From 61598093bbdd283a7edc367d900f223070ead8d2 Mon Sep 17 00:00:00 2001
From: hc <hc@nodka.com>
Date: Fri, 10 May 2024 07:43:03 +0000
Subject: [PATCH] add ax88772C AX88772C_eeprom_tools
---
kernel/kernel/rcu/tree_exp.h | 725 ++++++++++++++++++++++++++++++-------------------------
1 files changed, 399 insertions(+), 326 deletions(-)
diff --git a/kernel/kernel/rcu/tree_exp.h b/kernel/kernel/rcu/tree_exp.h
index ac6d6fd..fad86be 100644
--- a/kernel/kernel/rcu/tree_exp.h
+++ b/kernel/kernel/rcu/tree_exp.h
@@ -1,63 +1,55 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
/*
* RCU expedited grace periods
*
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, you can access it online at
- * http://www.gnu.org/licenses/gpl-2.0.html.
- *
* Copyright IBM Corporation, 2016
*
- * Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+ * Authors: Paul E. McKenney <paulmck@linux.ibm.com>
*/
#include <linux/lockdep.h>
+static void rcu_exp_handler(void *unused);
+static int rcu_print_task_exp_stall(struct rcu_node *rnp);
+
/*
* Record the start of an expedited grace period.
*/
-static void rcu_exp_gp_seq_start(struct rcu_state *rsp)
+static void rcu_exp_gp_seq_start(void)
{
- rcu_seq_start(&rsp->expedited_sequence);
+ rcu_seq_start(&rcu_state.expedited_sequence);
}
/*
- * Return then value that expedited-grace-period counter will have
+ * Return the value that the expedited-grace-period counter will have
* at the end of the current grace period.
*/
-static __maybe_unused unsigned long rcu_exp_gp_seq_endval(struct rcu_state *rsp)
+static __maybe_unused unsigned long rcu_exp_gp_seq_endval(void)
{
- return rcu_seq_endval(&rsp->expedited_sequence);
+ return rcu_seq_endval(&rcu_state.expedited_sequence);
}
/*
* Record the end of an expedited grace period.
*/
-static void rcu_exp_gp_seq_end(struct rcu_state *rsp)
+static void rcu_exp_gp_seq_end(void)
{
- rcu_seq_end(&rsp->expedited_sequence);
+ rcu_seq_end(&rcu_state.expedited_sequence);
smp_mb(); /* Ensure that consecutive grace periods serialize. */
}
/*
- * Take a snapshot of the expedited-grace-period counter.
+ * Take a snapshot of the expedited-grace-period counter, which is the
+ * earliest value that will indicate that a full grace period has
+ * elapsed since the current time.
*/
-static unsigned long rcu_exp_gp_seq_snap(struct rcu_state *rsp)
+static unsigned long rcu_exp_gp_seq_snap(void)
{
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"));
+ s = rcu_seq_snap(&rcu_state.expedited_sequence);
+ trace_rcu_exp_grace_period(rcu_state.name, s, TPS("snap"));
return s;
}
@@ -66,9 +58,9 @@
* if a full expedited grace period has elapsed since that snapshot
* was taken.
*/
-static bool rcu_exp_gp_seq_done(struct rcu_state *rsp, unsigned long s)
+static bool rcu_exp_gp_seq_done(unsigned long s)
{
- return rcu_seq_done(&rsp->expedited_sequence, s);
+ return rcu_seq_done(&rcu_state.expedited_sequence, s);
}
/*
@@ -78,26 +70,26 @@
* 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)
+static void sync_exp_reset_tree_hotplug(void)
{
bool done;
unsigned long flags;
unsigned long mask;
unsigned long oldmask;
- int ncpus = smp_load_acquire(&rsp->ncpus); /* Order against locking. */
+ int ncpus = smp_load_acquire(&rcu_state.ncpus); /* Order vs. locking. */
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))
+ if (likely(ncpus == rcu_state.ncpus_snap))
return;
- rsp->ncpus_snap = ncpus;
+ rcu_state.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) {
+ rcu_for_each_leaf_node(rnp) {
raw_spin_lock_irqsave_rcu_node(rnp, flags);
if (rnp->expmaskinit == rnp->expmaskinitnext) {
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
@@ -135,16 +127,16 @@
* 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)
+static void __maybe_unused sync_exp_reset_tree(void)
{
unsigned long flags;
struct rcu_node *rnp;
- sync_exp_reset_tree_hotplug(rsp);
- rcu_for_each_node_breadth_first(rsp, rnp) {
+ sync_exp_reset_tree_hotplug();
+ rcu_for_each_node_breadth_first(rnp) {
raw_spin_lock_irqsave_rcu_node(rnp, flags);
WARN_ON_ONCE(rnp->expmask);
- rnp->expmask = rnp->expmaskinit;
+ WRITE_ONCE(rnp->expmask, rnp->expmaskinit);
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
}
}
@@ -153,31 +145,26 @@
* 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 specificed rcu_node structure's ->lock
+ * for the current expedited grace period.
