsp->gpnum; |
| rsp->signaled = RCU_GP_IDLE; |
| rcu_start_gp(rsp, flags); /* releases root node's rnp->lock. */ |
| } |
| |
| /* |
| * Similar to cpu_quiet(), for which it is a helper function. Allows |
| * a group of CPUs to be quieted at one go, though all the CPUs in the |
| * group must be represented by the same leaf rcu_node structure. |
| * That structure's lock must be held upon entry, and it is released |
| * before return. |
| */ |
| static void |
| cpu_quiet_msk(unsigned long mask, struct rcu_state *rsp, struct rcu_node *rnp, |
| unsigned long flags) |
| __releases(rnp->lock) |
| { |
| struct rcu_node *rnp_c; |
| |
| /* Walk up the rcu_node hierarchy. */ |
| for (;;) { |
| if (!(rnp->qsmask & mask)) { |
| |
| /* Our bit has already been cleared, so done. */ |
| spin_unlock_irqrestore(&rnp->lock, flags); |
| return; |
| } |
| rnp->qsmask &= ~mask; |
| if (rnp->qsmask != 0 || rcu_preempted_readers(rnp)) { |
| |
| /* Other bits still set at this level, so done. */ |
| spin_unlock_irqrestore(&rnp->lock, flags); |
| return; |
| } |
| mask = rnp->grpmask; |
| if (rnp->parent == NULL) { |
| |
| /* No more levels. Exit loop holding root lock. */ |
| |
| break; |
| } |
| spin_unlock_irqrestore(&rnp->lock, flags); |
| rnp_c = rnp; |
| rnp = rnp->parent; |
| spin_lock_irqsave(&rnp->lock, flags); |
| WARN_ON_ONCE(rnp_c->qsmask); |
| } |
| |
| /* |
| * Get here if we are the last CPU to pass through a quiescent |
| * state for this grace period. Invoke cpu_quiet_msk_finish() |
| * to clean up and start the next grace period if one is needed. |
| */ |
| cpu_quiet_msk_finish(rsp, flags); /* releases rnp->lock. */ |
| } |
| |
| /* |
| * Record a quiescent state for the specified CPU, which must either be |
| * the current CPU. The lastcomp argument is used to make sure we are |
| * still in the grace period of interest. We don't want to end the current |
| * grace period based on quiescent states detected in an earlier grace |
| * period! |
| */ |
| static void |
| cpu_quiet(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastcomp) |
| { |
| unsigned long flags; |
| unsigned long mask; |
| struct rcu_node *rnp; |
| |
| rnp = rdp->mynode; |
| spin_lock_irqsave(&rnp->lock, flags); |
| if (lastcomp != ACCESS_ONCE(rsp->completed)) { |
| |
| /* |
| * Someone beat us to it for this grace period, so leave. |
| * The race with GP start is resolved by the fact that we |
| * hold the leaf rcu_node lock, so that the per-CPU bits |
| * cannot yet be initialized -- so we would simply find our |
| * CPU's bit already cleared in cpu_quiet_msk() if this race |
| * occurred. |
| */ |
| rdp->passed_quiesc = 0; /* try again later! */ |
| spin_unlock_irqrestore(&rnp->lock, flags); |
| return; |
| } |
| mask = rdp->grpmask; |
| if ((rnp->qsmask & mask) == 0) { |
| spin_unlock_irqrestore(&rnp->lock, flags); |
| } else { |
| rdp->qs_pending = 0; |
| |
| /* |
| * This GP can't end until cpu checks in, so all of our |
| * callbacks can be processed during the next GP. |
| */ |
| rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
| |
| cpu_quiet_msk(mask, rsp, rnp, flags); /* releases rnp->lock */ |
| } |
| } |
| |
| /* |
| * Check to see if there is a new grace period of which this CPU |
| * is not yet aware, and if so, set up local rcu_data state for it. |
| * Otherwise, see if this CPU has just passed through its first |
| * quiescent state for this grace period, and record that fact if so. |
| */ |
| static void |
| rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp) |
| { |
| /* If there is now a new grace period, record and return. */ |
| if (check_for_new_grace_period(rsp, rdp)) |
| return; |
| |
| /* |
| * Does this CPU still need to do its part for current grace period? |
| * If no, return and let the other CPUs do their part as well. |
| */ |
| if (!rdp->qs_pending) |
| return; |
| |
| /* |
| * Was there a quiescent state since the beginning of the grace |
| * period? If no, then exit and wait for the next call. |
| */ |
| if (!rdp->passed_quiesc) |
| return; |
| |
