diff options
Diffstat (limited to 'kernel/rcu/tree.c')
| -rw-r--r-- | kernel/rcu/tree.c | 771 |
1 files changed, 179 insertions, 592 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 9a535a8..5d80925 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -102,6 +102,8 @@ struct rcu_state sname##_state = { \ .barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \ .name = RCU_STATE_NAME(sname), \ .abbr = sabbr, \ + .exp_mutex = __MUTEX_INITIALIZER(sname##_state.exp_mutex), \ + .exp_wake_mutex = __MUTEX_INITIALIZER(sname##_state.exp_wake_mutex), \ } RCU_STATE_INITIALIZER(rcu_sched, 's', call_rcu_sched); @@ -123,12 +125,14 @@ int rcu_num_lvls __read_mostly = RCU_NUM_LVLS; /* Number of rcu_nodes at specified level. */ static 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; /* * The rcu_scheduler_active variable transitions from zero to one just * before the first task is spawned. So when this variable is zero, RCU * can assume that there is but one task, allowing RCU to (for example) - * optimize synchronize_sched() to a simple barrier(). When this variable + * optimize synchronize_rcu() to a simple barrier(). When this variable * is one, RCU must actually do all the hard work required to detect real * grace periods. This variable is also used to suppress boot-time false * positives from lockdep-RCU error checking. @@ -157,6 +161,7 @@ static void invoke_rcu_core(void); static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp); static void rcu_report_exp_rdp(struct rcu_state *rsp, struct rcu_data *rdp, bool wake); +static void sync_sched_exp_online_cleanup(int cpu); /* rcuc/rcub kthread realtime priority */ #ifdef CONFIG_RCU_KTHREAD_PRIO @@ -370,6 +375,21 @@ void rcu_all_qs(void) rcu_momentary_dyntick_idle(); local_irq_restore(flags); } + if (unlikely(raw_cpu_read(rcu_sched_data.cpu_no_qs.b.exp))) { + /* + * Yes, we just checked a per-CPU variable with preemption + * enabled, so we might be migrated to some other CPU at + * this point. That is OK because in that case, the + * migration will supply the needed quiescent state. + * We might end up needlessly disabling preemption and + * invoking rcu_sched_qs() on the destination CPU, but + * the probability and cost are both quite low, so this + * should not be a problem in practice. + */ + preempt_disable(); + rcu_sched_qs(); + preempt_enable(); + } this_cpu_inc(rcu_qs_ctr); barrier(); /* Avoid RCU read-side critical sections leaking up. */ } @@ -385,9 +405,11 @@ module_param(qlowmark, long, 0444); static ulong jiffies_till_first_fqs = ULONG_MAX; static ulong jiffies_till_next_fqs = ULONG_MAX; +static bool rcu_kick_kthreads; module_param(jiffies_till_first_fqs, ulong, 0644); module_param(jiffies_till_next_fqs, ulong, 0644); +module_param(rcu_kick_kthreads, bool, 0644); /* * How long the grace period must be before we start recruiting @@ -460,6 +482,28 @@ unsigned long rcu_batches_completed_bh(void) EXPORT_SYMBOL_GPL(rcu_batches_completed_bh); /* + * Return the number of RCU expedited batches completed thus far for + * debug & stats. Odd numbers mean that a batch is in progress, even + * numbers mean idle. The value returned will thus be roughly double + * the cumulative batches since boot. + */ +unsigned long rcu_exp_batches_completed(void) +{ + return rcu_state_p->expedited_sequence; +} +EXPORT_SYMBOL_GPL(rcu_exp_batches_completed); + +/* + * Return the number of RCU-sched expedited batches completed thus far + * for debug & stats. Similar to rcu_exp_batches_completed(). + */ +unsigned long rcu_exp_batches_completed_sched(void) +{ + return rcu_sched_state.expedited_sequence; +} +EXPORT_SYMBOL_GPL(rcu_exp_batches_completed_sched); + +/* * Force a quiescent state. */ void