*/
-static bool sync_rcu_preempt_exp_done(struct rcu_node *rnp)
+static bool sync_rcu_exp_done(struct rcu_node *rnp)
{
raw_lockdep_assert_held_rcu_node(rnp);
-
- return rnp->exp_tasks == NULL &&
+ return READ_ONCE(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
+ * Like sync_rcu_exp_done(), but where the caller does not hold the
+ * rcu_node's ->lock.
*/
-static bool sync_rcu_preempt_exp_done_unlocked(struct rcu_node *rnp)
+static bool sync_rcu_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);
+ ret = sync_rcu_exp_done(rnp);
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
return ret;
@@ -191,17 +178,16 @@
* 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 specified rcu_node structure's ->lock.
*/
-static void __rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
+static void __rcu_report_exp_rnp(struct rcu_node *rnp,
bool wake, unsigned long flags)
__releases(rnp->lock)
{
unsigned long mask;
+ raw_lockdep_assert_held_rcu_node(rnp);
for (;;) {
- if (!sync_rcu_preempt_exp_done(rnp)) {
+ if (!sync_rcu_exp_done(rnp)) {
if (!rnp->expmask)
rcu_initiate_boost(rnp, flags);
else
@@ -212,7 +198,7 @@
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
if (wake) {
smp_mb(); /* EGP done before wake_up(). */
- swake_up_one(&rsp->expedited_wq);
+ swake_up_one(&rcu_state.expedited_wq);
}
break;
}
@@ -221,7 +207,7 @@
rnp = rnp->parent;
raw_spin_lock_rcu_node(rnp); /* irqs already disabled */
WARN_ON_ONCE(!(rnp->expmask & mask));
- rnp->expmask &= ~mask;
+ WRITE_ONCE(rnp->expmask, rnp->expmask & ~mask);
}
}
@@ -229,49 +215,56 @@
* Report expedited quiescent state for specified node. This is a
* lock-acquisition wrapper function for __rcu_report_exp_rnp().
*/
-static void __maybe_unused rcu_report_exp_rnp(struct rcu_state *rsp,
- struct rcu_node *rnp, bool wake)
+static void __maybe_unused rcu_report_exp_rnp(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);
+ __rcu_report_exp_rnp(rnp, wake, flags);
}
/*
* Report expedited quiescent state for multiple CPUs, all covered by the
* specified leaf rcu_node structure.
*/
-static void rcu_report_exp_cpu_mult(struct rcu_state *rsp, struct rcu_node *rnp,
+static void rcu_report_exp_cpu_mult(struct rcu_node *rnp,
unsigned long mask, bool wake)
{
+ int cpu;
unsigned long flags;
+ struct rcu_data *rdp;
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. */
+ WRITE_ONCE(rnp->expmask, rnp->expmask & ~mask);
+ for_each_leaf_node_cpu_mask(rnp, cpu, mask) {
+ rdp = per_cpu_ptr(&rcu_data, cpu);
+ if (!IS_ENABLED(CONFIG_NO_HZ_FULL) || !rdp->rcu_forced_tick_exp)
+ continue;
+ rdp->rcu_forced_tick_exp = false;
+ tick_dep_clear_cpu(cpu, TICK_DEP_BIT_RCU_EXP);
+ }
+ __rcu_report_exp_rnp(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)
+static void rcu_report_exp_rdp(struct rcu_data *rdp)
{
- rcu_report_exp_cpu_mult(rsp, rdp->mynode, rdp->grpmask, wake);
+ WRITE_ONCE(rdp->exp_deferred_qs, false);
+ rcu_report_exp_cpu_mult(rdp->mynode, rdp->grpmask, true);
}
-/* Common code for synchronize_{rcu,sched}_expedited() work-done checking. */