| /* Tell RCU we are done (but cpu_quiet() will be the judge of that). */ |
| cpu_quiet(rdp->cpu, rsp, rdp, rdp->passed_quiesc_completed); |
| } |
| |
| #ifdef CONFIG_HOTPLUG_CPU |
| |
| /* |
| * Move a dying CPU's RCU callbacks to the ->orphan_cbs_list for the |
| * specified flavor of RCU. The callbacks will be adopted by the next |
| * _rcu_barrier() invocation or by the CPU_DEAD notifier, whichever |
| * comes first. Because this is invoked from the CPU_DYING notifier, |
| * irqs are already disabled. |
| */ |
| static void rcu_send_cbs_to_orphanage(struct rcu_state *rsp) |
| { |
| int i; |
| struct rcu_data *rdp = rsp->rda[smp_processor_id()]; |
| |
| if (rdp->nxtlist == NULL) |
| return; /* irqs disabled, so comparison is stable. */ |
| spin_lock(&rsp->onofflock); /* irqs already disabled. */ |
| *rsp->orphan_cbs_tail = rdp->nxtlist; |
| rsp->orphan_cbs_tail = rdp->nxttail[RCU_NEXT_TAIL]; |
| rdp->nxtlist = NULL; |
| for (i = 0; i < RCU_NEXT_SIZE; i++) |
| rdp->nxttail[i] = &rdp->nxtlist; |
| rsp->orphan_qlen += rdp->qlen; |
| rdp->qlen = 0; |
| spin_unlock(&rsp->onofflock); /* irqs remain disabled. */ |
| } |
| |
| /* |
| * Adopt previously orphaned RCU callbacks. |
| */ |
| static void rcu_adopt_orphan_cbs(struct rcu_state *rsp) |
| { |
| unsigned long flags; |
| struct rcu_data *rdp; |
| |
| spin_lock_irqsave(&rsp->onofflock, flags); |
| rdp = rsp->rda[smp_processor_id()]; |
| if (rsp->orphan_cbs_list == NULL) { |
| spin_unlock_irqrestore(&rsp->onofflock, flags); |
| return; |
| } |
| *rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_cbs_list; |
| rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_cbs_tail; |
| rdp->qlen += rsp->orphan_qlen; |
| rsp->orphan_cbs_list = NULL; |
| rsp->orphan_cbs_tail = &rsp->orphan_cbs_list; |
| rsp->orphan_qlen = 0; |
| spin_unlock_irqrestore(&rsp->onofflock, flags); |
| } |
| |
| /* |
| * Remove the outgoing CPU from the bitmasks in the rcu_node hierarchy |
| * and move all callbacks from the outgoing CPU to the current one. |
| */ |
| static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp) |
| { |
| unsigned long flags; |
| long lastcomp; |
| unsigned long mask; |
| struct rcu_data *rdp = rsp->rda[cpu]; |
| struct rcu_node *rnp; |
| |
| /* Exclude any attempts to start a new grace period. */ |
| spin_lock_irqsave(&rsp->onofflock, flags); |
| |
| /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */ |
| rnp = rdp->mynode; /* this is the outgoing CPU's rnp. */ |
| mask = rdp->grpmask; /* rnp->grplo is constant. */ |
| do { |
| spin_lock(&rnp->lock); /* irqs already disabled. */ |
| rnp->qsmaskinit &= ~mask; |
| if (rnp->qsmaskinit != 0) { |
| spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
| break; |
| } |
| |
| /* |
| * If there was a task blocking the current grace period, |
| * and if all CPUs have checked in, we need to propagate |
| * the quiescent state up the rcu_node hierarchy. But that |
| * is inconvenient at the moment due to deadlock issues if |
| * this should end the current grace period. So set the |
| * offlined CPU's bit in ->qsmask in order to force the |
| * next force_quiescent_state() invocation to clean up this |
| * mess in a deadlock-free manner. |
| */ |
| if (rcu_preempt_offline_tasks(rsp, rnp, rdp) && !rnp->qsmask) |
| rnp->qsmask |= mask; |
| |
| mask = rnp->grpmask; |
| spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
| rnp = rnp->parent; |
| } while (rnp != NULL); |
| lastcomp = rsp->completed; |
| |
| spin_unlock_irqrestore(&rsp->onofflock, flags); |
| |
| rcu_adopt_orphan_cbs(rsp); |
| } |
| |
| /* |
| * Remove the specified CPU from the RCU hierarchy and move any pending |
| * callbacks that it might have to the current CPU. This code assumes |
| * that at least one CPU in the system will remain running at all times. |
| * Any attempt to offline -all- CPUs is likely to strand RCU callbacks. |
| */ |
| static void rcu_offline_cpu(int cpu) |
| { |
| __rcu_offline_cpu(cpu, &rcu_sched_state); |
| __rcu_offline_cpu(cpu, &rcu_bh_state); |
| rcu_preempt_offline_cpu(cpu); |
| } |
| |
| #else /* #ifdef CONFIG_HOTPLUG_CPU */ |