rcu_force_quiescent_state(void) @@ -637,7 +681,7 @@ static void rcu_eqs_enter_common(long long oldval, bool user) idle_task(smp_processor_id()); trace_rcu_dyntick(TPS("Error on entry: not idle task"), oldval, 0); - ftrace_dump(DUMP_ORIG); + rcu_ftrace_dump(DUMP_ORIG); WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s", current->pid, current->comm, idle->pid, idle->comm); /* must be idle task! */ @@ -799,7 +843,7 @@ static void rcu_eqs_exit_common(long long oldval, int user) trace_rcu_dyntick(TPS("Error on exit: not idle task"), oldval, rdtp->dynticks_nesting); - ftrace_dump(DUMP_ORIG); + rcu_ftrace_dump(DUMP_ORIG); WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s", current->pid, current->comm, idle->pid, idle->comm); /* must be idle task! */ @@ -1029,11 +1073,11 @@ EXPORT_SYMBOL_GPL(rcu_is_watching); * offline to continue to use RCU for one jiffy after marking itself * offline in the cpu_online_mask. This leniency is necessary given the * non-atomic nature of the online and offline processing, for example, - * the fact that a CPU enters the scheduler after completing the CPU_DYING - * notifiers. + * the fact that a CPU enters the scheduler after completing the teardown + * of the CPU. * - * This is also why RCU internally marks CPUs online during the - * CPU_UP_PREPARE phase and offline during the CPU_DEAD phase. + * This is also why RCU internally marks CPUs online during in the + * preparation phase and offline after the CPU has been taken down. * * Disable checking if in an NMI handler because we cannot safely report * errors from NMI handlers anyway. @@ -1224,8 +1268,10 @@ static void rcu_check_gp_kthread_starvation(struct rcu_state *rsp) rsp->gp_flags, gp_state_getname(rsp->gp_state), rsp->gp_state, rsp->gp_kthread ? rsp->gp_kthread->state : ~0); - if (rsp->gp_kthread) + if (rsp->gp_kthread) { sched_show_task(rsp->gp_kthread); + wake_up_process(rsp->gp_kthread); + } } } @@ -1241,14 +1287,39 @@ static void rcu_dump_cpu_stacks(struct rcu_state *rsp) rcu_for_each_leaf_node(rsp, rnp) { raw_spin_lock_irqsave_rcu_node(rnp, flags); if (rnp->qsmask != 0) { - for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++) - if (rnp->qsmask & (1UL << cpu)) - dump_cpu_task(rnp->grplo + cpu); + for_each_leaf_node_possible_cpu(rnp, cpu) + if (rnp->qsmask & leaf_node_cpu_bit(rnp, 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(struct rcu_state *rsp) +{ + unsigned long j; + + if (!rcu_kick_kthreads) + return; + j = READ_ONCE(rsp->jiffies_kick_kthreads); + if (time_after(jiffies, j) && rsp->gp_kthread) { + WARN_ONCE(1, "Kicking %s grace-period kthread\n", rsp->name); + rcu_ftrace_dump(DUMP_ALL); + wake_up_process(rsp->gp_kthread); + WRITE_ONCE(rsp->jiffies_kick_kthreads, j + HZ); + } +} + +static inline void panic_on_rcu_stall(void) +{ + if (sysctl_panic_on_rcu_stall) + panic("RCU Stall\n"); +} + static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gpnum) { int cpu; @@ -1260,6 +1331,11 @@ static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gpnum) struct rcu_node *rnp = rcu_get_root(rsp); long totqlen = 0; + /* Kick and suppress, if so configured. */ + rcu_stall_kick_kthreads(rsp); + if (rcu_cpu_stall_suppress) + return; + /* Only let one CPU complain about others per time interval. */ raw_spin_lock_irqsave_rcu_node(rnp, flags); @@ -1284,10 +1360,9 @@ static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gpnum) raw_spin_lock_irqsave_rcu_node(rnp, flags); ndetected += rcu_print_task_stall(rnp); if (rnp->qsmask != 0) { - for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++) - if (rnp->qsmask & (1UL << cpu)) { - print_cpu_stall_info(rsp, - rnp->grplo + cpu); + for_each_leaf_node_possible_cpu(rnp, cpu) + if (rnp->qsmask & leaf_node_cpu_bit(rnp, cpu)) { + print_cpu_stall_info(rsp, cpu); ndetected++; } } @@ -1323,6 +1398,8 @@ static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gpnum) rcu_check_gp_kthread_starvation(rsp); + panic_on_rcu_stall(); + force_quiescent_state(rsp); /* Kick them all. */ } @@ -1333,6 +1410,11 @@ static void print_cpu_stall(struct rcu_state *rsp) struct rcu_node *rnp = rcu_get_root(rsp); long totqlen = 0; + /* Kick and suppress, if so configured. */ + rcu_stall_kick_kthreads(rsp); + if (rcu_cpu_stall_suppress) + return; + /* * OK, time to rat on ourselves... * See Documentation/RCU/stallwarn.txt for info on how to debug @@ -1358,6 +1440,8 @@ static void print_cpu_stall(struct rcu_state *rsp) 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. * @@ -1377,8 +1461,10 @@ static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) unsigned long js; struct rcu_node *rnp; - if (rcu_cpu_stall_suppress || !rcu_gp_in_progress(rsp)) + if ((rcu_cpu_stall_suppress && !rcu_kick_kthreads) || + !rcu_gp_in_progress(rsp)) return; + rcu_stall_kick_kthreads(rsp); j = jiffies; /* @@ -1915,8 +2001,7 @@ static bool rcu_gp_init(struct rcu_state *rsp) * 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. + * leaf node has been initialized. * * The grace period cannot complete until the initialization * process finishes, because this kthread handles both. @@ -2117,8 +2202,11 @@ static int __noreturn rcu_gp_kthread(void *arg) } ret = 0; for (;;) { - if (!ret) + if (!ret) { rsp->jiffies_force_qs = jiffies + j; + WRITE_ONCE(rsp->jiffies_kick_kthreads, + jiffies + 3 * j); + } trace_rcu_grace_period(rsp->name, READ_ONCE(rsp->gpnum), TPS("fqswait")); @@ -2144,6 +2232,15 @@ static int __noreturn rcu_gp_kthread(void *arg) TPS("fqsend")); cond_resched_rcu_qs(); WRITE_ONCE(rsp->gp_activity, jiffies); + ret = 0; /* Force full wait till next FQS. */ + j = jiffies_till_next_fqs; + if (j > HZ) { + j = HZ; + jiffies_till_next_fqs = HZ; + } else if (j < 1) { + j = 1; + jiffies_till_next_fqs = 1; + } } else { /* Deal with stray signal. */ cond_resched_rcu_qs(); @@ -2152,14 +2249,12 @@ static int __noreturn rcu_gp_kthread(void *arg) trace_rcu_grace_period(rsp->name, READ_ONCE(rsp->gpnum), TPS("fqswaitsig")); - } - j = jiffies_till_next_fqs; - if (j > HZ) { - j = HZ; - jiffies_till_next_fqs = HZ; - } else if (j < 1) { - j = 1; - jiffies_till_next_fqs = 1; + ret = 1; /* Keep old FQS timing. */ + j = jiffies; + if (time_after(jiffies, rsp->jiffies_force_qs)) + j = 1; + else + j = rsp->jiffies_force_qs - j; } } @@ -2788,7 +2883,6 @@ static void force_qs_rnp(struct rcu_state *rsp, unsigned long *maxj), bool *isidle, unsigned long *maxj) { - unsigned long bit; int cpu; unsigned long flags; unsigned long mask; @@ -2823,9 +2917,8 @@ static void force_qs_rnp(struct rcu_state *rsp, continue; } } - cpu = rnp->grplo; - bit = 1; - for (; cpu <= rnp->grphi; cpu++, bit <<= 1) { + for_each_leaf_node_possible_cpu(rnp, cpu) { + unsigned long bit = leaf_node_cpu_bit(rnp, cpu); if ((rnp->qsmask & bit) != 0) { if (f(per_cpu_ptr(rsp->rda, cpu), isidle, maxj)) mask |= bit; @@ -3364,508 +3457,6 @@ static bool rcu_seq_done(unsigned long *sp, unsigned long s) return ULONG_CMP_GE(READ_ONCE(*sp), s); } -/* Wrapper functions for expedited grace periods. */ -static void rcu_exp_gp_seq_start(struct rcu_state *rsp) -{ - rcu_seq_start(&rsp->expedited_sequence); -} -static void rcu_exp_gp_seq_end(struct rcu_state *rsp) -{ - rcu_seq_end(&rsp->expedited_sequence); - smp_mb(); /* Ensure that consecutive grace periods serialize. */ -} -static unsigned long rcu_exp_gp_seq_snap(struct rcu_state *rsp) -{ - smp_mb(); /* Caller's modifications seen first by other CPUs. */ - return