-static bool sync_exp_work_done(struct rcu_state *rsp, unsigned long s)
+/* Common code for work-done checking. */
+static bool sync_exp_work_done(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(); /* ^^^ */
+ if (rcu_exp_gp_seq_done(s)) {
+ trace_rcu_exp_grace_period(rcu_state.name, s, TPS("done"));
+ smp_mb(); /* Ensure test happens before caller kfree(). */
return true;
}
return false;
@@ -284,28 +277,28 @@
* 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)
+static bool exp_funnel_lock(unsigned long s)
{
- struct rcu_data *rdp = per_cpu_ptr(rsp->rda, raw_smp_processor_id());
+ struct rcu_data *rdp = per_cpu_ptr(&rcu_data, raw_smp_processor_id());
struct rcu_node *rnp = rdp->mynode;
- struct rcu_node *rnp_root = rcu_get_root(rsp);
+ struct rcu_node *rnp_root = rcu_get_root();
/* 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_trylock(&rsp->exp_mutex))
+ mutex_trylock(&rcu_state.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
+ * otherwise falls through to acquire ->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, s))
+ if (sync_exp_work_done(s))
return true;
/* Work not done, either wait here or go up. */
@@ -314,66 +307,27 @@
/* Someone else doing GP, so wait for them. */
spin_unlock(&rnp->exp_lock);
- trace_rcu_exp_funnel_lock(rsp->name, rnp->level,
+ trace_rcu_exp_funnel_lock(rcu_state.name, rnp->level,
rnp->grplo, rnp->grphi,
TPS("wait"));
wait_event(rnp->exp_wq[rcu_seq_ctr(s) & 0x3],
- sync_exp_work_done(rsp, s));
+ sync_exp_work_done(s));
return true;
}
- rnp->exp_seq_rq = s; /* Followers can wait on us. */
+ WRITE_ONCE(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"));
+ trace_rcu_exp_funnel_lock(rcu_state.name, rnp->level,
+ rnp->grplo, rnp->grphi, TPS("nxtlvl"));
}
- mutex_lock(&rsp->exp_mutex);
+ mutex_lock(&rcu_state.exp_mutex);
fastpath:
- if (sync_exp_work_done(rsp, s)) {
- mutex_unlock(&rsp->exp_mutex);
+ if (sync_exp_work_done(s)) {
+ mutex_unlock(&rcu_state.exp_mutex);
return true;
}
- rcu_exp_gp_seq_start(rsp);
- trace_rcu_exp_grace_period(rsp->name, s, TPS("start"));
+ rcu_exp_gp_seq_start();
+ trace_rcu_exp_grace_period(rcu_state.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);
- /* Store .exp before .rcu_urgent_qs. */
- smp_store_release(this_cpu_ptr(&rcu_dynticks.rcu_urgent_qs), 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);
}
/*
@@ -384,31 +338,27 @@
{
int cpu;
unsigned long flags;
- smp_call_func_t func;
unsigned long mask_ofl_test;
unsigned long mask_ofl_ipi;
int ret;
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;
- func = rewp->rew_func;
raw_spin_lock_irqsave_rcu_node(rnp, flags);
/* 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);
+ struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
+ unsigned long mask = rdp->grpmask;
int snap;
if (raw_smp_processor_id() == cpu ||
!(rnp->qsmaskinitnext & mask)) {
mask_ofl_test |= mask;
} else {
- snap = rcu_dynticks_snap(rdtp);
+ snap = rcu_dynticks_snap(rdp);
if (rcu_dynticks_in_eqs(snap))
mask_ofl_test |= mask;
else
@@ -423,125 +373,172 @@
* until such time as the ->expmask bits are cleared.
