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rcu: Eliminate grace-period management code use of rsp

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Now that there is only one rcu_state structure, there is less point
in maintaining a pointer to it.  This commit therefore replaces
rsp with &rcu_state in rcu_start_this_gp(), rcu_accelerate_cbs(),
__note_gp_changes(), rcu_gp_init(), rcu_gp_fqs(), rcu_gp_cleanup(),
rcu_gp_kthread(), and rcu_report_qs_rsp().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2018-07-05 15:47:01 -07:00
parent 4c6ed43708
commit 9cbc5b9702
1 changed files with 82 additions and 86 deletions
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166
kernel/rcu/tree.c
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@ -1525,7 +1525,6 @@ static bool rcu_start_this_gp(struct rcu_node *rnp_start, struct rcu_data *rdp,
unsigned long gp_seq_req)
{
bool ret = false;
struct rcu_state *rsp = &rcu_state;
struct rcu_node *rnp;
/*
@ -1574,13 +1573,13 @@ static bool rcu_start_this_gp(struct rcu_node *rnp_start, struct rcu_data *rdp,
goto unlock_out;
}
trace_rcu_this_gp(rnp, rdp, gp_seq_req, TPS("Startedroot"));
WRITE_ONCE(rsp->gp_flags, rsp->gp_flags | RCU_GP_FLAG_INIT);
rsp->gp_req_activity = jiffies;
if (!rsp->gp_kthread) {
WRITE_ONCE(rcu_state.gp_flags, rcu_state.gp_flags | RCU_GP_FLAG_INIT);
rcu_state.gp_req_activity = jiffies;
if (!rcu_state.gp_kthread) {
trace_rcu_this_gp(rnp, rdp, gp_seq_req, TPS("NoGPkthread"));
goto unlock_out;
}
trace_rcu_grace_period(rsp->name, READ_ONCE(rsp->gp_seq), TPS("newreq"));
trace_rcu_grace_period(rcu_state.name, READ_ONCE(rcu_state.gp_seq), TPS("newreq"));
ret = true; /* Caller must wake GP kthread. */
unlock_out:
/* Push furthest requested GP to leaf node and rcu_data structure. */
@ -1642,7 +1641,6 @@ static bool rcu_accelerate_cbs(struct rcu_node *rnp, struct rcu_data *rdp)
{
unsigned long gp_seq_req;
bool ret = false;
struct rcu_state *rsp = &rcu_state;
raw_lockdep_assert_held_rcu_node(rnp);
@ -1660,15 +1658,15 @@ static bool rcu_accelerate_cbs(struct rcu_node *rnp, struct rcu_data *rdp)
* accelerating callback invocation to an earlier grace-period
* number.
*/
gp_seq_req = rcu_seq_snap(&rsp->gp_seq);
gp_seq_req = rcu_seq_snap(&rcu_state.gp_seq);
if (rcu_segcblist_accelerate(&rdp->cblist, gp_seq_req))
ret = rcu_start_this_gp(rnp, rdp, gp_seq_req);
/* Trace depending on how much we were able to accelerate. */
if (rcu_segcblist_restempty(&rdp->cblist, RCU_WAIT_TAIL))
trace_rcu_grace_period(rsp->name, rdp->gp_seq, TPS("AccWaitCB"));
trace_rcu_grace_period(rcu_state.name, rdp->gp_seq, TPS("AccWaitCB"));
else
trace_rcu_grace_period(rsp->name, rdp->gp_seq, TPS("AccReadyCB"));
trace_rcu_grace_period(rcu_state.name, rdp->gp_seq, TPS("AccReadyCB"));
return ret;
}
@ -1737,7 +1735,6 @@ static bool __note_gp_changes(struct rcu_node *rnp, struct rcu_data *rdp)
{
bool ret;
bool need_gp;
struct rcu_state __maybe_unused *rsp = &rcu_state;
raw_lockdep_assert_held_rcu_node(rnp);
@ -1748,7 +1745,7 @@ static bool __note_gp_changes(struct rcu_node *rnp, struct rcu_data *rdp)
if (rcu_seq_completed_gp(rdp->gp_seq, rnp->gp_seq) ||
unlikely(READ_ONCE(rdp->gpwrap))) {
ret = rcu_advance_cbs(rnp, rdp); /* Advance callbacks. */
trace_rcu_grace_period(rsp->name, rdp->gp_seq, TPS("cpuend"));
trace_rcu_grace_period(rcu_state.name, rdp->gp_seq, TPS("cpuend"));
} else {
ret = rcu_accelerate_cbs(rnp, rdp); /* Recent callbacks. */
}
@ -1761,7 +1758,7 @@ static bool __note_gp_changes(struct rcu_node *rnp, struct rcu_data *rdp)
* set up to detect a quiescent state, otherwise don't
* go looking for one.