rcu_seq_snap(&rsp->expedited_sequence); -} -static bool rcu_exp_gp_seq_done(struct rcu_state *rsp, unsigned long s) -{ - return rcu_seq_done(&rsp->expedited_sequence, s); -} - -/* - * Reset the ->expmaskinit values in the rcu_node tree to reflect any - * recent CPU-online activity. Note that these masks are not cleared - * when CPUs go offline, so they reflect the union of all CPUs that have - * ever been online. This means that this function normally takes its - * no-work-to-do fastpath. - */ -static void sync_exp_reset_tree_hotplug(struct rcu_state *rsp) -{ - bool done; - unsigned long flags; - unsigned long mask; - unsigned long oldmask; - int ncpus = READ_ONCE(rsp->ncpus); - struct rcu_node *rnp; - struct rcu_node *rnp_up; - - /* If no new CPUs onlined since last time, nothing to do. */ - if (likely(ncpus == rsp->ncpus_snap)) - return; - rsp->ncpus_snap = ncpus; - - /* - * Each pass through the following loop propagates newly onlined - * CPUs for the current rcu_node structure up the rcu_node tree. - */ - rcu_for_each_leaf_node(rsp, rnp) { - raw_spin_lock_irqsave_rcu_node(rnp, flags); - if (rnp->expmaskinit == rnp->expmaskinitnext) { - raw_spin_unlock_irqrestore_rcu_node(rnp, flags); - continue; /* No new CPUs, nothing to do. */ - } - - /* Update this node's mask, track old value for propagation. */ - oldmask = rnp->expmaskinit; - rnp->expmaskinit = rnp->expmaskinitnext; - raw_spin_unlock_irqrestore_rcu_node(rnp, flags); - - /* If was already nonzero, nothing to propagate. */ - if (oldmask) - continue; - - /* Propagate the new CPU up the tree. */ - mask = rnp->grpmask; - rnp_up = rnp->parent; - done = false; - while (rnp_up) { - raw_spin_lock_irqsave_rcu_node(rnp_up, flags); - if (rnp_up->expmaskinit) - done = true; - rnp_up->expmaskinit |= mask; - raw_spin_unlock_irqrestore_rcu_node(rnp_up, flags); - if (done) - break; - mask = rnp_up->grpmask; - rnp_up = rnp_up->parent; - } - } -} - -/* - * Reset the ->expmask values in the rcu_node tree in preparation for - * a new expedited grace period. - */ -static void __maybe_unused sync_exp_reset_tree(struct rcu_state *rsp) -{ - unsigned long flags; - struct rcu_node *rnp; - - sync_exp_reset_tree_hotplug(rsp); - rcu_for_each_node_breadth_first(rsp, rnp) { - raw_spin_lock_irqsave_rcu_node(rnp, flags); - WARN_ON_ONCE(rnp->expmask); - rnp->expmask = rnp->expmaskinit; - raw_spin_unlock_irqrestore_rcu_node(rnp, flags); - } -} - -/* - * Return non-zero if there is no RCU expedited grace period in progress - * for the specified rcu_node structure, in other words, if all CPUs and - * tasks covered by the specified rcu_node structure have done their bit - * for the current expedited grace period. Works only for preemptible - * RCU -- other RCU implementation use other means. - * - * Caller must hold the root rcu_node's exp_funnel_mutex. - */ -static int sync_rcu_preempt_exp_done(struct rcu_node *rnp) -{ - return rnp->exp_tasks == NULL && - READ_ONCE(rnp->expmask) == 0; -} - -/* - * 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 - * which the task was queued or to one of that rcu_node structure's ancestors, - * recursively up the tree. (Calm down, calm down, we do the recursion - * iteratively!) - * - * Caller must hold the root rcu_node's exp_funnel_mutex and 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) - __releases(rnp->lock) -{ - unsigned long mask; - - for (;;) { - if (!sync_rcu_preempt_exp_done(rnp)) { - if (!rnp->expmask) - rcu_initiate_boost(rnp, flags); - else - raw_spin_unlock_irqrestore_rcu_node(rnp, flags); - break; - } - if (rnp->parent == NULL) { - raw_spin_unlock_irqrestore_rcu_node(rnp, flags); - if (wake) { - smp_mb(); /* EGP done before wake_up(). */ - swake_up(&rsp->expedited_wq); - } - break; - } - mask = rnp->grpmask; - raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled */ - rnp = rnp->parent; - raw_spin_lock_rcu_node(rnp); /* irqs already disabled */ - WARN_ON_ONCE(!