| |
| static void rcu_send_cbs_to_orphanage(struct rcu_state *rsp) |
| { |
| } |
| |
| static void rcu_adopt_orphan_cbs(struct rcu_state *rsp) |
| { |
| } |
| |
| static void rcu_offline_cpu(int cpu) |
| { |
| } |
| |
| #endif /* #else #ifdef CONFIG_HOTPLUG_CPU */ |
| |
| /* |
| * Invoke any RCU callbacks that have made it to the end of their grace |
| * period. Thottle as specified by rdp->blimit. |
| */ |
| static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp) |
| { |
| unsigned long flags; |
| struct rcu_head *next, *list, **tail; |
| int count; |
| |
| /* If no callbacks are ready, just return.*/ |
| if (!cpu_has_callbacks_ready_to_invoke(rdp)) |
| return; |
| |
| /* |
| * Extract the list of ready callbacks, disabling to prevent |
| * races with call_rcu() from interrupt handlers. |
| */ |
| local_irq_save(flags); |
| list = rdp->nxtlist; |
| rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL]; |
| *rdp->nxttail[RCU_DONE_TAIL] = NULL; |
| tail = rdp->nxttail[RCU_DONE_TAIL]; |
| for (count = RCU_NEXT_SIZE - 1; count >= 0; count--) |
| if (rdp->nxttail[count] == rdp->nxttail[RCU_DONE_TAIL]) |
| rdp->nxttail[count] = &rdp->nxtlist; |
| local_irq_restore(flags); |
| |
| /* Invoke callbacks. */ |
| count = 0; |
| while (list) { |
| next = list->next; |
| prefetch(next); |
| list->func(list); |
| list = next; |
| if (++count >= rdp->blimit) |
| break; |
| } |
| |
| local_irq_save(flags); |
| |
| /* Update count, and requeue any remaining callbacks. */ |
| rdp->qlen -= count; |
| if (list != NULL) { |
| *tail = rdp->nxtlist; |
| rdp->nxtlist = list; |
| for (count = 0; count < RCU_NEXT_SIZE; count++) |
| if (&rdp->nxtlist == rdp->nxttail[count]) |
| rdp->nxttail[count] = tail; |
| else |
| break; |
| } |
| |
| /* Reinstate batch limit if we have worked down the excess. */ |
| if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark) |
| rdp->blimit = blimit; |
| |
| /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */ |
| if (rdp->qlen == 0 && rdp->qlen_last_fqs_check != 0) { |
| rdp->qlen_last_fqs_check = 0; |
| rdp->n_force_qs_snap = rsp->n_force_qs; |
| } else if (rdp->qlen < rdp->qlen_last_fqs_check - qhimark) |
| rdp->qlen_last_fqs_check = rdp->qlen; |
| |
| local_irq_restore(flags); |
| |
| /* Re-raise the RCU softirq if there are callbacks remaining. */ |
| if (cpu_has_callbacks_ready_to_invoke(rdp)) |
| raise_softirq(RCU_SOFTIRQ); |
| } |
| |
| /* |
| * Check to see if this CPU is in a non-context-switch quiescent state |
| * (user mode or idle loop for rcu, non-softirq execution for rcu_bh). |
| * Also schedule the RCU softirq handler. |
| * |
| * This function must be called with hardirqs disabled. It is normally |
| * invoked from the scheduling-clock interrupt. If rcu_pending returns |
| * false, there is no point in invoking rcu_check_callbacks(). |
| */ |
| void rcu_check_callbacks(int cpu, int user) |
| { |
| if (!rcu_pending(cpu)) |
| return; /* if nothing for RCU to do. */ |
| if (user || |
| (idle_cpu(cpu) && rcu_scheduler_active && |
| !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 note it. |
| * |
| * No memory barrier is required here because both |
| * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local |
| * variables that other CPUs neither access nor modify, |
| * at least not while the corresponding CPU is online. |
| */ |
| |
| rcu_sched_qs(cpu); |
| rcu_bh_qs(cpu); |
| |
| } 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 note it. |
| */ |
| |
| rcu_bh_qs(cpu); |
| } |
| rcu_preempt_check_callbacks(cpu); |
| raise_softirq(RCU_SOFTIRQ); |
| } |
| |
| #ifdef CONFIG_SMP |
| |
| /* |
| * Scan the leaf rcu_node structures, processing dyntick state for any that |
| * have not yet encountered a quiescent state, using the function specified. |
| * Returns 1 if the current grace period ends while scanning (possibly |
| * because we made it end). |
| */ |
| static int rcu_process_dyntick(struct rcu_state *rsp, long lastcomp, |
| int (*f)(struct rcu_data *)) |
| { |
| unsigned long bit; |
| int cpu; |
| unsigned long flags; |