*/
trace_rcu_grace_period(rsp->name, rnp->gp_seq, TPS("cpustart"));
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->rcu_qs_ctr_snap = __this_cpu_read(rcu_dynticks.rcu_qs_ctr);
@ -1814,16 +1811,15 @@ static bool rcu_gp_init(void)
unsigned long mask;
struct rcu_data *rdp;
struct rcu_node *rnp = rcu_get_root();
struct rcu_state *rsp = &rcu_state;
WRITE_ONCE(rsp->gp_activity, jiffies);
WRITE_ONCE(rcu_state.gp_activity, jiffies);
raw_spin_lock_irq_rcu_node(rnp);
if (!READ_ONCE(rsp->gp_flags)) {
if (!READ_ONCE(rcu_state.gp_flags)) {
/* Spurious wakeup, tell caller to go back to sleep. */
raw_spin_unlock_irq_rcu_node(rnp);
return false;
}
WRITE_ONCE(rsp->gp_flags, 0); /* Clear all flags: New grace period. */
WRITE_ONCE(rcu_state.gp_flags, 0); /* Clear all flags: New GP. */
if (WARN_ON_ONCE(rcu_gp_in_progress())) {
/*
@ -1837,8 +1833,8 @@ static bool rcu_gp_init(void)
/* Advance to a new grace period and initialize state. */
record_gp_stall_check_time();
/* Record GP times before starting GP, hence rcu_seq_start(). */
rcu_seq_start(&rsp->gp_seq);
trace_rcu_grace_period(rsp->name, rsp->gp_seq, TPS("start"));
rcu_seq_start(&rcu_state.gp_seq);
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, TPS("start"));
raw_spin_unlock_irq_rcu_node(rnp);
/*
@ -1847,15 +1843,15 @@ static bool rcu_gp_init(void)
* for subsequent online CPUs, and that quiescent-state forcing
* will handle subsequent offline CPUs.
*/
rsp->gp_state = RCU_GP_ONOFF;
rcu_state.gp_state = RCU_GP_ONOFF;
rcu_for_each_leaf_node(rnp) {
spin_lock(&rsp->ofl_lock);
spin_lock(&rcu_state.ofl_lock);
raw_spin_lock_irq_rcu_node(rnp);
if (rnp->qsmaskinit == rnp->qsmaskinitnext &&
!rnp->wait_blkd_tasks) {
/* Nothing to do on this leaf rcu_node structure. */
raw_spin_unlock_irq_rcu_node(rnp);
spin_unlock(&rsp->ofl_lock);
spin_unlock(&rcu_state.ofl_lock);
continue;
}
@ -1891,34 +1887,34 @@ static bool rcu_gp_init(void)
}
raw_spin_unlock_irq_rcu_node(rnp);
spin_unlock(&rsp->ofl_lock);
spin_unlock(&rcu_state.ofl_lock);
}
rcu_gp_slow(gp_preinit_delay); /* Races with CPU hotplug. */
/*
* Set the quiescent-state-needed bits in all the rcu_node
* structures for all currently online CPUs in breadth-first order,
* starting from the root rcu_node structure, relying on the layout
* 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.
* structures for all currently online CPUs in breadth-first
* order, starting from the root rcu_node structure, relying on the
* layout of the tree within the rcu_state.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.
*
* The grace period cannot complete until the initialization
* process finishes, because this kthread handles both.