(rnp->expmask & mask)); - rnp->expmask &= ~mask; - } -} - -/* - * Report expedited quiescent state for specified node. This is a - * lock-acquisition wrapper function for __rcu_report_exp_rnp(). - * - * Caller must hold the root rcu_node's exp_funnel_mutex. - */ -static void __maybe_unused rcu_report_exp_rnp(struct rcu_state *rsp, - struct rcu_node *rnp, bool wake) -{ - unsigned long flags; - - raw_spin_lock_irqsave_rcu_node(rnp, flags); - __rcu_report_exp_rnp(rsp, rnp, wake, flags); -} - -/* - * Report expedited quiescent state for multiple CPUs, all covered by the - * specified leaf rcu_node structure. Caller must hold the root - * rcu_node's exp_funnel_mutex. - */ -static void rcu_report_exp_cpu_mult(struct rcu_state *rsp, struct rcu_node *rnp, - unsigned long mask, bool wake) -{ - unsigned long flags; - - raw_spin_lock_irqsave_rcu_node(rnp, flags); - if (!(rnp->expmask & mask)) { - raw_spin_unlock_irqrestore_rcu_node(rnp, flags); - return; - } - rnp->expmask &= ~mask; - __rcu_report_exp_rnp(rsp, rnp, wake, flags); /* Releases rnp->lock. */ -} - -/* - * Report expedited quiescent state for specified rcu_data (CPU). - * Caller must hold the root rcu_node's exp_funnel_mutex. - */ -static void rcu_report_exp_rdp(struct rcu_state *rsp, struct rcu_data *rdp, - bool wake) -{ - rcu_report_exp_cpu_mult(rsp, rdp->mynode, rdp->grpmask, wake); -} - -/* Common code for synchronize_{rcu,sched}_expedited() work-done checking. */ -static bool sync_exp_work_done(struct rcu_state *rsp, struct rcu_node *rnp, - struct rcu_data *rdp, - atomic_long_t *stat, unsigned long s) -{ - if (rcu_exp_gp_seq_done(rsp, s)) { - if (rnp) - mutex_unlock(&rnp->exp_funnel_mutex); - else if (rdp) - mutex_unlock(&rdp->exp_funnel_mutex); - /* Ensure test happens before caller kfree(). */ - smp_mb__before_atomic(); /* ^^^ */ - atomic_long_inc(stat); - return true; - } - return false; -} - -/* - * Funnel-lock acquisition for expedited grace periods. Returns a - * pointer to the root rcu_node structure, or NULL if some other - * task did the expedited grace period for us. - */ -static struct rcu_node *exp_funnel_lock(struct rcu_state *rsp, unsigned long s) -{ - struct rcu_data *rdp = per_cpu_ptr(rsp->rda, raw_smp_processor_id()); - struct rcu_node *rnp0; - struct rcu_node *rnp1 = NULL; - - /* - * First try directly acquiring the root lock in order to reduce - * latency in the common case where expedited grace periods are - * rare. We check mutex_is_locked() to avoid pathological levels of - * memory contention on ->exp_funnel_mutex in the heavy-load case. - */ - rnp0 = rcu_get_root(rsp); - if (!mutex_is_locked(&rnp0->exp_funnel_mutex)) { - if (mutex_trylock(&rnp0->exp_funnel_mutex)) { - if (sync_exp_work_done(rsp, rnp0, NULL, - &rdp->expedited_workdone0, s)) - return NULL; - return rnp0; - } - } - - /* - * Each pass through the following loop works its way - * up the rcu_node tree, returning if others have done the - * work or otherwise falls through holding the root rnp's - * ->exp_funnel_mutex. The mapping from CPU to rcu_node structure - * can be inexact, as it is just promoting locality and is not - * strictly needed for correctness. - */ - if (sync_exp_work_done(rsp, NULL, NULL, &rdp->expedited_workdone1, s)) - return NULL; - mutex_lock(&rdp->exp_funnel_mutex); - rnp0 = rdp->mynode; - for (; rnp0 != NULL; rnp0 = rnp0->parent) { - if (sync_exp_work_done(rsp, rnp1, rdp, - &rdp->expedited_workdone2, s)) - return NULL; - mutex_lock(&rnp0->exp_funnel_mutex); - if (rnp1) - mutex_unlock(&rnp1->exp_funnel_mutex); - else - mutex_unlock(&rdp->exp_funnel_mutex); - rnp1 = rnp0; - } - if (sync_exp_work_done(rsp, rnp1, rdp, - &rdp->expedited_workdone3, s)) - return NULL; - return rnp1; -} - -/* Invoked on each online non-idle CPU for expedited quiescent state. */ -static void sync_sched_exp_handler(void *data) -{ - struct rcu_data *rdp; - struct rcu_node *rnp; - struct rcu_state *rsp = data; - - rdp = this_cpu_ptr(rsp->rda); - rnp = rdp->mynode; - if (!