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-rw-r--r--kernel/rcu/tree.c545
1 files changed, 2 insertions, 543 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 4aefeafb9a95..c844b6142a86 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -159,6 +159,7 @@ 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
@@ -3447,549 +3448,6 @@ 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)
-{
- unsigned long s;
-
- smp_mb(); /* Caller's modifications seen first by other CPUs. */
- s = rcu_seq_snap(&rsp->expedited_sequence);
- trace_rcu_exp_grace_period(rsp->name, s, TPS("snap"));
- return s;
-}
-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 rcu_state's exp_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 rcu_state's exp_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 rcu_state's exp_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 rcu_state's
- * exp_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).
- */
-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, atomic_long_t *stat,
- 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;
-}
-
-/*
- * Funnel-lock acquisition for expedited grace periods. Returns true
- * if some other task completed an expedited grace period that this task
- * can piggy-back on, and with no mutex held. Otherwise, returns false
- * with the mutex held, indicating that the caller must actually do the
- * expedited grace period.
- */
-static bool 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 *rnp = rdp->mynode;
- struct rcu_node *rnp_root = rcu_get_root(rsp);
-
- /* Low-contention fastpath. */
- if (ULONG_CMP_LT(READ_ONCE(rnp->exp_seq_rq), s) &&
- (rnp == rnp_root ||
- ULONG_CMP_LT(READ_ONCE(rnp_root->exp_seq_rq), s)) &&
- !mutex_is_locked(&rsp->exp_mutex) &&
- mutex_trylock(&rsp->exp_mutex))
- goto fastpath;
-
- /*
- * 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 to acquire rsp->exp_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.
- */
- for (; rnp != NULL; rnp = rnp->parent) {
- if (sync_exp_work_done(rsp, &rdp->exp_workdone1, s))
- return true;
-
- /* Work not done, either wait here or go up. */
- spin_lock(&rnp->exp_lock);
- if (ULONG_CMP_GE(rnp->exp_seq_rq, s)) {
-
- /* Someone else doing GP, so wait for them. */
- spin_unlock(&rnp->exp_lock);
- trace_rcu_exp_funnel_lock(rsp->name, rnp->level,
- rnp->grplo, rnp->grphi,
- TPS("wait"));
- wait_event(rnp->exp_wq[(s >> 1) & 0x3],
- sync_exp_work_done(rsp,
- &rdp->exp_workdone2, s));
- return true;
- }
- rnp->exp_seq_rq = s; /* Followers can wait on us. */
- spin_unlock(&rnp->exp_lock);
- trace_rcu_exp_funnel_lock(rsp->name, rnp->level, rnp->grplo,
- rnp->grphi, TPS("nxtlvl"));
- }
- mutex_lock(&rsp->exp_mutex);
-fastpath:
- if (sync_exp_work_done(rsp, &rdp->exp_workdone3, s)) {
- mutex_unlock(&rsp->exp_mutex);
- return true;
- }
- rcu_exp_gp_seq_start(rsp);
- trace_rcu_exp_grace_period(rsp->name, s, TPS("start"));
- return false;
-}
-
-/* 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;
- if (rcu_is_cpu_rrupt_from_idle()) {
- rcu_report_exp_rdp(&rcu_sched_state,
- this_cpu_ptr(&rcu_sched_data), true);
- 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;
- }
-}
-
-/*
- * Wait for the current expedited grace period to complete, and then
- * wake up everyone who piggybacked on the just-completed expedited
- * grace period. Also update all the ->exp_seq_rq counters as needed
- * in order to avoid counter-wrap problems.
- */
-static void rcu_exp_wait_wake(struct rcu_state *rsp, unsigned long s)
-{
- struct rcu_node *rnp;
-
- synchronize_sched_expedited_wait(rsp);
- rcu_exp_gp_seq_end(rsp);
- trace_rcu_exp_grace_period(rsp->name, s, TPS("end"));
-
- /*
- * Switch over to wakeup mode, allowing the next GP, but -only- the
- * next GP, to proceed.
- */
- mutex_lock(&rsp->exp_wake_mutex);
- mutex_unlock(&rsp->exp_mutex);
-
- rcu_for_each_node_breadth_first(rsp, rnp) {
- if (ULONG_CMP_LT(READ_ONCE(rnp->exp_seq_rq), s)) {
- spin_lock(&rnp->exp_lock);
- /* Recheck, avoid hang in case someone just arrived. */
- if (ULONG_CMP_LT(rnp->exp_seq_rq, s))
- rnp->exp_seq_rq = s;
- spin_unlock(&rnp->exp_lock);
- }
- wake_up_all(&rnp->exp_wq[(rsp->expedited_sequence >> 1) & 0x3]);
- }
- trace_rcu_exp_grace_period(rsp->name, s, TPS("endwake"));
- mutex_unlock(&rsp->exp_wake_mutex);
-}
-
-/**
- * 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_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);
- if (exp_funnel_lock(rsp, s))
- return; /* Someone else did our work for us. */
-
- /* Initialize the rcu_node tree in preparation for the wait. */
- sync_rcu_exp_select_cpus(rsp, sync_sched_exp_handler);
-
- /* Wait and clean up, including waking everyone. */
- rcu_exp_wait_wake(rsp, s);
-}
-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.
@@ -4747,4 +4205,5 @@ void __init rcu_init(void)
rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu);
}
+#include "tree_exp.h"
#include "tree_plugin.h"
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