| unsigned long mask; |
| struct rcu_node *rnp; |
| |
| rcu_for_each_leaf_node(rsp, rnp) { |
| mask = 0; |
| spin_lock_irqsave(&rnp->lock, flags); |
| if (rsp->completed != lastcomp) { |
| spin_unlock_irqrestore(&rnp->lock, flags); |
| return 1; |
| } |
| if (rnp->qsmask == 0) { |
| spin_unlock_irqrestore(&rnp->lock, flags); |
| continue; |
| } |
| cpu = rnp->grplo; |
| bit = 1; |
| for (; cpu <= rnp->grphi; cpu++, bit <<= 1) { |
| if ((rnp->qsmask & bit) != 0 && f(rsp->rda[cpu])) |
| mask |= bit; |
| } |
| if (mask != 0 && rsp->completed == lastcomp) { |
| |
| /* cpu_quiet_msk() releases rnp->lock. */ |
| cpu_quiet_msk(mask, rsp, rnp, flags); |
| continue; |
| } |
| spin_unlock_irqrestore(&rnp->lock, flags); |
| } |
| return 0; |
| } |
| |
| /* |
| * Force quiescent states on reluctant CPUs, and also detect which |
| * CPUs are in dyntick-idle mode. |
| */ |
| static void force_quiescent_state(struct rcu_state *rsp, int relaxed) |
| { |
| unsigned long flags; |
| long lastcomp; |
| struct rcu_node *rnp = rcu_get_root(rsp); |
| u8 signaled; |
| u8 forcenow; |
| |
| if (!rcu_gp_in_progress(rsp)) |
| return; /* No grace period in progress, nothing to force. */ |
| if (!spin_trylock_irqsave(&rsp->fqslock, flags)) { |
| rsp->n_force_qs_lh++; /* Inexact, can lose counts. Tough! */ |
| return; /* Someone else is already on the job. */ |
| } |
| if (relaxed && |
| (long)(rsp->jiffies_force_qs - jiffies) >= 0) |
| goto unlock_ret; /* no emergency and done recently. */ |
| rsp->n_force_qs++; |
| spin_lock(&rnp->lock); |
| lastcomp = rsp->completed; |
| signaled = rsp->signaled; |
| rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; |
| if (lastcomp == rsp->gpnum) { |
| rsp->n_force_qs_ngp++; |
| spin_unlock(&rnp->lock); |
| goto unlock_ret; /* no GP in progress, time updated. */ |
| } |
| spin_unlock(&rnp->lock); |
| switch (signaled) { |
| case RCU_GP_IDLE: |
| case RCU_GP_INIT: |
| |
| break; /* grace period idle or initializing, ignore. */ |
| |
| case RCU_SAVE_DYNTICK: |
| |
| if (RCU_SIGNAL_INIT != RCU_SAVE_DYNTICK) |
| break; /* So gcc recognizes the dead code. */ |
| |
| /* Record dyntick-idle state. */ |
| if (rcu_process_dyntick(rsp, lastcomp, |
| dyntick_save_progress_counter)) |
| goto unlock_ret; |
| /* fall into next case. */ |
| |
| case RCU_SAVE_COMPLETED: |
| |
| /* Update state, record completion counter. */ |
| forcenow = 0; |
| spin_lock(&rnp->lock); |
| if (lastcomp == rsp->completed && |
| rsp->signaled == signaled) { |
| rsp->signaled = RCU_FORCE_QS; |
| dyntick_record_completed(rsp, lastcomp); |
| forcenow = signaled == RCU_SAVE_COMPLETED; |
| } |
| spin_unlock(&rnp->lock); |
| if (!forcenow) |
| break; |
| /* fall into next case. */ |
| |
| case RCU_FORCE_QS: |
| |
| /* Check dyntick-idle state, send IPI to laggarts. */ |
| if (rcu_process_dyntick(rsp, dyntick_recall_completed(rsp), |
| rcu_implicit_dynticks_qs)) |
| goto unlock_ret; |
| |
| /* Leave state in case more forcing is required. */ |
| |
| break; |
| } |
| unlock_ret: |
| spin_unlock_irqrestore(&rsp->fqslock, flags); |
| } |
| |
| #else /* #ifdef CONFIG_SMP */ |
| |
| static void force_quiescent_state(struct rcu_state *rsp, int relaxed) |
| { |
| set_need_resched(); |
| } |
| |
| #endif /* #else #ifdef CONFIG_SMP */ |
| |
| /* |
| * This does the RCU processing work from softirq context for the |
| * specified rcu_state and rcu_data structures. This may be called |
| * only from the CPU to whom the rdp belongs. |
| */ |
| static void |
| __rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) |
| { |
| unsigned long flags; |
| |
| WARN_ON_ONCE(rdp->beenonline == 0); |
| |
| /* |
| * If an RCU GP has gone long enough, go check for dyntick |
| * idle CPUs and, if needed, send resched IPIs. |
| */ |
| if ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0) |
| force_quiescent_state(rsp, 1); |
| |
| /* |
| * Advance callbacks in response to end of earlier grace |
| * period that some other CPU ended. |
| */ |
| rcu_process_gp_end(rsp, rdp); |
| |
| /* Update RCU state based on any recent quiescent states. */ |