*/
if (rcu_preempt_has_tasks(rnp))
- rnp->exp_tasks = rnp->blkd_tasks.next;
+ WRITE_ONCE(rnp->exp_tasks, rnp->blkd_tasks.next);
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
/* 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);
+ for_each_leaf_node_cpu_mask(rnp, cpu, mask_ofl_ipi) {
+ struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
+ unsigned long mask = rdp->grpmask;
- if (!(mask_ofl_ipi & mask))
- continue;
retry_ipi:
- if (rcu_dynticks_in_eqs_since(rdp->dynticks,
- rdp->exp_dynticks_snap)) {
+ if (rcu_dynticks_in_eqs_since(rdp, rdp->exp_dynticks_snap)) {
mask_ofl_test |= mask;
continue;
}
- ret = smp_call_function_single(cpu, func, rsp, 0);
- if (!ret) {
- mask_ofl_ipi &= ~mask;
+ if (get_cpu() == cpu) {
+ mask_ofl_test |= mask;
+ put_cpu();
continue;
}
+ ret = smp_call_function_single(cpu, rcu_exp_handler, NULL, 0);
+ put_cpu();
+ /* The CPU will report the QS in response to the IPI. */
+ if (!ret)
+ 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);
+ trace_rcu_exp_grace_period(rcu_state.name, rcu_exp_gp_seq_endval(), TPS("selectofl"));
+ schedule_timeout_idle(1);
goto retry_ipi;
}
- /* CPU really is offline, so we can ignore it. */
- if (!(rnp->expmask & mask))
- mask_ofl_ipi &= ~mask;
+ /* CPU really is offline, so we must report its QS. */
+ if (rnp->expmask & mask)
+ mask_ofl_test |= 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);
+ rcu_report_exp_cpu_mult(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)
+static void sync_rcu_exp_select_cpus(void)
{
+ int cpu;
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"));
+ trace_rcu_exp_grace_period(rcu_state.name, rcu_exp_gp_seq_endval(), TPS("reset"));
+ sync_exp_reset_tree();
+ trace_rcu_exp_grace_period(rcu_state.name, rcu_exp_gp_seq_endval(), TPS("select"));
/* Schedule work for each leaf rcu_node structure. */
- rcu_for_each_leaf_node(rsp, rnp) {
+ rcu_for_each_leaf_node(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 ||
- rcu_is_last_leaf_node(rsp, rnp)) {
+ rcu_is_last_leaf_node(rnp)) {
/* No workqueues yet or last leaf, do direct call. */
sync_rcu_exp_select_node_cpus(&rnp->rew.rew_work);
continue;
}
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);
+ cpu = find_next_bit(&rnp->ffmask, BITS_PER_LONG, -1);
+ /* If all offline, queue the work on an unbound CPU. */
+ if (unlikely(cpu > rnp->grphi - rnp->grplo))
+ cpu = WORK_CPU_UNBOUND;
+ else
+ cpu += rnp->grplo;
+ queue_work_on(cpu, 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)
+ rcu_for_each_leaf_node(rnp)
if (rnp->exp_need_flush)
flush_work(&rnp->rew.rew_work);
}
-static void synchronize_sched_expedited_wait(struct rcu_state *rsp)
+/*
+ * Wait for the expedited grace period to elapse, within time limit.
+ * If the time limit is exceeded without the grace period elapsing,
+ * return false, otherwise return true.
+ */
+static bool synchronize_rcu_expedited_wait_once(long tlimit)
+{
+ int t;
+ struct rcu_node *rnp_root = rcu_get_root();
+
+ t = swait_event_timeout_exclusive(rcu_state.expedited_wq,
+ sync_rcu_exp_done_unlocked(rnp_root),
+ tlimit);
+ // Workqueues should not be signaled.
+ if (t > 0 || sync_rcu_exp_done_unlocked(rnp_root))
+ return true;
+ WARN_ON(t < 0); /* workqueues should not be signaled. */
+ return false;
+}
+
+/*
+ * Wait for the expedited grace period to elapse, issuing any needed
+ * RCU CPU stall warnings along the way.
+ */
+static void synchronize_rcu_expedited_wait(void)
{
int cpu;
+ unsigned long j;
unsigned long jiffies_stall;
unsigned long jiffies_start;
unsigned long mask;
int ndetected;
+ struct rcu_data *rdp;
struct rcu_node *rnp;
- struct rcu_node *rnp_root = rcu_get_root(rsp);
- int ret;
+ struct rcu_node *rnp_root = rcu_get_root();
- trace_rcu_exp_grace_period(rsp->name, rcu_exp_gp_seq_endval(rsp), TPS("startwait"));
+ trace_rcu_exp_grace_period(rcu_state.name, rcu_exp_gp_seq_endval(), TPS("startwait"));
jiffies_stall = rcu_jiffies_till_stall_check();
jiffies_start = jiffies;
+ if (tick_nohz_full_enabled() && rcu_inkernel_boot_has_ended()) {
+ if (synchronize_rcu_expedited_wait_once(1))