*/
rsp->gp_state = RCU_GP_INIT;
rcu_state.gp_state = RCU_GP_INIT;
rcu_for_each_node_breadth_first(rnp) {
rcu_gp_slow(gp_init_delay);
raw_spin_lock_irqsave_rcu_node(rnp, flags);
rdp = this_cpu_ptr(&rcu_data);
rcu_preempt_check_blocked_tasks(rnp);
rnp->qsmask = rnp->qsmaskinit;
WRITE_ONCE(rnp->gp_seq, rsp->gp_seq);
WRITE_ONCE(rnp->gp_seq, rcu_state.gp_seq);
if (rnp == rdp->mynode)
(void)__note_gp_changes(rnp, rdp);
rcu_preempt_boost_start_gp(rnp);
trace_rcu_grace_period_init(rsp->name, rnp->gp_seq,
trace_rcu_grace_period_init(rcu_state.name, rnp->gp_seq,
rnp->level, rnp->grplo,
rnp->grphi, rnp->qsmask);
/* Quiescent states for tasks on any now-offline CPUs. */
@ -1929,7 +1925,7 @@ static bool rcu_gp_init(void)
else
raw_spin_unlock_irq_rcu_node(rnp);
cond_resched_tasks_rcu_qs();
WRITE_ONCE(rsp->gp_activity, jiffies);
WRITE_ONCE(rcu_state.gp_activity, jiffies);
}
return true;
@ -1961,10 +1957,9 @@ static bool rcu_gp_fqs_check_wake(int *gfp)
static void rcu_gp_fqs(bool first_time)
{
struct rcu_node *rnp = rcu_get_root();
struct rcu_state *rsp = &rcu_state;
WRITE_ONCE(rsp->gp_activity, jiffies);
rsp->n_force_qs++;
WRITE_ONCE(rcu_state.gp_activity, jiffies);
rcu_state.n_force_qs++;
if (first_time) {
/* Collect dyntick-idle snapshots. */
force_qs_rnp(dyntick_save_progress_counter);
@ -1973,10 +1968,10 @@ static void rcu_gp_fqs(bool first_time)
force_qs_rnp(rcu_implicit_dynticks_qs);
}
/* Clear flag to prevent immediate re-entry. */
if (READ_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) {
if (READ_ONCE(rcu_state.gp_flags) & RCU_GP_FLAG_FQS) {
raw_spin_lock_irq_rcu_node(rnp);
WRITE_ONCE(rsp->gp_flags,
READ_ONCE(rsp->gp_flags) & ~RCU_GP_FLAG_FQS);
WRITE_ONCE(rcu_state.gp_flags,
READ_ONCE(rcu_state.gp_flags) & ~RCU_GP_FLAG_FQS);
raw_spin_unlock_irq_rcu_node(rnp);
}
}
@ -1991,14 +1986,13 @@ static void rcu_gp_cleanup(void)
unsigned long new_gp_seq;
struct rcu_data *rdp;
struct rcu_node *rnp = rcu_get_root();
struct rcu_state *rsp = &rcu_state;
struct swait_queue_head *sq;
WRITE_ONCE(rsp->gp_activity, jiffies);
WRITE_ONCE(rcu_state.gp_activity, jiffies);
raw_spin_lock_irq_rcu_node(rnp);
gp_duration = jiffies - rsp->gp_start;
if (gp_duration > rsp->gp_max)
rsp->gp_max = gp_duration;
gp_duration = jiffies - rcu_state.gp_start;
if (gp_duration > rcu_state.gp_max)
rcu_state.gp_max = gp_duration;
/*
* We know the grace period is complete, but to everyone else
@ -2019,7 +2013,7 @@ static void rcu_gp_cleanup(void)
* the rcu_node structures before the beginning of the next grace
* period is recorded in any of the rcu_node structures.
