forked from luck/tmp_suning_uos_patched
31945aa9f1
doc.2017.01.15b: Documentation updates dyntick.2017.01.23a: Dyntick tracking consolidation fixes.2017.01.23a: Miscellaneous fixes srcu.2017.01.25a: SRCU rewrite, fixes, and verification torture.2017.01.15b: Torture-test updates
750 lines
22 KiB
C
750 lines
22 KiB
C
/*
|
|
* 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>
|
|
*/
|
|
|
|
/*
|
|
* Record the start of an expedited grace period.
|
|
*/
|
|
static void rcu_exp_gp_seq_start(struct rcu_state *rsp)
|
|
{
|
|
rcu_seq_start(&rsp->expedited_sequence);
|
|
}
|
|
|
|
/*
|
|
* Record the end of an expedited grace period.
|
|
*/
|
|
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. */
|
|
}
|
|
|
|
/*
|
|
* Take a snapshot of the expedited-grace-period counter.
|
|
*/
|
|
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;
|
|
}
|
|
|
|
/*
|
|
* Given a counter snapshot from rcu_exp_gp_seq_snap(), return true
|
|
* 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)
|
|
{
|
|
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_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_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_each_leaf_node_possible_cpu(rnp, cpu) {
|
|
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
|
|
|
|
rdp->exp_dynticks_snap =
|
|
rcu_dynticks_snap(rdp->dynticks);
|
|
if (raw_smp_processor_id() == cpu ||
|
|
rcu_dynticks_in_eqs(rdp->exp_dynticks_snap) ||
|
|
!(rnp->qsmaskinitnext & rdp->grpmask))
|
|
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. */
|
|
for_each_leaf_node_possible_cpu(rnp, cpu) {
|
|
unsigned long mask = leaf_node_cpu_bit(rnp, cpu);
|
|
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
|
|
|
|
if (!(mask_ofl_ipi & mask))
|
|
continue;
|
|
retry_ipi:
|
|
if (rcu_dynticks_in_eqs_since(rdp->dynticks,
|
|
rdp->exp_dynticks_snap)) {
|
|
mask_ofl_test |= mask;
|
|
continue;
|
|
}
|
|
ret = smp_call_function_single(cpu, func, rsp, 0);
|
|
if (!ret) {
|
|
mask_ofl_ipi &= ~mask;
|
|
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);
|
|
schedule_timeout_uninterruptible(1);
|
|
goto retry_ipi;
|
|
}
|
|
/* CPU really is offline, so we can ignore it. */
|
|
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;
|
|
WARN_ON(ret < 0); /* workqueues should not be signaled. */
|
|
if (rcu_cpu_stall_suppress)
|
|
continue;
|
|
panic_on_rcu_stall();
|
|
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);
|
|
for_each_leaf_node_possible_cpu(rnp, cpu) {
|
|
struct rcu_data *rdp;
|
|
|
|
mask = leaf_node_cpu_bit(rnp, cpu);
|
|
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)]);
|
|
}
|
|
}
|
|
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) {
|
|
for_each_leaf_node_possible_cpu(rnp, cpu) {
|
|
mask = leaf_node_cpu_bit(rnp, cpu);
|
|
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);
|
|
|
|
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);
|
|
}
|
|
|
|
/* Let the workqueue handler know what it is supposed to do. */
|
|
struct rcu_exp_work {
|
|
smp_call_func_t rew_func;
|
|
struct rcu_state *rew_rsp;
|
|
unsigned long rew_s;
|
|
struct work_struct rew_work;
|
|
};
|
|
|
|
/*
|
|
* 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)
|
|
{
|
|
/* Initialize the rcu_node tree in preparation for the wait. */
|
|
sync_rcu_exp_select_cpus(rsp, func);
|
|
|
|
/* Wait and clean up, including waking everyone. */
|
|
rcu_exp_wait_wake(rsp, s);
|
|
}
|
|
|
|
/*
|
|
* Work-queue handler to drive an expedited grace period forward.
|
|
*/
|
|
static void wait_rcu_exp_gp(struct work_struct *wp)
|
|
{
|
|
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);
|
|
}
|
|
|
|
/*
|
|
* 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);
|
|
schedule_work(&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[(s >> 1) & 0x3],
|
|
sync_exp_work_done(rsp,
|
|
&rdp->exp_workdone0, s));
|
|
|
|
/* 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
|
|
|
|
/*
|
|
* Remote handler for smp_call_function_single(). If there is an
|
|
* RCU read-side critical section in effect, request that the
|
|
* next rcu_read_unlock() record the quiescent state up the
|
|
* ->expmask fields in the rcu_node tree. Otherwise, immediately
|
|
* report the quiescent state.
|
|
*/
|
|
static void sync_rcu_exp_handler(void *info)
|
|
{
|
|
struct rcu_data *rdp;
|
|
struct rcu_state *rsp = info;
|
|
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.
|
|
*/
|
|
if (t->rcu_read_lock_nesting > 0 &&
|
|
!t->rcu_read_unlock_special.b.blocked) {
|
|
t->rcu_read_unlock_special.b.exp_need_qs = true;
|
|
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.
|
|
*/
|
|
rdp = this_cpu_ptr(rsp->rda);
|
|
rcu_report_exp_rdp(rsp, rdp, true);
|
|
}
|
|
|
|
/**
|
|
* 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.
|
|
*
|
|
* Although this is a greate 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()
|
|
* instead.
|
|
*/
|
|
void synchronize_rcu_expedited(void)
|
|
{
|
|
struct rcu_state *rsp = rcu_state_p;
|
|
|
|
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)
|
|
return;
|
|
_synchronize_rcu_expedited(rsp, sync_rcu_exp_handler);
|
|
}
|
|
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 */
|
|
|
|
/*
|
|
* Switch to run-time mode once Tree RCU has fully initialized.
|
|
*/
|
|
static int __init rcu_exp_runtime_mode(void)
|
|
{
|
|
rcu_test_sync_prims();
|
|
rcu_scheduler_active = RCU_SCHEDULER_RUNNING;
|
|
rcu_test_sync_prims();
|
|
return 0;
|
|
}
|
|
core_initcall(rcu_exp_runtime_mode);
|