| rcu_check_quiescent_state(rsp, rdp); |
| |
| /* Does this CPU require a not-yet-started grace period? */ |
| if (cpu_needs_another_gp(rsp, rdp)) { |
| spin_lock_irqsave(&rcu_get_root(rsp)->lock, flags); |
| rcu_start_gp(rsp, flags); /* releases above lock */ |
| } |
| |
| /* If there are callbacks ready, invoke them. */ |
| rcu_do_batch(rsp, rdp); |
| } |
| |
| /* |
| * Do softirq processing for the current CPU. |
| */ |
| static void rcu_process_callbacks(struct softirq_action *unused) |
| { |
| /* |
| * Memory references from any prior RCU read-side critical sections |
| * executed by the interrupted code must be seen before any RCU |
| * grace-period manipulations below. |
| */ |
| smp_mb(); /* See above block comment. */ |
| |
| __rcu_process_callbacks(&rcu_sched_state, |
| &__get_cpu_var(rcu_sched_data)); |
| __rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data)); |
| rcu_preempt_process_callbacks(); |
| |
| /* |
| * Memory references from any later RCU read-side critical sections |
| * executed by the interrupted code must be seen after any RCU |
| * grace-period manipulations above. |
| */ |
| smp_mb(); /* See above block comment. */ |
| } |
| |
| static void |
| __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), |
| struct rcu_state *rsp) |
| { |
| unsigned long flags; |
| struct rcu_data *rdp; |
| |
| head->func = func; |
| head->next = NULL; |
| |
| smp_mb(); /* Ensure RCU update seen before callback registry. */ |
| |
| /* |
| * Opportunistically note grace-period endings and beginnings. |
| * Note that we might see a beginning right after we see an |
| * end, but never vice versa, since this CPU has to pass through |
| * a quiescent state betweentimes. |
| */ |
| local_irq_save(flags); |
| rdp = rsp->rda[smp_processor_id()]; |
| rcu_process_gp_end(rsp, rdp); |
| check_for_new_grace_period(rsp, rdp); |
| |
| /* Add the callback to our list. */ |
| *rdp->nxttail[RCU_NEXT_TAIL] = head; |
| rdp->nxttail[RCU_NEXT_TAIL] = &head->next; |
| |
| /* Start a new grace period if one not already started. */ |
| if (!rcu_gp_in_progress(rsp)) { |
| unsigned long nestflag; |
| struct rcu_node *rnp_root = rcu_get_root(rsp); |
| |
| spin_lock_irqsave(&rnp_root->lock, nestflag); |
| rcu_start_gp(rsp, nestflag); /* releases rnp_root->lock. */ |
| } |
| |
| /* |
| * Force the grace period if too many callbacks or too long waiting. |
| * Enforce hysteresis, and don't invoke force_quiescent_state() |
| * if some other CPU has recently done so. Also, don't bother |
| * invoking force_quiescent_state() if the newly enqueued callback |
| * is the only one waiting for a grace period to complete. |
| */ |
| if (unlikely(++rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) { |
| rdp->blimit = LONG_MAX; |
| if (rsp->n_force_qs == rdp->n_force_qs_snap && |
| *rdp->nxttail[RCU_DONE_TAIL] != head) |
| force_quiescent_state(rsp, 0); |
| rdp->n_force_qs_snap = rsp->n_force_qs; |
| rdp->qlen_last_fqs_check = rdp->qlen; |
| } else if ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0) |
| force_quiescent_state(rsp, 1); |
| local_irq_restore(flags); |
| } |
| |
| /* |
| * Queue an RCU-sched callback for invocation after a grace period. |
| */ |
| void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
| { |
| __call_rcu(head, func, &rcu_sched_state); |
| } |
| EXPORT_SYMBOL_GPL(call_rcu_sched); |
| |
| /* |
| * Queue an RCU for invocation after a quicker grace period. |
| */ |
| void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
| { |
| __call_rcu(head, func, &rcu_bh_state); |
| } |
| EXPORT_SYMBOL_GPL(call_rcu_bh); |
| |
| /* |
| * Check to see if there is any immediate RCU-related work to be done |
| * by the current CPU, for the specified type of RCU, returning 1 if so. |
| * The checks are in order of increasing expense: checks that can be |
| * carried out against CPU-local state are performed first. However, |
| * we must check for CPU stalls first, else we might not get a chance. |
| */ |
| static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) |
| { |
| rdp->n_rcu_pending++; |