*/
new_gp_seq = rsp->gp_seq;
new_gp_seq = rcu_state.gp_seq;
rcu_seq_end(&new_gp_seq);
rcu_for_each_node_breadth_first(rnp) {
raw_spin_lock_irq_rcu_node(rnp);
@ -2036,16 +2030,16 @@ static void rcu_gp_cleanup(void)
raw_spin_unlock_irq_rcu_node(rnp);
rcu_nocb_gp_cleanup(sq);
cond_resched_tasks_rcu_qs();
WRITE_ONCE(rsp->gp_activity, jiffies);
WRITE_ONCE(rcu_state.gp_activity, jiffies);
rcu_gp_slow(gp_cleanup_delay);
}
rnp = rcu_get_root();
raw_spin_lock_irq_rcu_node(rnp); /* GP before rsp->gp_seq update. */
raw_spin_lock_irq_rcu_node(rnp); /* GP before ->gp_seq update. */
/* Declare grace period done. */
rcu_seq_end(&rsp->gp_seq);
trace_rcu_grace_period(rsp->name, rsp->gp_seq, TPS("end"));
rsp->gp_state = RCU_GP_IDLE;
rcu_seq_end(&rcu_state.gp_seq);
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, TPS("end"));
rcu_state.gp_state = RCU_GP_IDLE;
/* Check for GP requests since above loop. */
rdp = this_cpu_ptr(&rcu_data);
if (!needgp && ULONG_CMP_LT(rnp->gp_seq, rnp->gp_seq_needed)) {
@ -2055,12 +2049,14 @@ static void rcu_gp_cleanup(void)
}
/* Advance CBs to reduce false positives below. */
if (!rcu_accelerate_cbs(rnp, rdp) && needgp) {
WRITE_ONCE(rsp->gp_flags, RCU_GP_FLAG_INIT);
rsp->gp_req_activity = jiffies;
trace_rcu_grace_period(rsp->name, READ_ONCE(rsp->gp_seq),
WRITE_ONCE(rcu_state.gp_flags, RCU_GP_FLAG_INIT);
rcu_state.gp_req_activity = jiffies;
trace_rcu_grace_period(rcu_state.name,
READ_ONCE(rcu_state.gp_seq),
TPS("newreq"));
} else {
WRITE_ONCE(rsp->gp_flags, rsp->gp_flags & RCU_GP_FLAG_INIT);
WRITE_ONCE(rcu_state.gp_flags,
rcu_state.gp_flags & RCU_GP_FLAG_INIT);
}
raw_spin_unlock_irq_rcu_node(rnp);
}
@ -2074,7 +2070,6 @@ static int __noreturn rcu_gp_kthread(void *unused)
int gf;
unsigned long j;
int ret;
struct rcu_state *rsp = &rcu_state;
struct rcu_node *rnp = rcu_get_root();
rcu_bind_gp_kthread();
@ -2082,21 +2077,22 @@ static int __noreturn rcu_gp_kthread(void *unused)
/* Handle grace-period start. */
for (;;) {
trace_rcu_grace_period(rsp->name,
READ_ONCE(rsp->gp_seq),
trace_rcu_grace_period(rcu_state.name,
READ_ONCE(rcu_state.gp_seq),
TPS("reqwait"));
rsp->gp_state = RCU_GP_WAIT_GPS;
swait_event_idle_exclusive(rsp->gp_wq, READ_ONCE(rsp->gp_flags) &
rcu_state.gp_state = RCU_GP_WAIT_GPS;
swait_event_idle_exclusive(rcu_state.gp_wq,
READ_ONCE(rcu_state.gp_flags) &
RCU_GP_FLAG_INIT);
rsp->gp_state = RCU_GP_DONE_GPS;
rcu_state.gp_state = RCU_GP_DONE_GPS;
/* Locking provides needed memory barrier. */
if (rcu_gp_init())
break;
cond_resched_tasks_rcu_qs();
WRITE_ONCE(rsp->gp_activity, jiffies);
WRITE_ONCE(rcu_state.gp_activity, jiffies);
WARN_ON(signal_pending(current));
trace_rcu_grace_period(rsp->name,
READ_ONCE(rsp->gp_seq),
trace_rcu_grace_period(rcu_state.name,
READ_ONCE(rcu_state.gp_seq),
TPS("reqwaitsig"));
}
@ -2106,58 +2102,59 @@ static int __noreturn rcu_gp_kthread(void *unused)
