diff options
Diffstat (limited to 'kernel/rcu/tree.c')
| -rw-r--r-- | kernel/rcu/tree.c | 508 |
1 files changed, 14 insertions, 494 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index acd6ccf56faf..ec77ec336f58 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -102,11 +102,6 @@ int rcu_num_lvls __read_mostly = RCU_NUM_LVLS; /* Number of rcu_nodes at specified level. */ int num_rcu_lvl[] = NUM_RCU_LVL_INIT; int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */ -/* panic() on RCU Stall sysctl. */ -int sysctl_panic_on_rcu_stall __read_mostly; -/* Commandeer a sysrq key to dump RCU's tree. */ -static bool sysrq_rcu; -module_param(sysrq_rcu, bool, 0444); /* * The rcu_scheduler_active variable is initialized to the value @@ -149,7 +144,7 @@ static void sync_sched_exp_online_cleanup(int cpu); /* rcuc/rcub kthread realtime priority */ static int kthread_prio = IS_ENABLED(CONFIG_RCU_BOOST) ? 1 : 0; -module_param(kthread_prio, int, 0644); +module_param(kthread_prio, int, 0444); /* Delay in jiffies for grace-period initialization delays, debug only. */ @@ -406,7 +401,7 @@ static bool rcu_kick_kthreads; */ static ulong jiffies_till_sched_qs = ULONG_MAX; module_param(jiffies_till_sched_qs, ulong, 0444); -static ulong jiffies_to_sched_qs; /* Adjusted version of above if not default */ +static ulong jiffies_to_sched_qs; /* See adjust_jiffies_till_sched_qs(). */ module_param(jiffies_to_sched_qs, ulong, 0444); /* Display only! */ /* @@ -424,6 +419,7 @@ static void adjust_jiffies_till_sched_qs(void) WRITE_ONCE(jiffies_to_sched_qs, jiffies_till_sched_qs); return; } + /* Otherwise, set to third fqs scan, but bound below on large system. */ j = READ_ONCE(jiffies_till_first_fqs) + 2 * READ_ONCE(jiffies_till_next_fqs); if (j < HZ / 10 + nr_cpu_ids / RCU_JIFFIES_FQS_DIV) @@ -513,74 +509,6 @@ static const char *gp_state_getname(short gs) } /* - * Show the state of the grace-period kthreads. - */ -void show_rcu_gp_kthreads(void) -{ - int cpu; - unsigned long j; - unsigned long ja; - unsigned long jr; - unsigned long jw; - struct rcu_data *rdp; - struct rcu_node *rnp; - - j = jiffies; - ja = j - READ_ONCE(rcu_state.gp_activity); - jr = j - READ_ONCE(rcu_state.gp_req_activity); - jw = j - READ_ONCE(rcu_state.gp_wake_time); - pr_info("%s: wait state: %s(%d) ->state: %#lx delta ->gp_activity %lu ->gp_req_activity %lu ->gp_wake_time %lu ->gp_wake_seq %ld ->gp_seq %ld ->gp_seq_needed %ld ->gp_flags %#x\n", - rcu_state.name, gp_state_getname(rcu_state.gp_state), - rcu_state.gp_state, - rcu_state.gp_kthread ? rcu_state.gp_kthread->state : 0x1ffffL, - ja, jr, jw, (long)READ_ONCE(rcu_state.gp_wake_seq), - (long)READ_ONCE(rcu_state.gp_seq), - (long)READ_ONCE(rcu_get_root()->gp_seq_needed), - READ_ONCE(rcu_state.gp_flags)); - rcu_for_each_node_breadth_first(rnp) { - if (ULONG_CMP_GE(rcu_state.gp_seq, rnp->gp_seq_needed)) - continue; - pr_info("\trcu_node %d:%d ->gp_seq %ld ->gp_seq_needed %ld\n", - rnp->grplo, rnp->grphi, (long)rnp->gp_seq, - (long)rnp->gp_seq_needed); - if (!rcu_is_leaf_node(rnp)) - continue; - for_each_leaf_node_possible_cpu(rnp, cpu) { - rdp = per_cpu_ptr(&rcu_data, cpu); - if (rdp->gpwrap || - ULONG_CMP_GE(rcu_state.gp_seq, - rdp->gp_seq_needed)) - continue; - pr_info("\tcpu %d ->gp_seq_needed %ld\n", - cpu, (long)rdp->gp_seq_needed); - } - } - /* sched_show_task(rcu_state.gp_kthread); */ -} -EXPORT_SYMBOL_GPL(show_rcu_gp_kthreads); - -/* Dump grace-period-request information due to commandeered sysrq. */ -static void sysrq_show_rcu(int key) -{ - show_rcu_gp_kthreads(); -} - -static struct sysrq_key_op sysrq_rcudump_op = { - .handler = sysrq_show_rcu, - .help_msg = "show-rcu(y)", - .action_msg = "Show RCU tree", - .enable_mask = SYSRQ_ENABLE_DUMP, -}; - -static int __init rcu_sysrq_init(void) -{ - if (sysrq_rcu) - return register_sysrq_key('y', &sysrq_rcudump_op); - return 0; -} -early_initcall(rcu_sysrq_init); - -/* * Send along grace-period-related data for rcutorture diagnostics. */ void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags, @@ -1034,27 +962,6 @@ static int dyntick_save_progress_counter(struct rcu_data *rdp) } /* - * Handler for the irq_work request posted when a grace period has - * gone on for too long, but not yet long enough for an RCU CPU - * stall warning. Set state appropriately, but just complain if - * there is unexpected state on entry. - */ -static void rcu_iw_handler(struct irq_work *iwp) -{ - struct rcu_data *rdp; - struct rcu_node *rnp; - - rdp = container_of(iwp, struct rcu_data, rcu_iw); - rnp = rdp->mynode; - raw_spin_lock_rcu_node(rnp); - if (!WARN_ON_ONCE(!rdp->rcu_iw_pending)) { - rdp->rcu_iw_gp_seq = rnp->gp_seq; - rdp->rcu_iw_pending = false; - } - raw_spin_unlock_rcu_node(rnp); -} - -/* * 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() @@ -1167,295 +1074,6 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) return 0; } -static void record_gp_stall_check_time(void) -{ - unsigned long j = jiffies; - unsigned long j1; - - rcu_state.gp_start = j; - j1 = rcu_jiffies_till_stall_check(); - /* Record ->gp_start before ->jiffies_stall. */ - smp_store_release(&rcu_state.jiffies_stall, j + j1); /* ^^^ */ - rcu_state.jiffies_resched = j + j1 / 2; - rcu_state.n_force_qs_gpstart = READ_ONCE(rcu_state.n_force_qs); -} - -/* - * Complain about starvation of grace-period kthread. - */ -static void rcu_check_gp_kthread_starvation(void) -{ - struct task_struct *gpk = rcu_state.gp_kthread; - unsigned long j; - - j = jiffies - READ_ONCE(rcu_state.gp_activity); - if (j > 2 * HZ) { - pr_err("%s kthread starved for %ld jiffies! g%ld f%#x %s(%d) ->state=%#lx ->cpu=%d\n", - rcu_state.name, j, - (long)rcu_seq_current(&rcu_state.gp_seq), - READ_ONCE(rcu_state.gp_flags), - gp_state_getname(rcu_state.gp_state), rcu_state.gp_state, - gpk ? gpk->state : ~0, gpk ? task_cpu(gpk) : -1); - if (gpk) { - pr_err("RCU grace-period kthread stack dump:\n"); - sched_show_task(gpk); - wake_up_process(gpk); - } - } -} - -/* - * Dump stacks of all tasks running on stalled CPUs. First try using - * NMIs, but fall back to manual remote stack tracing on architectures - * that don't support NMI-based stack dumps. The NMI-triggered stack - * traces are more accurate because they are printed by the target CPU. - */ -static void rcu_dump_cpu_stacks(void) -{ - int cpu; - unsigned long flags; - struct rcu_node *rnp; - - rcu_for_each_leaf_node(rnp) { - raw_spin_lock_irqsave_rcu_node(rnp, flags); - for_each_leaf_node_possible_cpu(rnp, cpu) - if (rnp->qsmask & leaf_node_cpu_bit(rnp, cpu)) - if (!trigger_single_cpu_backtrace(cpu)) - dump_cpu_task(cpu); - raw_spin_unlock_irqrestore_rcu_node(rnp, flags); - } -} - -/* - * If too much time has passed in the current grace period, and if - * so configured, go kick the relevant kthreads. - */ -static void rcu_stall_kick_kthreads(void) -{ - unsigned long j; - - if (!rcu_kick_kthreads) - return; - j = READ_ONCE(rcu_state.jiffies_kick_kthreads); - if (time_after(jiffies, j) && rcu_state.gp_kthread && - (rcu_gp_in_progress() || READ_ONCE(rcu_state.gp_flags))) { - WARN_ONCE(1, "Kicking %s grace-period kthread\n", - rcu_state.name); - rcu_ftrace_dump(DUMP_ALL); - wake_up_process(rcu_state.gp_kthread); - WRITE_ONCE(rcu_state.jiffies_kick_kthreads, j + HZ); - } -} - -static void panic_on_rcu_stall(void) -{ - if (sysctl_panic_on_rcu_stall) - panic("RCU Stall\n"); -} - -static void print_other_cpu_stall(unsigned long gp_seq) -{ - int cpu; - unsigned long flags; - unsigned long gpa; - unsigned long j; - int ndetected = 0; - struct rcu_node *rnp = rcu_get_root(); - long totqlen = 0; - - /* Kick and suppress, if so configured. */ - rcu_stall_kick_kthreads(); - if (rcu_cpu_stall_suppress) - return; - - /* - * OK, time to rat on our buddy... - * See Documentation/RCU/stallwarn.txt for info on how to debug - * RCU CPU stall warnings. - */ - pr_err("INFO: %s detected stalls on CPUs/tasks:", rcu_state.name); - print_cpu_stall_info_begin(); - rcu_for_each_leaf_node(rnp) { - raw_spin_lock_irqsave_rcu_node(rnp, flags); - ndetected += rcu_print_task_stall(rnp); - if (rnp->qsmask != 0) { - for_each_leaf_node_possible_cpu(rnp, cpu) - if (rnp->qsmask & leaf_node_cpu_bit(rnp, cpu)) { - print_cpu_stall_info(cpu); - ndetected++; - } - } - raw_spin_unlock_irqrestore_rcu_node(rnp, flags); - } - - print_cpu_stall_info_end(); - for_each_possible_cpu(cpu) - totqlen += rcu_get_n_cbs_cpu(cpu); - pr_cont("(detected by %d, t=%ld jiffies, g=%ld, q=%lu)\n", - smp_processor_id(), (long)(jiffies - rcu_state.gp_start), - (long)rcu_seq_current(&rcu_state.gp_seq), totqlen); - if (ndetected) { - rcu_dump_cpu_stacks(); - - /* Complain about tasks blocking the grace period. */ - rcu_print_detail_task_stall(); - } else { - if (rcu_seq_current(&rcu_state.gp_seq) != gp_seq) { - pr_err("INFO: Stall ended before state dump start\n"); - } else { - j = jiffies; - gpa = READ_ONCE(rcu_state.gp_activity); - pr_err("All QSes seen, last %s kthread activity %ld (%ld-%ld), jiffies_till_next_fqs=%ld, root ->qsmask %#lx\n", - rcu_state.name, j - gpa, j, gpa, - READ_ONCE(jiffies_till_next_fqs), - rcu_get_root()->qsmask); - /* In this case, the current CPU might be at fault. */ - sched_show_task(current); - } - } - /* Rewrite if needed in case of slow consoles. */ - if (ULONG_CMP_GE(jiffies, READ_ONCE(rcu_state.jiffies_stall))) - WRITE_ONCE(rcu_state.jiffies_stall, - jiffies + 3 * rcu_jiffies_till_stall_check() + 3); - - rcu_check_gp_kthread_starvation(); - - panic_on_rcu_stall(); - - rcu_force_quiescent_state(); /* Kick them all. */ -} - -static void print_cpu_stall(void) -{ - int cpu; - unsigned long flags; - struct rcu_data *rdp = this_cpu_ptr(&rcu_data); - struct rcu_node *rnp = rcu_get_root(); - long totqlen = 0; - - /* Kick and suppress, if so configured. */ - rcu_stall_kick_kthreads(); - if (rcu_cpu_stall_suppress) - return; - - /* - * OK, time to rat on ourselves... - * See Documentation/RCU/stallwarn.txt for info on how to debug - * RCU CPU stall warnings. - */ - pr_err("INFO: %s self-detected stall on CPU", rcu_state.name); - print_cpu_stall_info_begin(); - raw_spin_lock_irqsave_rcu_node(rdp->mynode, flags); - print_cpu_stall_info(smp_processor_id()); - raw_spin_unlock_irqrestore_rcu_node(rdp->mynode, flags); - print_cpu_stall_info_end(); - for_each_possible_cpu(cpu) - totqlen += rcu_get_n_cbs_cpu(cpu); - pr_cont(" (t=%lu jiffies g=%ld q=%lu)\n", - jiffies - rcu_state.gp_start, - (long)rcu_seq_current(&rcu_state.gp_seq), totqlen); - - rcu_check_gp_kthread_starvation(); - - rcu_dump_cpu_stacks(); - - raw_spin_lock_irqsave_rcu_node(rnp, flags); - /* Rewrite if needed in case of slow consoles. */ - if (ULONG_CMP_GE(jiffies, READ_ONCE(rcu_state.jiffies_stall))) - WRITE_ONCE(rcu_state.jiffies_stall, - jiffies + 3 * rcu_jiffies_till_stall_check() + 3); - raw_spin_unlock_irqrestore_rcu_node(rnp, flags); - - panic_on_rcu_stall(); - - /* - * Attempt to revive the RCU machinery by forcing a context switch. - * - * A context switch would normally allow the RCU state machine to make - * progress and it could be we're stuck in kernel space without context - * switches for an entirely unreasonable amount of time. - */ - set_tsk_need_resched(current); - set_preempt_need_resched(); -} - -static void check_cpu_stall(struct rcu_data *rdp) -{ - unsigned long gs1; - unsigned long gs2; - unsigned long gps; - unsigned long j; - unsigned long jn; - unsigned long js; - struct rcu_node *rnp; - - if ((rcu_cpu_stall_suppress && !rcu_kick_kthreads) || - !rcu_gp_in_progress()) - return; - rcu_stall_kick_kthreads(); - j = jiffies; - - /* - * Lots of memory barriers to reject false positives. - * - * The idea is to pick up rcu_state.gp_seq, then - * rcu_state.jiffies_stall, then rcu_state.gp_start, and finally - * another copy of rcu_state.gp_seq. These values are updated in - * the opposite order with memory barriers (or equivalent) during - * grace-period initialization and cleanup. Now, a false positive - * can occur if we get an new value of rcu_state.gp_start and a old - * value of rcu_state.jiffies_stall. But given the memory barriers, - * the only way that this can happen is if one grace period ends - * and another starts between these two fetches. This is detected - * by comparing the second fetch of rcu_state.gp_seq with the - * previous fetch from rcu_state.gp_seq. - * - * Given this check, comparisons of jiffies, rcu_state.jiffies_stall, - * and rcu_state.gp_start suffice to forestall false positives. - */ - gs1 = READ_ONCE(rcu_state.gp_seq); - smp_rmb(); /* Pick up ->gp_seq first... */ - js = READ_ONCE(rcu_state.jiffies_stall); - smp_rmb(); /* ...then ->jiffies_stall before the rest... */ - gps = READ_ONCE(rcu_state.gp_start); - smp_rmb(); /* ...and finally ->gp_start before ->gp_seq again. */ - gs2 = READ_ONCE(rcu_state.gp_seq); - if (gs1 != gs2 || - ULONG_CMP_LT(j, js) || - ULONG_CMP_GE(gps, js)) - return; /* No stall or GP completed since entering function. */ - rnp = rdp->mynode; - jn = jiffies + 3 * rcu_jiffies_till_stall_check() + 3; - if (rcu_gp_in_progress() && - (READ_ONCE(rnp->qsmask) & rdp->grpmask) && - cmpxchg(&rcu_state.jiffies_stall, js, jn) == js) { - - /* We haven't checked in, so go dump stack. */ - print_cpu_stall(); - - } else if (rcu_gp_in_progress() && - ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY) && - cmpxchg(&rcu_state.jiffies_stall, js, jn) == js) { - - /* They had a few time units to dump stack, so complain. */ - print_other_cpu_stall(gs2); - } -} - -/** - * rcu_cpu_stall_reset - prevent further stall warnings in current grace period - * - * Set the stall-warning timeout way off into the future, thus preventing - * any RCU CPU stall-warning messages from appearing in the current set of - * RCU grace periods. - * - * The caller must disable hard irqs. - */ -void rcu_cpu_stall_reset(void) -{ - WRITE_ONCE(rcu_state.jiffies_stall, jiffies + ULONG_MAX / 2); -} - /* Trace-event wrapper function for trace_rcu_future_grace_period. */ static void trace_rcu_this_gp(struct rcu_node *rnp, struct rcu_data *rdp, unsigned long gp_seq_req, const char *s) @@ -1585,7 +1203,7 @@ static bool rcu_future_gp_cleanup(struct rcu_node *rnp) static void rcu_gp_kthread_wake(void) { if ((current == rcu_state.gp_kthread && - !in_interrupt() && !in_serving_softirq()) || + !in_irq() && !in_serving_softirq()) || !READ_ONCE(rcu_state.gp_flags) || !rcu_state.gp_kthread) return; @@ -2295,11 +1913,10 @@ rcu_report_qs_rdp(int cpu, struct rcu_data *rdp) return; } mask = rdp->grpmask; + rdp->core_needs_qs = false; if ((rnp->qsmask & mask) == 0) { raw_spin_unlock_irqrestore_rcu_node(rnp, flags); } else { - rdp->core_needs_qs = false; - /* * This GP can't end until cpu checks in, so all of our * callbacks can be processed during the next GP. @@ -2548,11 +2165,11 @@ void rcu_sched_clock_irq(int user) } /* - * Scan the leaf rcu_node structures, processing dyntick state for any that - * have not yet encountered a quiescent state, using the function specified. - * Also initiate boosting for any threads blocked on the root rcu_node. - * - * The caller must have suppressed start of new grace periods. + * Scan the leaf rcu_node structures. For each structure on which all + * CPUs have reported a quiescent state and on which there are tasks + * blocking the current grace period, initiate RCU priority boosting. + * Otherwise, invoke the specified function to check dyntick state for + * each CPU that has not yet reported a quiescent state. */ static void force_qs_rnp(int (*f)(struct rcu_data *rdp)) { @@ -2635,101 +2252,6 @@ void rcu_force_quiescent_state(void) } EXPORT_SYMBOL_GPL(rcu_force_quiescent_state); -/* - * This function checks for grace-period requests that fail to motivate - * RCU to come out of its idle mode. - */ -void -rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp, - const unsigned long gpssdelay) -{ - unsigned long flags; - unsigned long j; - struct rcu_node *rnp_root = rcu_get_root(); - static atomic_t warned = ATOMIC_INIT(0); - - if (!IS_ENABLED(CONFIG_PROVE_RCU) || rcu_gp_in_progress() || - ULONG_CMP_GE(rnp_root->gp_seq, rnp_root->gp_seq_needed)) - return; - j = jiffies; /* Expensive access, and in common case don't get here. */ - if (time_before(j, READ_ONCE(rcu_state.gp_req_activity) + gpssdelay) || - time_before(j, READ_ONCE(rcu_state.gp_activity) + gpssdelay) || - atomic_read(&warned)) - return; - - raw_spin_lock_irqsave_rcu_node(rnp, flags); - j = jiffies; - if (rcu_gp_in_progress() || - ULONG_CMP_GE(rnp_root->gp_seq, rnp_root->gp_seq_needed) || - time_before(j, READ_ONCE(rcu_state.gp_req_activity) + gpssdelay) || - time_before(j, READ_ONCE(rcu_state.gp_activity) + gpssdelay) || - atomic_read(&warned)) { - raw_spin_unlock_irqrestore_rcu_node(rnp, flags); - return; - } - /* Hold onto the leaf lock to make others see warned==1. */ - - if (rnp_root != rnp) - raw_spin_lock_rcu_node(rnp_root); /* irqs already disabled. */ - j = jiffies; - if (rcu_gp_in_progress() || - ULONG_CMP_GE(rnp_root->gp_seq, rnp_root->gp_seq_needed) || - time_before(j, rcu_state.gp_req_activity + gpssdelay) || - time_before(j, rcu_state.gp_activity + gpssdelay) || - atomic_xchg(&warned, 1)) { - raw_spin_unlock_rcu_node(rnp_root); /* irqs remain disabled. */ - raw_spin_unlock_irqrestore_rcu_node(rnp, flags); - return; - } - WARN_ON(1); - if (rnp_root != rnp) - raw_spin_unlock_rcu_node(rnp_root); - raw_spin_unlock_irqrestore_rcu_node(rnp, flags); - show_rcu_gp_kthreads(); -} - -/* - * Do a forward-progress check for rcutorture. This is normally invoked - * due to an OOM event. The argument "j" gives the time period during - * which rcutorture would like progress to have been made. - */ -void rcu_fwd_progress_check(unsigned long j) -{ - unsigned long cbs; - int cpu; - unsigned long max_cbs = 0; - int max_cpu = -1; - struct rcu_data *rdp; - - if (rcu_gp_in_progress()) { - pr_info("%s: GP age %lu jiffies\n", - __func__, jiffies - rcu_state.gp_start); - show_rcu_gp_kthreads(); - } else { - pr_info("%s: Last GP end %lu jiffies ago\n", - __func__, jiffies - rcu_state.gp_end); - preempt_disable(); - rdp = this_cpu_ptr(&rcu_data); - rcu_check_gp_start_stall(rdp->mynode, rdp, j); - preempt_enable(); - } - for_each_possible_cpu(cpu) { - cbs = rcu_get_n_cbs_cpu(cpu); - if (!cbs) - continue; - if (max_cpu < 0) - pr_info("%s: callbacks", __func__); - pr_cont(" %d: %lu", cpu, cbs); - if (cbs <= max_cbs) - continue; - max_cbs = cbs; - max_cpu = cpu; - } - if (max_cpu >= 0) - pr_cont("\n"); -} -EXPORT_SYMBOL_GPL(rcu_fwd_progress_check); - /* Perform RCU core processing work for the current CPU. */ static __latent_entropy void rcu_core(struct softirq_action *unused) { @@ -3559,13 +3081,11 @@ static int rcu_pm_notify(struct notifier_block *self, switch (action) { case PM_HIBERNATION_PREPARE: case PM_SUSPEND_PREPARE: - if (nr_cpu_ids <= 256) /* Expediting bad for large systems. */ - rcu_expedite_gp(); + rcu_expedite_gp(); break; case PM_POST_HIBERNATION: case PM_POST_SUSPEND: - if (nr_cpu_ids <= 256) /* Expediting bad for large systems. */ - rcu_unexpedite_gp(); + rcu_unexpedite_gp(); break; default: break; @@ -3742,8 +3262,7 @@ static void __init rcu_init_geometry(void) jiffies_till_first_fqs = d; if (jiffies_till_next_fqs == ULONG_MAX) jiffies_till_next_fqs = d; - if (jiffies_till_sched_qs == ULONG_MAX) - adjust_jiffies_till_sched_qs(); + adjust_jiffies_till_sched_qs(); /* If the compile-time values are accurate, just leave. */ if (rcu_fanout_leaf == RCU_FANOUT_LEAF && @@ -3858,5 +3377,6 @@ void __init rcu_init(void) srcu_init(); } +#include "tree_stall.h" #include "tree_exp.h" #include "tree_plugin.h" |