+ return;
+ rcu_for_each_leaf_node(rnp) {
+ for_each_leaf_node_cpu_mask(rnp, cpu, rnp->expmask) {
+ rdp = per_cpu_ptr(&rcu_data, cpu);
+ if (rdp->rcu_forced_tick_exp)
+ continue;
+ rdp->rcu_forced_tick_exp = true;
+ preempt_disable();
+ if (cpu_online(cpu))
+ tick_dep_set_cpu(cpu, TICK_DEP_BIT_RCU_EXP);
+ preempt_enable();
+ }
+ }
+ j = READ_ONCE(jiffies_till_first_fqs);
+ if (synchronize_rcu_expedited_wait_once(j + HZ))
+ return;
+ WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_RT));
+ }
for (;;) {
- ret = swait_event_timeout_exclusive(
- rsp->expedited_wq,
- sync_rcu_preempt_exp_done_unlocked(rnp_root),
- jiffies_stall);
- if (ret > 0 || sync_rcu_preempt_exp_done_unlocked(rnp_root))
+ if (synchronize_rcu_expedited_wait_once(jiffies_stall))
return;
- WARN_ON(ret < 0); /* workqueues should not be signaled. */
- if (rcu_cpu_stall_suppress)
+ if (rcu_stall_is_suppressed())
continue;
panic_on_rcu_stall();
+ trace_rcu_stall_warning(rcu_state.name, TPS("ExpeditedStall"));
pr_err("INFO: %s detected expedited stalls on CPUs/tasks: {",
- rsp->name);
+ rcu_state.name);
ndetected = 0;
- rcu_for_each_leaf_node(rsp, rnp) {
+ rcu_for_each_leaf_node(rnp) {
ndetected += rcu_print_task_exp_stall(rnp);
for_each_leaf_node_possible_cpu(rnp, cpu) {
struct rcu_data *rdp;
mask = leaf_node_cpu_bit(rnp, cpu);
- if (!(rnp->expmask & mask))
+ if (!(READ_ONCE(rnp->expmask) & mask))
continue;
ndetected++;
- rdp = per_cpu_ptr(rsp->rda, cpu);
+ rdp = per_cpu_ptr(&rcu_data, cpu);
pr_cont(" %d-%c%c%c", cpu,
"O."[!!cpu_online(cpu)],
"o."[!!(rdp->grpmask & rnp->expmaskinit)],
@@ -549,28 +546,31 @@
}
}
pr_cont(" } %lu jiffies s: %lu root: %#lx/%c\n",
- jiffies - jiffies_start, rsp->expedited_sequence,
- rnp_root->expmask, ".T"[!!rnp_root->exp_tasks]);
+ jiffies - jiffies_start, rcu_state.expedited_sequence,
+ data_race(rnp_root->expmask),
+ ".T"[!!data_race(rnp_root->exp_tasks)]);
if (ndetected) {
pr_err("blocking rcu_node structures:");
- rcu_for_each_node_breadth_first(rsp, rnp) {
+ rcu_for_each_node_breadth_first(rnp) {
if (rnp == rnp_root)
continue; /* printed unconditionally */
- if (sync_rcu_preempt_exp_done_unlocked(rnp))
+ if (sync_rcu_exp_done_unlocked(rnp))
continue;
pr_cont(" l=%u:%d-%d:%#lx/%c",
rnp->level, rnp->grplo, rnp->grphi,
- rnp->expmask,
- ".T"[!!rnp->exp_tasks]);
+ data_race(rnp->expmask),
+ ".T"[!!data_race(rnp->exp_tasks)]);
}
pr_cont("\n");
}
- rcu_for_each_leaf_node(rsp, rnp) {
+ rcu_for_each_leaf_node(rnp) {
for_each_leaf_node_possible_cpu(rnp, cpu) {
mask = leaf_node_cpu_bit(rnp, cpu);
- if (!(rnp->expmask & mask))
+ if (!(READ_ONCE(rnp->expmask) & mask))
continue;
+ preempt_disable(); // For smp_processor_id() in dump_cpu_task().
dump_cpu_task(cpu);
+ preempt_enable();
}
}
jiffies_stall = 3 * rcu_jiffies_till_stall_check() + 3;
@@ -583,47 +583,45 @@
* 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)
+static void rcu_exp_wait_wake(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"));
+ synchronize_rcu_expedited_wait();
- /*
- * Switch over to wakeup mode, allowing the next GP, but -only- the
- * next GP, to proceed.
- */
- mutex_lock(&rsp->exp_wake_mutex);
+ // Switch over to wakeup mode, allowing the next GP to proceed.
+ // End the previous grace period only after acquiring the mutex
+ // to ensure that only one GP runs concurrently with wakeups.
+ mutex_lock(&rcu_state.exp_wake_mutex);
+ rcu_exp_gp_seq_end();
+ trace_rcu_exp_grace_period(rcu_state.name, s, TPS("end"));
- rcu_for_each_node_breadth_first(rsp, rnp) {
+ rcu_for_each_node_breadth_first(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;
+ WRITE_ONCE(rnp->exp_seq_rq, s);
spin_unlock(&rnp->exp_lock);
}
smp_mb(); /* All above changes before wakeup. */
wake_up_all(&rnp->exp_wq[rcu_seq_ctr(s) & 0x3]);
}
- trace_rcu_exp_grace_period(rsp->name, s, TPS("endwake"));
- mutex_unlock(&rsp->exp_wake_mutex);
+ trace_rcu_exp_grace_period(rcu_state.name, s, TPS("endwake"));
+ mutex_unlock(&rcu_state.exp_wake_mutex);
}
/*
* Common code to drive an expedited grace period forward, used by
* workqueues and mid-boot-time tasks.
