static void invoke_rcu_core(void);
static void rcu_report_exp_rdp(struct rcu_data *rdp);
static void sync_sched_exp_online_cleanup(int cpu);
+static void check_cb_ovld_locked(struct rcu_data *rdp, struct rcu_node *rnp);
/* rcuc/rcub kthread realtime priority */
static int kthread_prio = IS_ENABLED(CONFIG_RCU_BOOST) ? 1 : 0;
static long qhimark = DEFAULT_RCU_QHIMARK;
#define DEFAULT_RCU_QLOMARK 100 /* Once only this many pending, use blimit. */
static long qlowmark = DEFAULT_RCU_QLOMARK;
+#define DEFAULT_RCU_QOVLD_MULT 2
+#define DEFAULT_RCU_QOVLD (DEFAULT_RCU_QOVLD_MULT * DEFAULT_RCU_QHIMARK)
+static long qovld = DEFAULT_RCU_QOVLD; /* If this many pending, hammer QS. */
+static long qovld_calc = -1; /* No pre-initialization lock acquisitions! */
module_param(blimit, long, 0444);
module_param(qhimark, long, 0444);
module_param(qlowmark, long, 0444);
+module_param(qovld, long, 0444);
static ulong jiffies_till_first_fqs = ULONG_MAX;
static ulong jiffies_till_next_fqs = ULONG_MAX;
rnhqp = &per_cpu(rcu_data.rcu_need_heavy_qs, rdp->cpu);
if (!READ_ONCE(*rnhqp) &&
(time_after(jiffies, rcu_state.gp_start + jtsq * 2) ||
- time_after(jiffies, rcu_state.jiffies_resched))) {
+ time_after(jiffies, rcu_state.jiffies_resched) ||
+ rcu_state.cbovld)) {
WRITE_ONCE(*rnhqp, true);
/* Store rcu_need_heavy_qs before rcu_urgent_qs. */
smp_store_release(ruqp, true);
* So hit them over the head with the resched_cpu() hammer!
*/
if (tick_nohz_full_cpu(rdp->cpu) &&
- time_after(jiffies,
- READ_ONCE(rdp->last_fqs_resched) + jtsq * 3)) {
+ (time_after(jiffies, READ_ONCE(rdp->last_fqs_resched) + jtsq * 3) ||
+ rcu_state.cbovld)) {
WRITE_ONCE(*ruqp, true);
resched_cpu(rdp->cpu);
WRITE_ONCE(rdp->last_fqs_resched, jiffies);
static bool __note_gp_changes(struct rcu_node *rnp, struct rcu_data *rdp)
{
bool ret = false;
- bool need_gp;
+ bool need_qs;
const bool offloaded = IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
rcu_segcblist_is_offloaded(&rdp->cblist);
unlikely(READ_ONCE(rdp->gpwrap))) {
if (!offloaded)
ret = rcu_advance_cbs(rnp, rdp); /* Advance CBs. */
+ rdp->core_needs_qs = false;
trace_rcu_grace_period(rcu_state.name, rdp->gp_seq, TPS("cpuend"));
} else {
if (!offloaded)
ret = rcu_accelerate_cbs(rnp, rdp); /* Recent CBs. */
+ if (rdp->core_needs_qs)
+ rdp->core_needs_qs = !!(rnp->qsmask & rdp->grpmask);
}
/* Now handle the beginnings of any new-to-this-CPU grace periods. */
* go looking for one.