(READ_ONCE(rnp->expmask) & rdp->grpmask) || - __this_cpu_read(rcu_sched_data.cpu_no_qs.b.exp)) - return; - __this_cpu_write(rcu_sched_data.cpu_no_qs.b.exp, true); - resched_cpu(smp_processor_id()); -} - -/* Send IPI for expedited cleanup if needed at end of CPU-hotplug operation. */ -static void sync_sched_exp_online_cleanup(int cpu) -{ - struct rcu_data *rdp; - int ret; - struct rcu_node *rnp; - struct rcu_state *rsp = &rcu_sched_state; - - rdp = per_cpu_ptr(rsp->rda, cpu); - rnp = rdp->mynode; - if (!(READ_ONCE(rnp->expmask) & rdp->grpmask)) - return; - ret = smp_call_function_single(cpu, sync_sched_exp_handler, rsp, 0); - WARN_ON_ONCE(ret); -} - -/* - * 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) -{ - int cpu; - unsigned long flags; - unsigned long mask; - unsigned long mask_ofl_test; - unsigned long mask_ofl_ipi; - int ret; - struct rcu_node *rnp; - - sync_exp_reset_tree(rsp); - rcu_for_each_leaf_node(rsp, rnp) { - raw_spin_lock_irqsave_rcu_node(rnp, flags); - - /* Each pass checks a CPU for identity, offline, and idle. */ - mask_ofl_test = 0; - for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++) { - struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); - struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); - - if (raw_smp_processor_id() == cpu || - !(atomic_add_return(0, &rdtp->dynticks) & 0x1)) - mask_ofl_test |= rdp->grpmask; - } - 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); - - /* IPI the remaining CPUs for expedited quiescent state. */ - mask = 1; - for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask <<= 1) { - if (!(mask_ofl_ipi & mask)) - continue; -retry_ipi: - ret = smp_call_function_single(cpu, func, rsp, 0); - if (!ret) { - mask_ofl_ipi &= ~mask; - continue; - } - /* Failed, raced with offline. */ - raw_spin_lock_irqsave_rcu_node(rnp, flags); - if (cpu_online(cpu) && - (rnp->expmask & mask)) { - raw_spin_unlock_irqrestore_rcu_node(rnp, flags); - schedule_timeout_uninterruptible(1); - if (cpu_online(cpu) && - (rnp->expmask & mask)) - goto retry_ipi; - raw_spin_lock_irqsave_rcu_node(rnp, flags); - } - 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); - } -} - -static void synchronize_sched_expedited_wait(struct rcu_state *rsp) -{ - int cpu; - unsigned long jiffies_stall; - unsigned long jiffies_start; - unsigned long mask; - int ndetected; - struct rcu_node *rnp; - struct rcu_node *rnp_root = rcu_get_root(rsp); - int ret; - - jiffies_stall = rcu_jiffies_till_stall_check(); - jiffies_start = jiffies; - - for (;;) { - ret = swait_event_timeout( - rsp->expedited_wq, - sync_rcu_preempt_exp_done(rnp_root), - jiffies_stall); - if (ret > 0 || sync_rcu_preempt_exp_done(rnp_root)) - return; - if (ret < 0) { - /* Hit a signal, disable CPU stall warnings. */ - swait_event(rsp->expedited_wq, - sync_rcu_preempt_exp_done(rnp_root)); - return; - } - pr_err("INFO: %s detected expedited stalls on CPUs/tasks: {", - rsp->name); - ndetected = 0; - rcu_for_each_leaf_node(rsp, rnp) { - ndetected = rcu_print_task_exp_stall(rnp); - mask = 1; - for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask <<= 1) { - struct rcu_data *rdp; - - if (!(rnp->expmask & mask)) - continue; - ndetected++; - rdp = per_cpu_ptr(rsp->rda, cpu); - pr_cont(" %d-%c%c%c", cpu, - "O."