*/
-static void rcu_exp_sel_wait_wake(struct rcu_state *rsp,
- smp_call_func_t func, unsigned long s)
+static void rcu_exp_sel_wait_wake(unsigned long s)
{
/* Initialize the rcu_node tree in preparation for the wait. */
- sync_rcu_exp_select_cpus(rsp, func);
+ sync_rcu_exp_select_cpus();
/* Wait and clean up, including waking everyone. */
- rcu_exp_wait_wake(rsp, s);
+ rcu_exp_wait_wake(s);
}
/*
@@ -634,88 +632,8 @@
struct rcu_exp_work *rewp;
rewp = container_of(wp, struct rcu_exp_work, rew_work);
- rcu_exp_sel_wait_wake(rewp->rew_rsp, rewp->rew_func, rewp->rew_s);
+ rcu_exp_sel_wait_wake(rewp->rew_s);
}
-
-/*
- * Given an rcu_state pointer and a smp_call_function() handler, kick
- * off the specified flavor of expedited grace period.
- */
-static void _synchronize_rcu_expedited(struct rcu_state *rsp,
- smp_call_func_t func)
-{
- struct rcu_data *rdp;
- struct rcu_exp_work rew;
- struct rcu_node *rnp;
- unsigned long s;
-
- /* If expedited grace periods are prohibited, fall back to normal. */
- if (rcu_gp_is_normal()) {
- wait_rcu_gp(rsp->call);
- 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. */
-
- /* Ensure that load happens before action based on it. */
- if (unlikely(rcu_scheduler_active == RCU_SCHEDULER_INIT)) {
- /* Direct call during scheduler init and early_initcalls(). */
- rcu_exp_sel_wait_wake(rsp, func, s);
- } else {
- /* Marshall arguments & schedule the expedited grace period. */
- rew.rew_func = func;
- rew.rew_rsp = rsp;
- rew.rew_s = s;
- INIT_WORK_ONSTACK(&rew.rew_work, wait_rcu_exp_gp);
- queue_work(rcu_gp_wq, &rew.rew_work);
- }
-
- /* Wait for expedited grace period to complete. */
- 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, s));
- smp_mb(); /* Workqueue actions happen before return. */
-
- /* Let the next expedited grace period start. */
- mutex_unlock(&rsp->exp_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)
-{
- struct rcu_state *rsp = &rcu_sched_state;
-
- RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) ||
- lock_is_held(&rcu_lock_map) ||
- lock_is_held(&rcu_sched_lock_map),
- "Illegal synchronize_sched_expedited() in RCU read-side critical section");
-
- /* If only one CPU, this is automatically a grace period. */
- if (rcu_blocking_is_gp())
- return;
-
- _synchronize_rcu_expedited(rsp, sync_sched_exp_handler);
-}
-EXPORT_SYMBOL_GPL(synchronize_sched_expedited);
#ifdef CONFIG_PREEMPT_RCU
@@ -726,79 +644,234 @@
* ->expmask fields in the rcu_node tree. Otherwise, immediately
* report the quiescent state.
*/
-static void sync_rcu_exp_handler(void *info)
+static void rcu_exp_handler(void *unused)
{
- struct rcu_data *rdp;
- struct rcu_state *rsp = info;
+ int depth = rcu_preempt_depth();
+ unsigned long flags;
+ struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
+ struct rcu_node *rnp = rdp->mynode;
struct task_struct *t = current;
/*
- * Within an RCU read-side critical section, request that the next
- * rcu_read_unlock() report. Unless this RCU read-side critical
- * section has already blocked, in which case it is already set
- * up for the expedited grace period to wait on it.
+ * First, the common case of not being in an RCU read-side
+ * critical section. If also enabled or idle, immediately
+ * report the quiescent state, otherwise defer.
*/
- if (t->rcu_read_lock_nesting > 0 &&
- !t->rcu_read_unlock_special.b.blocked) {
- t->rcu_read_unlock_special.b.exp_need_qs = true;
+ if (!depth) {
+ if (!(preempt_count() & (PREEMPT_MASK | SOFTIRQ_MASK)) ||
+ rcu_dynticks_curr_cpu_in_eqs()) {
+ rcu_report_exp_rdp(rdp);
+ } else {
+ rdp->exp_deferred_qs = true;
+ set_tsk_need_resched(t);
+ set_preempt_need_resched();
+ }
return;
}
/*
- * We are either exiting an RCU read-side critical section (negative
- * values of t->rcu_read_lock_nesting) or are not in one at all
- * (zero value of t->rcu_read_lock_nesting). Or we are in an RCU
- * read-side critical section that blocked before this expedited
- * grace period started. Either way, we can immediately report
- * the quiescent state.
