diff options
Diffstat (limited to 'kernel/rcu/tree_exp.h')
| -rw-r--r-- | kernel/rcu/tree_exp.h | 235 |
1 files changed, 139 insertions, 96 deletions
diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h index f72eefab8543..d40708e8c5d6 100644 --- a/kernel/rcu/tree_exp.h +++ b/kernel/rcu/tree_exp.h @@ -20,6 +20,8 @@ * Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com> */ +#include <linux/lockdep.h> + /* * Record the start of an expedited grace period. */ @@ -154,15 +156,35 @@ static void __maybe_unused sync_exp_reset_tree(struct rcu_state *rsp) * for the current expedited grace period. Works only for preemptible * RCU -- other RCU implementation use other means. * - * Caller must hold the rcu_state's exp_mutex. + * Caller must hold the specificed rcu_node structure's ->lock */ static bool sync_rcu_preempt_exp_done(struct rcu_node *rnp) { + raw_lockdep_assert_held_rcu_node(rnp); + return rnp->exp_tasks == NULL && READ_ONCE(rnp->expmask) == 0; } /* + * Like sync_rcu_preempt_exp_done(), but this function assumes the caller + * doesn't hold the rcu_node's ->lock, and will acquire and release the lock + * itself + */ +static bool sync_rcu_preempt_exp_done_unlocked(struct rcu_node *rnp) +{ + unsigned long flags; + bool ret; + + raw_spin_lock_irqsave_rcu_node(rnp, flags); + ret = sync_rcu_preempt_exp_done(rnp); + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + + return ret; +} + + +/* * Report the exit from RCU read-side critical section for the last task * that queued itself during or before the current expedited preemptible-RCU * grace period. This event is reported either to the rcu_node structure on @@ -170,8 +192,7 @@ static bool sync_rcu_preempt_exp_done(struct rcu_node *rnp) * recursively up the tree. (Calm down, calm down, we do the recursion * iteratively!) * - * Caller must hold the rcu_state's exp_mutex and the specified rcu_node - * structure's ->lock. + * Caller must hold the specified rcu_node structure's ->lock. */ static void __rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp, bool wake, unsigned long flags) @@ -207,8 +228,6 @@ static void __rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp, /* * Report expedited quiescent state for specified node. This is a * lock-acquisition wrapper function for __rcu_report_exp_rnp(). - * - * Caller must hold the rcu_state's exp_mutex. */ static void __maybe_unused rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp, bool wake) @@ -221,8 +240,7 @@ static void __maybe_unused rcu_report_exp_rnp(struct rcu_state *rsp, /* * Report expedited quiescent state for multiple CPUs, all covered by the - * specified leaf rcu_node structure. Caller must hold the rcu_state's - * exp_mutex. + * specified leaf rcu_node structure. */ static void rcu_report_exp_cpu_mult(struct rcu_state *rsp, struct rcu_node *rnp, unsigned long mask, bool wake) @@ -248,14 +266,12 @@ static void rcu_report_exp_rdp(struct rcu_state *rsp, struct rcu_data *rdp, } /* Common code for synchronize_{rcu,sched}_expedited() work-done checking. */ -static bool sync_exp_work_done(struct rcu_state *rsp, atomic_long_t *stat, - unsigned long s) +static bool sync_exp_work_done(struct rcu_state *rsp, unsigned long s) { if (rcu_exp_gp_seq_done(rsp, s)) { trace_rcu_exp_grace_period(rsp->name, s, TPS("done")); /* Ensure test happens before caller kfree(). */ smp_mb__before_atomic(); /* ^^^ */ - atomic_long_inc(stat); return true; } return false; @@ -289,7 +305,7 @@ static bool exp_funnel_lock(struct rcu_state *rsp, unsigned long s) * promoting locality and is not strictly needed for correctness. */ for (; rnp != NULL; rnp = rnp->parent) { - if (sync_exp_work_done(rsp, &rdp->exp_workdone1, s)) + if (sync_exp_work_done(rsp, s)) return true; /* Work not done, either wait here or go up. */ @@ -302,8 +318,7 @@ static bool exp_funnel_lock(struct rcu_state *rsp, unsigned long s) rnp->grplo, rnp->grphi, TPS("wait")); wait_event(rnp->exp_wq[rcu_seq_ctr(s) & 0x3], - sync_exp_work_done(rsp, - &rdp->exp_workdone2, s)); + sync_exp_work_done(rsp, s)); return true; } rnp->exp_seq_rq = s; /* Followers can wait on us. */ @@ -313,7 +328,7 @@ static bool exp_funnel_lock(struct rcu_state *rsp, unsigned long s) } mutex_lock(&rsp->exp_mutex); fastpath: - if (sync_exp_work_done(rsp, &rdp->exp_workdone3, s)) { + if (sync_exp_work_done(rsp, s)) { mutex_unlock(&rsp->exp_mutex); return true; } @@ -362,93 +377,129 @@ static void sync_sched_exp_online_cleanup(int cpu) } /* - * Select the nodes that the upcoming expedited grace period needs - * to wait for. + * Select the CPUs within the specified rcu_node that the upcoming + * expedited grace period needs to wait for. */ -static void sync_rcu_exp_select_cpus(struct rcu_state *rsp, - smp_call_func_t func) +static void sync_rcu_exp_select_node_cpus(struct work_struct *wp) { int cpu; unsigned long flags; + smp_call_func_t func; unsigned long mask_ofl_test; unsigned long mask_ofl_ipi; int ret; - struct rcu_node *rnp; - - trace_rcu_exp_grace_period(rsp->name, rcu_exp_gp_seq_endval(rsp), TPS("reset")); - sync_exp_reset_tree(rsp); - trace_rcu_exp_grace_period(rsp->name, rcu_exp_gp_seq_endval(rsp), TPS("select")); - rcu_for_each_leaf_node(rsp, rnp) { - raw_spin_lock_irqsave_rcu_node(rnp, flags); + struct rcu_exp_work *rewp = + container_of(wp, struct rcu_exp_work, rew_work); + struct rcu_node *rnp = container_of(rewp, struct rcu_node, rew); + struct rcu_state *rsp = rewp->rew_rsp; - /* Each pass checks a CPU for identity, offline, and idle. */ - mask_ofl_test = 0; - for_each_leaf_node_cpu_mask(rnp, cpu, rnp->expmask) { - unsigned long mask = leaf_node_cpu_bit(rnp, cpu); - struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); - struct rcu_dynticks *rdtp = per_cpu_ptr(&rcu_dynticks, cpu); - int snap; + func = rewp->rew_func; + raw_spin_lock_irqsave_rcu_node(rnp, flags); - if (raw_smp_processor_id() == cpu || - !(rnp->qsmaskinitnext & mask)) { + /* Each pass checks a CPU for identity, offline, and idle. */ + mask_ofl_test = 0; + for_each_leaf_node_cpu_mask(rnp, cpu, rnp->expmask) { + unsigned long mask = leaf_node_cpu_bit(rnp, cpu); + struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); + struct rcu_dynticks *rdtp = per_cpu_ptr(&rcu_dynticks, cpu); + int snap; + + if (raw_smp_processor_id() == cpu || + !(rnp->qsmaskinitnext & mask)) { + mask_ofl_test |= mask; + } else { + snap = rcu_dynticks_snap(rdtp); + if (rcu_dynticks_in_eqs(snap)) mask_ofl_test |= mask; - } else { - snap = rcu_dynticks_snap(rdtp); - if (rcu_dynticks_in_eqs(snap)) - mask_ofl_test |= mask; - else - rdp->exp_dynticks_snap = snap; - } + else + rdp->exp_dynticks_snap = snap; } - mask_ofl_ipi = rnp->expmask & ~mask_ofl_test; - - /* - * Need to wait for any blocked tasks as well. Note that - * additional blocking tasks will also block the expedited - * GP until such time as the ->expmask bits are cleared. - */ - if (rcu_preempt_has_tasks(rnp)) - rnp->exp_tasks = rnp->blkd_tasks.next; - raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + } + mask_ofl_ipi = rnp->expmask & ~mask_ofl_test; - /* IPI the remaining CPUs for expedited quiescent state. */ - for_each_leaf_node_cpu_mask(rnp, cpu, rnp->expmask) { - unsigned long mask = leaf_node_cpu_bit(rnp, cpu); - struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); + /* + * Need to wait for any blocked tasks as well. Note that + * additional blocking tasks will also block the expedited GP + * until such time as the ->expmask bits are cleared. + */ + if (rcu_preempt_has_tasks(rnp)) + rnp->exp_tasks = rnp->blkd_tasks.next; + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); - if (!(mask_ofl_ipi & mask)) - continue; + /* IPI the remaining CPUs for expedited quiescent state. */ + for_each_leaf_node_cpu_mask(rnp, cpu, rnp->expmask) { + unsigned long mask = leaf_node_cpu_bit(rnp, cpu); + struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); + + if (!(mask_ofl_ipi & mask)) + continue; retry_ipi: - if (rcu_dynticks_in_eqs_since(rdp->dynticks, - rdp->exp_dynticks_snap)) { - mask_ofl_test |= mask; - continue; - } - ret = smp_call_function_single(cpu, func, rsp, 0); - if (!ret) { - mask_ofl_ipi &= ~mask; - continue; - } - /* Failed, raced with CPU hotplug operation. */ - raw_spin_lock_irqsave_rcu_node(rnp, flags); - if ((rnp->qsmaskinitnext & mask) && - (rnp->expmask & mask)) { - /* Online, so delay for a bit and try again. */ - raw_spin_unlock_irqrestore_rcu_node(rnp, flags); - trace_rcu_exp_grace_period(rsp->name, rcu_exp_gp_seq_endval(rsp), TPS("selectofl")); - schedule_timeout_uninterruptible(1); - goto retry_ipi; - } - /* CPU really is offline, so we can ignore it. */ - if (!