[cpu_online(cpu)], - "o."[!!(rdp->grpmask & rnp->expmaskinit)], - "N."[!!(rdp->grpmask & rnp->expmaskinitnext)]); - } - mask <<= 1; - } - pr_cont(" } %lu jiffies s: %lu root: %#lx/%c\n", - jiffies - jiffies_start, rsp->expedited_sequence, - rnp_root->expmask, ".T"[!!rnp_root->exp_tasks]); - if (!ndetected) { - pr_err("blocking rcu_node structures:"); - rcu_for_each_node_breadth_first(rsp, rnp) { - if (rnp == rnp_root) - continue; /* printed unconditionally */ - if (sync_rcu_preempt_exp_done(rnp)) - continue; - pr_cont(" l=%u:%d-%d:%#lx/%c", - rnp->level, rnp->grplo, rnp->grphi, - rnp->expmask, - ".T"[!!rnp->exp_tasks]); - } - pr_cont("\n"); - } - rcu_for_each_leaf_node(rsp, rnp) { - mask = 1; - for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask <<= 1) { - if (!(rnp->expmask & mask)) - continue; - dump_cpu_task(cpu); - } - } - jiffies_stall = 3 * rcu_jiffies_till_stall_check() + 3; - } -} - -/** - * synchronize_sched_expedited - Brute-force RCU-sched grace period - * - * Wait for an RCU-sched grace period to elapse, but use a "big hammer" - * approach to force the grace period to end quickly. This consumes - * significant time on all CPUs and is unfriendly to real-time workloads, - * so is thus not recommended for any sort of common-case code. In fact, - * if you are using synchronize_sched_expedited() in a loop, please - * restructure your code to batch your updates, and then use a single - * synchronize_sched() instead. - * - * This implementation can be thought of as an application of sequence - * locking to expedited grace periods, but using the sequence counter to - * determine when someone else has already done the work instead of for - * retrying readers. - */ -void synchronize_sched_expedited(void) -{ - unsigned long s; - struct rcu_node *rnp; - struct rcu_state *rsp = &rcu_sched_state; - - /* If only one CPU, this is automatically a grace period. */ - if (rcu_blocking_is_gp()) - return; - - /* If expedited grace periods are prohibited, fall back to normal. */ - if (rcu_gp_is_normal()) { - wait_rcu_gp(call_rcu_sched); - return; - } - - /* Take a snapshot of the sequence number. */ - s = rcu_exp_gp_seq_snap(rsp); - - rnp = exp_funnel_lock(rsp, s); - if (rnp == NULL) - return; /* Someone else did our work for us. */ - - rcu_exp_gp_seq_start(rsp); - sync_rcu_exp_select_cpus(rsp, sync_sched_exp_handler); - synchronize_sched_expedited_wait(rsp); - - rcu_exp_gp_seq_end(rsp); - mutex_unlock(&rnp->exp_funnel_mutex); -} -EXPORT_SYMBOL_GPL(synchronize_sched_expedited); - /* * 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. @@ -4156,13 +3747,12 @@ rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) /* Set up local state, ensuring consistent view of global state. */ raw_spin_lock_irqsave_rcu_node(rnp, flags); - rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo); + rdp->grpmask = leaf_node_cpu_bit(rdp->mynode, cpu); rdp->dynticks = &per_cpu(rcu_dynticks, cpu); WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_EXIT_IDLE); WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1); rdp->cpu = cpu; rdp->rsp = rsp; - mutex_init(&rdp->exp_funnel_mutex); rcu_boot_init_nocb_percpu_data(rdp); raw_spin_unlock_irqrestore_rcu_node(rnp, flags); } @@ -4216,12 +3806,58 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp) raw_spin_unlock_irqrestore_rcu_node(rnp, flags); } -static void rcu_prepare_cpu(int cpu) +int rcutree_prepare_cpu(unsigned int cpu) { struct rcu_state *rsp; for_each_rcu_flavor(rsp) rcu_init_percpu_data(cpu, rsp); + + rcu_prepare_kthreads(cpu); + rcu_spawn_all_nocb_kthreads(cpu); + + return 0; +} + +static void rcutree_affinity_setting(unsigned int cpu, int outgoing) +{ + struct rcu_data *rdp = per_cpu_ptr(rcu_state_p->rda, cpu); + + rcu_boost_kthread_setaffinity(rdp->mynode, outgoing); +} + +int rcutree_online_cpu(unsigned int cpu) +{ + sync_sched_exp_online_cleanup(cpu); + rcutree_affinity_setting(cpu, -1); + return 0; +} + +int rcutree_offline_cpu(unsigned int cpu) +{ + rcutree_affinity_setting(cpu, cpu); + return 0; +} + + +int rcutree_dying_cpu(unsigned int cpu) +{ + struct rcu_state *rsp; + + for_each_rcu_flavor(rsp) + rcu_cleanup_dying_cpu(rsp); + return 0; +} + +int rcutree_dead_cpu(unsigned int cpu) +{ + struct rcu_state *rsp; + + for_each_rcu_flavor(rsp) { + rcu_cleanup_dead_cpu(cpu, rsp); + do_nocb_deferred_wakeup(per_cpu_ptr(rsp->rda, cpu)); + } + return 0; } #ifdef CONFIG_HOTPLUG_CPU @@ -4240,9 +3876,6 @@ static void rcu_cleanup_dying_idle_cpu(int cpu, struct rcu_state *rsp) struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */ - if (!IS_ENABLED(CONFIG_HOTPLUG_CPU)) - return; - /* Remove outgoing CPU from mask in the leaf rcu_node structure. */ mask = rdp->grpmask; raw_spin_lock_irqsave_rcu_node(rnp, flags); /* Enforce GP memory-order guarantee. */ @@ -4264,52 +3897,6 @@ void rcu_report_dead(unsigned int cpu) } #endif -/* - * Handle CPU online/offline notification events. - */ -int rcu_cpu_notify(struct notifier_block *self, - unsigned long action, void *hcpu) -{ - long cpu = (long)hcpu; - struct rcu_data *rdp = per_cpu_ptr(rcu_state_p->rda, cpu); - struct rcu_node *rnp = rdp->mynode; - struct rcu_state *rsp; - - switch (action) { - case CPU_UP_PREPARE: - case CPU_UP_PREPARE_FROZEN: - rcu_prepare_cpu(cpu); - rcu_prepare_kthreads(cpu); - rcu_spawn_all_nocb_kthreads(cpu); - break; - case CPU_ONLINE: - case CPU_DOWN_FAILED: - sync_sched_exp_online_cleanup(cpu); - rcu_boost_kthread_setaffinity(rnp, -1); - break; - case CPU_DOWN_PREPARE: - rcu_boost_kthread_setaffinity(rnp, cpu); - break; - case CPU_DYING: - case CPU_DYING_FROZEN: - for_each_rcu_flavor(rsp) - rcu_cleanup_dying_cpu(rsp); - break; - case CPU_DEAD: - case CPU_DEAD_FROZEN: - case CPU_UP_CANCELED: - case CPU_UP_CANCELED_FROZEN: - for_each_rcu_flavor(rsp) { - rcu_cleanup_dead_cpu(cpu, rsp); - do_nocb_deferred_wakeup(per_cpu_ptr(rsp->rda, cpu)); - } - break; - default: - break; - } - return NOTIFY_OK; -} - static int rcu_pm_notify(struct notifier_block *self, unsigned long action, void *hcpu) { @@ -4420,10 +4007,8 @@ static void __init rcu_init_one(struct rcu_state *rsp) { static const char * const buf[] = RCU_NODE_NAME_INIT; static const char * const fqs[] = RCU_FQS_NAME_INIT; - static const char * const exp[] = RCU_EXP_NAME_INIT; static struct lock_class_key rcu_node_class[RCU_NUM_LVLS]; static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS]; - static struct lock_class_key rcu_exp_class[RCU_NUM_LVLS]; static u8 fl_mask = 0x1; int levelcnt[RCU_NUM_LVLS]; /* # nodes in each level. */ @@ -4482,9 +4067,11 @@ static void __init rcu_init_one(struct rcu_state *rsp) rnp->level = i; INIT_LIST_HEAD(&rnp->blkd_tasks); rcu_init_one_nocb(rnp); - mutex_init(&rnp->exp_funnel_mutex); - lockdep_set_class_and_name(&rnp->exp_funnel_mutex, - &rcu_exp_class[i], exp[i]); + init_waitqueue_head(&rnp->exp_wq[0]); + init_waitqueue_head(&rnp->exp_wq[1]); + init_waitqueue_head(&rnp->exp_wq[2]); + init_waitqueue_head(&rnp->exp_wq[3]); + spin_lock_init(&rnp->exp_lock); } } @@ -4621,10 +4208,10 @@ void __init rcu_init(void) * this is called early in boot, before either interrupts * or the scheduler are operational. */ - cpu_notifier(rcu_cpu_notify, 0); pm_notifier(rcu_pm_notify, 0); for_each_online_cpu(cpu) - rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu); + rcutree_prepare_cpu(cpu); } +#include "tree_exp.h" #include "tree_plugin.h" |