+ * Second, the less-common case of being in an RCU read-side
+ * critical section. In this case we can count on a future
+ * rcu_read_unlock(). However, this rcu_read_unlock() might
+ * execute on some other CPU, but in that case there will be
+ * a future context switch. Either way, if the expedited
+ * grace period is still waiting on this CPU, set ->deferred_qs
+ * so that the eventual quiescent state will be reported.
+ * Note that there is a large group of race conditions that
+ * can have caused this quiescent state to already have been
+ * reported, so we really do need to check ->expmask.
*/
- rdp = this_cpu_ptr(rsp->rda);
- rcu_report_exp_rdp(rsp, rdp, true);
+ if (depth > 0) {
+ raw_spin_lock_irqsave_rcu_node(rnp, flags);
+ if (rnp->expmask & rdp->grpmask) {
+ rdp->exp_deferred_qs = true;
+ t->rcu_read_unlock_special.b.exp_hint = true;
+ }
+ raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
+ return;
+ }
+
+ // Finally, negative nesting depth should not happen.
+ WARN_ON_ONCE(1);
}
+
+/* PREEMPTION=y, so no PREEMPTION=n expedited grace period to clean up after. */
+static void sync_sched_exp_online_cleanup(int cpu)
+{
+}
+
+/*
+ * Scan the current list of tasks blocked within RCU read-side critical
+ * sections, printing out the tid of each that is blocking the current
+ * expedited grace period.
+ */
+static int rcu_print_task_exp_stall(struct rcu_node *rnp)
+{
+ unsigned long flags;
+ int ndetected = 0;
+ struct task_struct *t;
+
+ raw_spin_lock_irqsave_rcu_node(rnp, flags);
+ if (!rnp->exp_tasks) {
+ raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
+ return 0;
+ }
+ t = list_entry(rnp->exp_tasks->prev,
+ struct task_struct, rcu_node_entry);
+ list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) {
+ pr_cont(" P%d", t->pid);
+ ndetected++;
+ }
+ raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
+ return ndetected;
+}
+
+#else /* #ifdef CONFIG_PREEMPT_RCU */
+
+/* Request an expedited quiescent state. */
+static void rcu_exp_need_qs(void)
+{
+ __this_cpu_write(rcu_data.cpu_no_qs.b.exp, true);
+ /* Store .exp before .rcu_urgent_qs. */
+ smp_store_release(this_cpu_ptr(&rcu_data.rcu_urgent_qs), true);
+ set_tsk_need_resched(current);
+ set_preempt_need_resched();
+}
+
+/* Invoked on each online non-idle CPU for expedited quiescent state. */
+static void rcu_exp_handler(void *unused)
+{
+ struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
+ struct rcu_node *rnp = rdp->mynode;
+
+ if (!(READ_ONCE(rnp->expmask) & rdp->grpmask) ||
+ __this_cpu_read(rcu_data.cpu_no_qs.b.exp))
+ return;
+ if (rcu_is_cpu_rrupt_from_idle()) {
+ rcu_report_exp_rdp(this_cpu_ptr(&rcu_data));
+ return;
+ }
+ rcu_exp_need_qs();
+}
+
+/* Send IPI for expedited cleanup if needed at end of CPU-hotplug operation. */
+static void sync_sched_exp_online_cleanup(int cpu)
+{
+ unsigned long flags;
+ int my_cpu;
+ struct rcu_data *rdp;
+ int ret;
+ struct rcu_node *rnp;
+
+ rdp = per_cpu_ptr(&rcu_data, cpu);
+ rnp = rdp->mynode;
+ my_cpu = get_cpu();
+ /* Quiescent state either not needed or already requested, leave. */
+ if (!(READ_ONCE(rnp->expmask) & rdp->grpmask) ||
+ rdp->cpu_no_qs.b.exp) {
+ put_cpu();
+ return;
+ }
+ /* Quiescent state needed on current CPU, so set it up locally. */
+ if (my_cpu == cpu) {
+ local_irq_save(flags);
+ rcu_exp_need_qs();
+ local_irq_restore(flags);
+ put_cpu();
+ return;
+ }
+ /* Quiescent state needed on some other CPU, send IPI. */
+ ret = smp_call_function_single(cpu, rcu_exp_handler, NULL, 0);
+ put_cpu();
+ WARN_ON_ONCE(ret);
+}
+
+/*
+ * Because preemptible RCU does not exist, we never have to check for
+ * tasks blocked within RCU read-side critical sections that are
+ * blocking the current expedited grace period.