| |
| /* Check for CPU stalls, if enabled. */ |
| check_cpu_stall(rsp, rdp); |
| |
| /* Is the RCU core waiting for a quiescent state from this CPU? */ |
| if (rdp->qs_pending) { |
| rdp->n_rp_qs_pending++; |
| return 1; |
| } |
| |
| /* Does this CPU have callbacks ready to invoke? */ |
| if (cpu_has_callbacks_ready_to_invoke(rdp)) { |
| rdp->n_rp_cb_ready++; |
| return 1; |
| } |
| |
| /* Has RCU gone idle with this CPU needing another grace period? */ |
| if (cpu_needs_another_gp(rsp, rdp)) { |
| rdp->n_rp_cpu_needs_gp++; |
| return 1; |
| } |
| |
| /* Has another RCU grace period completed? */ |
| if (ACCESS_ONCE(rsp->completed) != rdp->completed) { /* outside lock */ |
| rdp->n_rp_gp_completed++; |
| return 1; |
| } |
| |
| /* Has a new RCU grace period started? */ |
| if (ACCESS_ONCE(rsp->gpnum) != rdp->gpnum) { /* outside lock */ |
| rdp->n_rp_gp_started++; |
| return 1; |
| } |
| |
| /* Has an RCU GP gone long enough to send resched IPIs &c? */ |
| if (rcu_gp_in_progress(rsp) && |
| ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0)) { |
| rdp->n_rp_need_fqs++; |
| return 1; |
| } |
| |
| /* nothing to do */ |
| rdp->n_rp_need_nothing++; |
| return 0; |
| } |
| |
| /* |
| * Check to see if there is any immediate RCU-related work to be done |
| * by the current CPU, returning 1 if so. This function is part of the |
| * RCU implementation; it is -not- an exported member of the RCU API. |
| */ |
| static int rcu_pending(int cpu) |
| { |
| return __rcu_pending(&rcu_sched_state, &per_cpu(rcu_sched_data, cpu)) || |
| __rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, cpu)) || |
| rcu_preempt_pending(cpu); |
| } |
| |
| /* |
| * Check to see if any future RCU-related work will need to be done |
| * by the current CPU, even if none need be done immediately, returning |
| * 1 if so. This function is part of the RCU implementation; it is -not- |
| * an exported member of the RCU API. |
| */ |
| int rcu_needs_cpu(int cpu) |
| { |
| /* RCU callbacks either ready or pending? */ |
| return per_cpu(rcu_sched_data, cpu).nxtlist || |
| per_cpu(rcu_bh_data, cpu).nxtlist || |
| rcu_preempt_needs_cpu(cpu); |
| } |
| |
| static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL}; |
| static atomic_t rcu_barrier_cpu_count; |
| static DEFINE_MUTEX(rcu_barrier_mutex); |
| static struct completion rcu_barrier_completion; |
| |
| static void rcu_barrier_callback(struct rcu_head *notused) |
| { |
| if (atomic_dec_and_test(&rcu_barrier_cpu_count)) |
| complete(&rcu_barrier_completion); |
| } |
| |
| /* |
| * Called with preemption disabled, and from cross-cpu IRQ context. |
| */ |
| static void rcu_barrier_func(void *type) |
| { |
| int cpu = smp_processor_id(); |
| struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu); |
| void (*call_rcu_func)(struct rcu_head *head, |
| void (*func)(struct rcu_head *head)); |
| |
| atomic_inc(&rcu_barrier_cpu_count); |
| call_rcu_func = type; |
| call_rcu_func(head, rcu_barrier_callback); |
| } |
| |
| /* |
| * Orchestrate the specified type of RCU barrier, waiting for all |
| * RCU callbacks of the specified type to complete. |
| */ |
| static void _rcu_barrier(struct rcu_state *rsp, |
| void (*call_rcu_func)(struct rcu_head *head, |
| void (*func)(struct rcu_head *head))) |
| { |
| BUG_ON(in_interrupt()); |
| /* Take mutex to serialize concurrent rcu_barrier() requests. */ |
| mutex_lock(&rcu_barrier_mutex); |
| init_completion(&rcu_barrier_completion); |
| /* |
| * Initialize rcu_barrier_cpu_count to 1, then invoke |
| * rcu_barrier_func() on each CPU, so that each CPU also has |
| * incremented rcu_barrier_cpu_count. Only then is it safe to |
| * decrement rcu_barrier_cpu_count -- otherwise the first CPU |
| * might complete its grace period before all of the other CPUs |
| * did their increment, causing this function to return too |
| * early. |
| */ |
| atomic_set(&rcu_barrier_cpu_count, 1); |
| preempt_disable(); /* stop CPU_DYING from filling orphan_cbs_list */ |
| rcu_adopt_orphan_cbs(rsp); |
| on_each_cpu(rcu_barrier_func, (void *)call_rcu_func, 1); |