(rnp->expmask & mask)) - mask_ofl_ipi &= ~mask; + if (rcu_dynticks_in_eqs_since(rdp->dynticks, + rdp->exp_dynticks_snap)) { + mask_ofl_test |= mask; + continue; + } + ret = smp_call_function_single(cpu, func, rsp, 0); + if (!ret) { + mask_ofl_ipi &= ~mask; + continue; + } + /* Failed, raced with CPU hotplug operation. */ + raw_spin_lock_irqsave_rcu_node(rnp, flags); + if ((rnp->qsmaskinitnext & mask) && + (rnp->expmask & mask)) { + /* Online, so delay for a bit and try again. */ raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + trace_rcu_exp_grace_period(rsp->name, rcu_exp_gp_seq_endval(rsp), TPS("selectofl")); + schedule_timeout_uninterruptible(1); + goto retry_ipi; + } + /* CPU really is offline, so we can ignore it. */ + if (!(rnp->expmask & mask)) + mask_ofl_ipi &= ~mask; + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + } + /* Report quiescent states for those that went offline. */ + mask_ofl_test |= mask_ofl_ipi; + if (mask_ofl_test) + rcu_report_exp_cpu_mult(rsp, rnp, mask_ofl_test, false); +} + +/* + * Select the nodes that the upcoming expedited grace period needs + * to wait for. + */ +static void sync_rcu_exp_select_cpus(struct rcu_state *rsp, + smp_call_func_t func) +{ + struct rcu_node *rnp; + + trace_rcu_exp_grace_period(rsp->name, rcu_exp_gp_seq_endval(rsp), TPS("reset")); + sync_exp_reset_tree(rsp); + trace_rcu_exp_grace_period(rsp->name, rcu_exp_gp_seq_endval(rsp), TPS("select")); + + /* Schedule work for each leaf rcu_node structure. */ + rcu_for_each_leaf_node(rsp, rnp) { + rnp->exp_need_flush = false; + if (!READ_ONCE(rnp->expmask)) + continue; /* Avoid early boot non-existent wq. */ + rnp->rew.rew_func = func; + rnp->rew.rew_rsp = rsp; + if (!READ_ONCE(rcu_par_gp_wq) || + rcu_scheduler_active != RCU_SCHEDULER_RUNNING) { + /* No workqueues yet. */ + sync_rcu_exp_select_node_cpus(&rnp->rew.rew_work); + continue; } - /* Report quiescent states for those that went offline. */ - mask_ofl_test |= mask_ofl_ipi; - if (mask_ofl_test) - rcu_report_exp_cpu_mult(rsp, rnp, mask_ofl_test, false); + INIT_WORK(&rnp->rew.rew_work, sync_rcu_exp_select_node_cpus); + queue_work_on(rnp->grplo, rcu_par_gp_wq, &rnp->rew.rew_work); + rnp->exp_need_flush = true; } + + /* Wait for workqueue jobs (if any) to complete. */ + rcu_for_each_leaf_node(rsp, rnp) + if (rnp->exp_need_flush) + flush_work(&rnp->rew.rew_work); } static void synchronize_sched_expedited_wait(struct rcu_state *rsp) @@ -469,9 +520,9 @@ static void synchronize_sched_expedited_wait(struct rcu_state *rsp) for (;;) { ret = swait_event_timeout( rsp->expedited_wq, - sync_rcu_preempt_exp_done(rnp_root), + sync_rcu_preempt_exp_done_unlocked(rnp_root), jiffies_stall); - if (ret > 0 || sync_rcu_preempt_exp_done(rnp_root)) + if (ret > 0 || sync_rcu_preempt_exp_done_unlocked(rnp_root)) return; WARN_ON(ret < 0); /* workqueues should not be signaled. */ if (rcu_cpu_stall_suppress) @@ -504,7 +555,7 @@ static void synchronize_sched_expedited_wait(struct rcu_state *rsp) rcu_for_each_node_breadth_first(rsp, rnp) { if (rnp == rnp_root) continue; /* printed unconditionally */ - if (sync_rcu_preempt_exp_done(rnp)) + if (sync_rcu_preempt_exp_done_unlocked(rnp)) continue; pr_cont(" l=%u:%d-%d:%#lx/%c", rnp->level, rnp->grplo, rnp->grphi, @@ -560,14 +611,6 @@ static void rcu_exp_wait_wake(struct rcu_state *rsp, unsigned long s) mutex_unlock(&rsp->exp_wake_mutex); } -/* Let the workqueue handler know what it is supposed to do. */ -struct rcu_exp_work { - smp_call_func_t rew_func; - struct rcu_state *rew_rsp; - unsigned long rew_s; - struct work_struct rew_work; -}; - /* * Common code to drive an expedited grace period forward, used by * workqueues and mid-boot-time tasks. @@ -633,7 +676,7 @@ static void _synchronize_rcu_expedited(struct rcu_state *rsp, rdp = per_cpu_ptr(rsp->rda, raw_smp_processor_id()); rnp = rcu_get_root(rsp); wait_event(rnp->exp_wq[rcu_seq_ctr(s) & 0x3], - sync_exp_work_done(rsp, &rdp->exp_workdone0, s)); + sync_exp_work_done(rsp, s)); smp_mb(); /* Workqueue actions happen before return. */ /* Let the next expedited grace period start. */ |