+ */
+static int rcu_print_task_exp_stall(struct rcu_node *rnp)
+{
+ return 0;
+}
+
+#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
/**
* synchronize_rcu_expedited - Brute-force RCU grace period
*
- * Wait for an RCU-preempt grace period, but expedite it. The basic
- * idea is to IPI all non-idle non-nohz online CPUs. The IPI handler
- * checks whether the CPU is in an RCU-preempt critical section, and
- * if so, it sets a flag that causes the outermost rcu_read_unlock()
- * to report the quiescent state. On the other hand, if the CPU is
- * not in an RCU read-side critical section, the IPI handler reports
- * the quiescent state immediately.
+ * Wait for an RCU grace period, but expedite it. The basic idea is to
+ * IPI all non-idle non-nohz online CPUs. The IPI handler checks whether
+ * the CPU is in an RCU critical section, and if so, it sets a flag that
+ * causes the outermost rcu_read_unlock() to report the quiescent state
+ * for RCU-preempt or asks the scheduler for help for RCU-sched. On the
+ * other hand, if the CPU is not in an RCU read-side critical section,
+ * the IPI handler reports the quiescent state immediately.
*
- * Although this is a greate improvement over previous expedited
+ * Although this is a great improvement over previous expedited
* implementations, it is still unfriendly to real-time workloads, so is
* thus not recommended for any sort of common-case code. In fact, if
* you are using synchronize_rcu_expedited() in a loop, please restructure
- * your code to batch your updates, and then Use a single synchronize_rcu()
+ * your code to batch your updates, and then use a single synchronize_rcu()
* instead.
+ *
+ * This has the same semantics as (but is more brutal than) synchronize_rcu().
*/
void synchronize_rcu_expedited(void)
{
- struct rcu_state *rsp = rcu_state_p;
+ bool no_wq;
+ struct rcu_exp_work rew;
+ struct rcu_node *rnp;
+ unsigned long s;
RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) ||
lock_is_held(&rcu_lock_map) ||
lock_is_held(&rcu_sched_lock_map),
"Illegal synchronize_rcu_expedited() in RCU read-side critical section");
- if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE)
+ /* Is the state is such that the call is a grace period? */
+ if (rcu_blocking_is_gp())
return;
- _synchronize_rcu_expedited(rsp, sync_rcu_exp_handler);
+
+ /* If expedited grace periods are prohibited, fall back to normal. */
+ if (rcu_gp_is_normal()) {
+ wait_rcu_gp(call_rcu);
+ return;
+ }
+
+ /* Take a snapshot of the sequence number. */
+ s = rcu_exp_gp_seq_snap();
+ if (exp_funnel_lock(s))
+ return; /* Someone else did our work for us. */
+
+ /* Don't use workqueue during boot or from an incoming CPU. */
+ preempt_disable();
+ no_wq = rcu_scheduler_active == RCU_SCHEDULER_INIT ||
+ !cpumask_test_cpu(smp_processor_id(), cpu_active_mask);
+ preempt_enable();
+
+ /* Ensure that load happens before action based on it. */
+ if (unlikely(no_wq)) {
+ /* Direct call for scheduler init, early_initcall()s, and incoming CPUs. */
+ rcu_exp_sel_wait_wake(s);
+ } else {
+ /* Marshall arguments & schedule the expedited grace period. */
+ rew.rew_s = s;
+ INIT_WORK_ONSTACK(&rew.rew_work, wait_rcu_exp_gp);
+ queue_work(rcu_gp_wq, &rew.rew_work);
+ }
+
+ /* Wait for expedited grace period to complete. */
+ rnp = rcu_get_root();
+ wait_event(rnp->exp_wq[rcu_seq_ctr(s) & 0x3],
+ sync_exp_work_done(s));
+ smp_mb(); /* Workqueue actions happen before return. */
+
+ /* Let the next expedited grace period start. */
+ mutex_unlock(&rcu_state.exp_mutex);
+
+ if (likely(!no_wq))
+ destroy_work_on_stack(&rew.rew_work);
}
EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
-
-#else /* #ifdef CONFIG_PREEMPT_RCU */
-
-/*
- * Wait for an rcu-preempt grace period, but make it happen quickly.
- * But because preemptible RCU does not exist, map to rcu-sched.
- */
-void synchronize_rcu_expedited(void)
-{
- synchronize_sched_expedited();
-}
-EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
-
-#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
--
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