| preempt_enable(); /* CPU_DYING can again fill orphan_cbs_list */ |
| if (atomic_dec_and_test(&rcu_barrier_cpu_count)) |
| complete(&rcu_barrier_completion); |
| wait_for_completion(&rcu_barrier_completion); |
| mutex_unlock(&rcu_barrier_mutex); |
| } |
| |
| /** |
| * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete. |
| */ |
| void rcu_barrier_bh(void) |
| { |
| _rcu_barrier(&rcu_bh_state, call_rcu_bh); |
| } |
| EXPORT_SYMBOL_GPL(rcu_barrier_bh); |
| |
| /** |
| * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks. |
| */ |
| void rcu_barrier_sched(void) |
| { |
| _rcu_barrier(&rcu_sched_state, call_rcu_sched); |
| } |
| EXPORT_SYMBOL_GPL(rcu_barrier_sched); |
| |
| /* |
| * Do boot-time initialization of a CPU's per-CPU RCU data. |
| */ |
| static void __init |
| rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) |
| { |
| unsigned long flags; |
| int i; |
| struct rcu_data *rdp = rsp->rda[cpu]; |
| struct rcu_node *rnp = rcu_get_root(rsp); |
| |
| /* Set up local state, ensuring consistent view of global state. */ |
| spin_lock_irqsave(&rnp->lock, flags); |
| rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo); |
| rdp->nxtlist = NULL; |
| for (i = 0; i < RCU_NEXT_SIZE; i++) |
| rdp->nxttail[i] = &rdp->nxtlist; |
| rdp->qlen = 0; |
| #ifdef CONFIG_NO_HZ |
| rdp->dynticks = &per_cpu(rcu_dynticks, cpu); |
| #endif /* #ifdef CONFIG_NO_HZ */ |
| rdp->cpu = cpu; |
| spin_unlock_irqrestore(&rnp->lock, flags); |
| } |
| |
| /* |
| * Initialize a CPU's per-CPU RCU data. Note that only one online or |
| * offline event can be happening at a given time. Note also that we |
| * can accept some slop in the rsp->completed access due to the fact |
| * that this CPU cannot possibly have any RCU callbacks in flight yet. |
| */ |
| static void __cpuinit |
| rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptable) |
| { |
| unsigned long flags; |
| unsigned long mask; |
| struct rcu_data *rdp = rsp->rda[cpu]; |
| struct rcu_node *rnp = rcu_get_root(rsp); |
| |
| /* Set up local state, ensuring consistent view of global state. */ |
| spin_lock_irqsave(&rnp->lock, flags); |
| rdp->passed_quiesc = 0; /* We could be racing with new GP, */ |
| rdp->qs_pending = 1; /* so set up to respond to current GP. */ |
| rdp->beenonline = 1; /* We have now been online. */ |
| rdp->preemptable = preemptable; |
| rdp->qlen_last_fqs_check = 0; |
| rdp->n_force_qs_snap = rsp->n_force_qs; |
| rdp->blimit = blimit; |
| spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
| |
| /* |
| * A new grace period might start here. If so, we won't be part |
| * of it, but that is OK, as we are currently in a quiescent state. |
| */ |
| |
| /* Exclude any attempts to start a new GP on large systems. */ |
| spin_lock(&rsp->onofflock); /* irqs already disabled. */ |
| |
| /* Add CPU to rcu_node bitmasks. */ |
| rnp = rdp->mynode; |
| mask = rdp->grpmask; |
| do { |
| /* Exclude any attempts to start a new GP on small systems. */ |
| spin_lock(&rnp->lock); /* irqs already disabled. */ |
| rnp->qsmaskinit |= mask; |
| mask = rnp->grpmask; |
| if (rnp == rdp->mynode) { |
| rdp->gpnum = rnp->completed; /* if GP in progress... */ |
| rdp->completed = rnp->completed; |
| rdp->passed_quiesc_completed = rnp->completed - 1; |
| } |
| spin_unlock(&rnp->lock); /* irqs already disabled. */ |
| rnp = rnp->parent; |
| } while (rnp != NULL && !(rnp->qsmaskinit & mask)); |
| |
| spin_unlock_irqrestore(&rsp->onofflock, flags); |
| } |
| |
| static void __cpuinit rcu_online_cpu(int cpu) |
| { |
| rcu_init_percpu_data(cpu, &rcu_sched_state, 0); |
| rcu_init_percpu_data(cpu, &rcu_bh_state, 0); |
| rcu_preempt_init_percpu_data(cpu); |
| } |
| |
| /* |
| * Handle CPU online/offline notification events. |
| */ |
| int __cpuinit rcu_cpu_notify(struct notifier_block *self, |
| unsigned long action, void *hcpu) |
| { |
| long cpu = (long)hcpu; |
| |
| switch (action) { |
| case CPU_UP_PREPARE: |
| case CPU_UP_PREPARE_FROZEN: |
| rcu_online_cpu(cpu); |
| break; |
| case CPU_DYING: |
| case CPU_DYING_FROZEN: |
| /* |