*/
trace_rcu_grace_period(rcu_state.name, rnp->gp_seq, TPS("cpustart"));
- need_gp = !!(rnp->qsmask & rdp->grpmask);
- rdp->cpu_no_qs.b.norm = need_gp;
- rdp->core_needs_qs = need_gp;
+ need_qs = !!(rnp->qsmask & rdp->grpmask);
+ rdp->cpu_no_qs.b.norm = need_qs;
+ rdp->core_needs_qs = need_qs;
zero_cpu_stall_ticks(rdp);
}
rdp->gp_seq = rnp->gp_seq; /* Remember new grace-period state. */
*/
static void rcu_gp_cleanup(void)
{
- unsigned long gp_duration;
+ int cpu;
bool needgp = false;
+ unsigned long gp_duration;
unsigned long new_gp_seq;
bool offloaded;
struct rcu_data *rdp;
needgp = __note_gp_changes(rnp, rdp) || needgp;
/* smp_mb() provided by prior unlock-lock pair. */
needgp = rcu_future_gp_cleanup(rnp) || needgp;
+ // Reset overload indication for CPUs no longer overloaded
+ if (rcu_is_leaf_node(rnp))
+ for_each_leaf_node_cpu_mask(rnp, cpu, rnp->cbovldmask) {
+ rdp = per_cpu_ptr(&rcu_data, cpu);
+ check_cb_ovld_locked(rdp, rnp);
+ }
sq = rcu_nocb_gp_get(rnp);
raw_spin_unlock_irq_rcu_node(rnp);
rcu_nocb_gp_cleanup(sq);
return;
}
mask = rdp->grpmask;
+ if (rdp->cpu == smp_processor_id())
+ rdp->core_needs_qs = false;
if ((rnp->qsmask & mask) == 0) {
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
} else {
struct rcu_data *rdp;
struct rcu_node *rnp;
+ rcu_state.cbovld = rcu_state.cbovldnext;
+ rcu_state.cbovldnext = false;
rcu_for_each_leaf_node(rnp) {
cond_resched_tasks_rcu_qs();
mask = 0;
raw_spin_lock_irqsave_rcu_node(rnp, flags);
+ rcu_state.cbovldnext |= !!rnp->cbovldmask;
if (rnp->qsmask == 0) {
if (!IS_ENABLED(CONFIG_PREEMPT_RCU) ||
rcu_preempt_blocked_readers_cgp(rnp)) {
{
}
+/*
+ * Check and if necessary update the leaf rcu_node structure's
+ * ->cbovldmask bit corresponding to the current CPU based on that CPU's
+ * number of queued RCU callbacks. The caller must hold the leaf rcu_node
+ * structure's ->lock.
+ */
+static void check_cb_ovld_locked(struct rcu_data *rdp, struct rcu_node *rnp)
+{
+ raw_lockdep_assert_held_rcu_node(rnp);
+ if (qovld_calc <= 0)
+ return; // Early boot and wildcard value set.
+ if (rcu_segcblist_n_cbs(&rdp->cblist) >= qovld_calc)
+ WRITE_ONCE(rnp->cbovldmask, rnp->cbovldmask | rdp->grpmask);
+ else
+ WRITE_ONCE(rnp->cbovldmask, rnp->cbovldmask & ~rdp->grpmask);
+}
+
+/*
+ * Check and if necessary update the leaf rcu_node structure's
+ * ->cbovldmask bit corresponding to the current CPU based on that CPU's
+ * number of queued RCU callbacks. No locks need be held, but the
+ * caller must have disabled interrupts.
+ *
+ * Note that this function ignores the possibility that there are a lot
+ * of callbacks all of which have already seen the end of their respective
+ * grace periods. This omission is due to the need for no-CBs CPUs to
+ * be holding ->nocb_lock to do this check, which is too heavy for a
+ * common-case operation.
+ */
+static void check_cb_ovld(struct rcu_data *rdp)
+{
+ struct rcu_node *const rnp = rdp->mynode;
+
+ if (qovld_calc <= 0 ||
+ ((rcu_segcblist_n_cbs(&rdp->cblist) >= qovld_calc) ==
+ !!(READ_ONCE(rnp->cbovldmask) & rdp->grpmask)))
+ return; // Early boot wildcard value or already set correctly.
+ raw_spin_lock_rcu_node(rnp);
+ check_cb_ovld_locked(rdp, rnp);
+ raw_spin_unlock_rcu_node(rnp);
+}
+
/*
* Helper function for call_rcu() and friends. The cpu argument will
* normally be -1, indicating "currently running CPU". It may specify
rcu_segcblist_init(&rdp->cblist);
}
+ check_cb_ovld(rdp);
if (rcu_nocb_try_bypass(rdp, head, &was_alldone, flags))
return; // Enqueued onto ->nocb_bypass, so just leave.
/* If we get here, rcu_nocb_try_bypass() acquired ->nocb_lock. */
rcu_par_gp_wq = alloc_workqueue("rcu_par_gp", WQ_MEM_RECLAIM, 0);
WARN_ON(!rcu_par_gp_wq);
srcu_init();
+
+ /* Fill in default value for rcutree.qovld boot parameter. */
+ /* -After- the rcu_node ->lock fields are initialized! */
+ if (qovld < 0)
+ qovld_calc = DEFAULT_RCU_QOVLD_MULT * qhimark;
+ else
+ qovld_calc = qovld;
}
#include "tree_stall.h"
projects / linux-2.6-block.git / blobdiff