ret = 0;
for (;;) {
if (!ret) {
rsp->jiffies_force_qs = jiffies + j;
WRITE_ONCE(rsp->jiffies_kick_kthreads,
rcu_state.jiffies_force_qs = jiffies + j;
WRITE_ONCE(rcu_state.jiffies_kick_kthreads,
jiffies + 3 * j);
}
trace_rcu_grace_period(rsp->name,
READ_ONCE(rsp->gp_seq),
trace_rcu_grace_period(rcu_state.name,
READ_ONCE(rcu_state.gp_seq),
TPS("fqswait"));
rsp->gp_state = RCU_GP_WAIT_FQS;
ret = swait_event_idle_timeout_exclusive(rsp->gp_wq,
rcu_state.gp_state = RCU_GP_WAIT_FQS;
ret = swait_event_idle_timeout_exclusive(rcu_state.gp_wq,
rcu_gp_fqs_check_wake(&gf), j);
rsp->gp_state = RCU_GP_DOING_FQS;
rcu_state.gp_state = RCU_GP_DOING_FQS;
/* Locking provides needed memory barriers. */
/* If grace period done, leave loop. */
if (!READ_ONCE(rnp->qsmask) &&
!rcu_preempt_blocked_readers_cgp(rnp))
break;
/* If time for quiescent-state forcing, do it. */
if (ULONG_CMP_GE(jiffies, rsp->jiffies_force_qs) ||
if (ULONG_CMP_GE(jiffies, rcu_state.jiffies_force_qs) ||
(gf & RCU_GP_FLAG_FQS)) {
trace_rcu_grace_period(rsp->name,
READ_ONCE(rsp->gp_seq),
trace_rcu_grace_period(rcu_state.name,
READ_ONCE(rcu_state.gp_seq),
TPS("fqsstart"));
rcu_gp_fqs(first_gp_fqs);
first_gp_fqs = false;
trace_rcu_grace_period(rsp->name,
READ_ONCE(rsp->gp_seq),
trace_rcu_grace_period(rcu_state.name,
READ_ONCE(rcu_state.gp_seq),
TPS("fqsend"));
cond_resched_tasks_rcu_qs();
WRITE_ONCE(rsp->gp_activity, jiffies);
WRITE_ONCE(rcu_state.gp_activity, jiffies);
ret = 0; /* Force full wait till next FQS. */
j = jiffies_till_next_fqs;
} else {
/* Deal with stray signal. */
cond_resched_tasks_rcu_qs();
WRITE_ONCE(rsp->gp_activity, jiffies);
WRITE_ONCE(rcu_state.gp_activity, jiffies);
WARN_ON(signal_pending(current));
trace_rcu_grace_period(rsp->name,
READ_ONCE(rsp->gp_seq),
trace_rcu_grace_period(rcu_state.name,
READ_ONCE(rcu_state.gp_seq),
TPS("fqswaitsig"));
ret = 1; /* Keep old FQS timing. */
j = jiffies;
if (time_after(jiffies, rsp->jiffies_force_qs))
if (time_after(jiffies,
rcu_state.jiffies_force_qs))
j = 1;
else
j = rsp->jiffies_force_qs - j;
j = rcu_state.jiffies_force_qs - j;
}
}
/* Handle grace-period end. */
rsp->gp_state = RCU_GP_CLEANUP;
rcu_state.gp_state = RCU_GP_CLEANUP;
rcu_gp_cleanup();
rsp->gp_state = RCU_GP_CLEANED;
rcu_state.gp_state = RCU_GP_CLEANED;
}
}
@ -2173,11 +2170,10 @@ static int __noreturn rcu_gp_kthread(void *unused)
static void rcu_report_qs_rsp(unsigned long flags)
__releases(rcu_get_root()->lock)
{
struct rcu_state *rsp = &rcu_state;
raw_lockdep_assert_held_rcu_node(rcu_get_root());
WARN_ON_ONCE(!rcu_gp_in_progress());
WRITE_ONCE(rsp->gp_flags, READ_ONCE(rsp->gp_flags) | RCU_GP_FLAG_FQS);
WRITE_ONCE(rcu_state.gp_flags,
READ_ONCE(rcu_state.gp_flags) | RCU_GP_FLAG_FQS);
raw_spin_unlock_irqrestore_rcu_node(rcu_get_root(), flags);
rcu_gp_kthread_wake();
}