| * preempt_disable() in _rcu_barrier() prevents stop_machine(), |
| * so when "on_each_cpu(rcu_barrier_func, (void *)type, 1);" |
| * returns, all online cpus have queued rcu_barrier_func(). |
| * The dying CPU clears its cpu_online_mask bit and |
| * moves all of its RCU callbacks to ->orphan_cbs_list |
| * in the context of stop_machine(), so subsequent calls |
| * to _rcu_barrier() will adopt these callbacks and only |
| * then queue rcu_barrier_func() on all remaining CPUs. |
| */ |
| rcu_send_cbs_to_orphanage(&rcu_bh_state); |
| rcu_send_cbs_to_orphanage(&rcu_sched_state); |
| rcu_preempt_send_cbs_to_orphanage(); |
| break; |
| case CPU_DEAD: |
| case CPU_DEAD_FROZEN: |
| case CPU_UP_CANCELED: |
| case CPU_UP_CANCELED_FROZEN: |
| rcu_offline_cpu(cpu); |
| break; |
| default: |
| break; |
| } |
| return NOTIFY_OK; |
| } |
| |
| /* |
| * Compute the per-level fanout, either using the exact fanout specified |
| * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT. |
| */ |
| #ifdef CONFIG_RCU_FANOUT_EXACT |
| static void __init rcu_init_levelspread(struct rcu_state *rsp) |
| { |
| int i; |
| |
| for (i = NUM_RCU_LVLS - 1; i >= 0; i--) |
| rsp->levelspread[i] = CONFIG_RCU_FANOUT; |
| } |
| #else /* #ifdef CONFIG_RCU_FANOUT_EXACT */ |
| static void __init rcu_init_levelspread(struct rcu_state *rsp) |
| { |
| int ccur; |
| int cprv; |
| int i; |
| |
| cprv = NR_CPUS; |
| for (i = NUM_RCU_LVLS - 1; i >= 0; i--) { |
| ccur = rsp->levelcnt[i]; |
| rsp->levelspread[i] = (cprv + ccur - 1) / ccur; |
| cprv = ccur; |
| } |
| } |
| #endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */ |
| |
| /* |
| * Helper function for rcu_init() that initializes one rcu_state structure. |
| */ |
| static void __init rcu_init_one(struct rcu_state *rsp) |
| { |
| int cpustride = 1; |
| int i; |
| int j; |
| struct rcu_node *rnp; |
| |
| /* Initialize the level-tracking arrays. */ |
| |
| for (i = 1; i < NUM_RCU_LVLS; i++) |
| rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1]; |
| rcu_init_levelspread(rsp); |
| |
| /* Initialize the elements themselves, starting from the leaves. */ |
| |
| for (i = NUM_RCU_LVLS - 1; i >= 0; i--) { |
| cpustride *= rsp->levelspread[i]; |
| rnp = rsp->level[i]; |
| for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) { |
| if (rnp != rcu_get_root(rsp)) |
| spin_lock_init(&rnp->lock); |
| rnp->gpnum = 0; |
| rnp->qsmask = 0; |
| rnp->qsmaskinit = 0; |
| rnp->grplo = j * cpustride; |
| rnp->grphi = (j + 1) * cpustride - 1; |
| if (rnp->grphi >= NR_CPUS) |
| rnp->grphi = NR_CPUS - 1; |
| if (i == 0) { |
| rnp->grpnum = 0; |
| rnp->grpmask = 0; |
| rnp->parent = NULL; |
| } else { |
| rnp->grpnum = j % rsp->levelspread[i - 1]; |
| rnp->grpmask = 1UL << rnp->grpnum; |
| rnp->parent = rsp->level[i - 1] + |
| j / rsp->levelspread[i - 1]; |
| } |
| rnp->level = i; |
| INIT_LIST_HEAD(&rnp->blocked_tasks[0]); |
| INIT_LIST_HEAD(&rnp->blocked_tasks[1]); |
| } |
| } |
| spin_lock_init(&rcu_get_root(rsp)->lock); |
| } |
| |
| /* |
| * Helper macro for __rcu_init() and __rcu_init_preempt(). To be used |
| * nowhere else! Assigns leaf node pointers into each CPU's rcu_data |
| * structure. |
| */ |
| #define RCU_INIT_FLAVOR(rsp, rcu_data) \ |
| do { \ |
| int i; \ |
| int j; \ |
| struct rcu_node *rnp; \ |
| \ |
| rcu_init_one(rsp); \ |
| rnp = (rsp)->level[NUM_RCU_LVLS - 1]; \ |
| j = 0; \ |
| for_each_possible_cpu(i) { \ |
| if (i > rnp[j].grphi) \ |
| j++; \ |
| per_cpu(rcu_data, i).mynode = &rnp[j]; \ |
| (rsp)->rda[i] = &per_cpu(rcu_data, i); \ |
| rcu_boot_init_percpu_data(i, rsp); \ |
| } \ |
| } while (0) |
| |
| void __init __rcu_init(void) |
| { |
| rcu_bootup_announce(); |
| #ifdef CONFIG_RCU_CPU_STALL_DETECTOR |
| printk(KERN_INFO "RCU-based detection of stalled CPUs is enabled.\n"); |
| #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ |
| RCU_INIT_FLAVOR(&rcu_sched_state, rcu_sched_data); |
| RCU_INIT_FLAVOR(&rcu_bh_state, rcu_bh_data); |
| __rcu_init_preempt(); |
| open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); |
| } |
| |
| #include "rcutree_plugin.h" |