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Subject[PATCH 13/20] rcu/context_tracking: Move dynticks_nesting to context tracking
Date
The RCU eqs tracking is going to be performed by the context tracking
subsystem. The related nesting counters thus need to be moved to the
context tracking structure.

Acked-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Cc: Uladzislau Rezki <uladzislau.rezki@sony.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Nicolas Saenz Julienne <nsaenz@kernel.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Cc: Yu Liao<liaoyu15@huawei.com>
Cc: Phil Auld <pauld@redhat.com>
Cc: Paul Gortmaker<paul.gortmaker@windriver.com>
Cc: Alex Belits <abelits@marvell.com>
---
include/linux/context_tracking_state.h | 12 ++++++++++
kernel/context_tracking.c | 1 +
kernel/rcu/tree.c | 31 +++++++++++++-------------
kernel/rcu/tree.h | 1 -
kernel/rcu/tree_stall.h | 2 +-
5 files changed, 30 insertions(+), 17 deletions(-)

diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h
index 651bb9c353f0..164f4673ee74 100644
--- a/include/linux/context_tracking_state.h
+++ b/include/linux/context_tracking_state.h
@@ -25,6 +25,7 @@ struct context_tracking {
#endif
#ifdef CONFIG_CONTEXT_TRACKING_IDLE
atomic_t dynticks; /* Even value for idle, else odd. */
+ long dynticks_nesting; /* Track process nesting level. */
#endif
};

@@ -49,6 +50,17 @@ static __always_inline int ct_dynticks_cpu_acquire(int cpu)
struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
return atomic_read_acquire(&ct->dynticks);
}
+
+static __always_inline long ct_dynticks_nesting(void)
+{
+ return __this_cpu_read(context_tracking.dynticks_nesting);
+}
+
+static __always_inline long ct_dynticks_nesting_cpu(int cpu)
+{
+ struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
+ return ct->dynticks_nesting;
+}
#endif /* #ifdef CONFIG_CONTEXT_TRACKING_IDLE */

#ifdef CONFIG_CONTEXT_TRACKING_USER
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index 3475dbfa4d73..d5ff1de1a24a 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -25,6 +25,7 @@

DEFINE_PER_CPU(struct context_tracking, context_tracking) = {
#ifdef CONFIG_CONTEXT_TRACKING_IDLE
+ .dynticks_nesting = 1,
.dynticks = ATOMIC_INIT(1),
#endif
};
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 5c9ca5900540..5e7771c78162 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -75,7 +75,6 @@
/* Data structures. */

static DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, rcu_data) = {
- .dynticks_nesting = 1,
.dynticks_nmi_nesting = DYNTICK_IRQ_NONIDLE,
#ifdef CONFIG_RCU_NOCB_CPU
.cblist.flags = SEGCBLIST_RCU_CORE,
@@ -440,7 +439,7 @@ static int rcu_is_cpu_rrupt_from_idle(void)
lockdep_assert_irqs_disabled();

/* Check for counter underflows */
- RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nesting) < 0,
+ RCU_LOCKDEP_WARN(ct_dynticks_nesting() < 0,
"RCU dynticks_nesting counter underflow!");
RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nmi_nesting) <= 0,
"RCU dynticks_nmi_nesting counter underflow/zero!");
@@ -456,7 +455,7 @@ static int rcu_is_cpu_rrupt_from_idle(void)
WARN_ON_ONCE(!nesting && !is_idle_task(current));

/* Does CPU appear to be idle from an RCU standpoint? */
- return __this_cpu_read(rcu_data.dynticks_nesting) == 0;
+ return ct_dynticks_nesting() == 0;
}

#define DEFAULT_RCU_BLIMIT (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) ? 1000 : 10)
@@ -623,16 +622,16 @@ static noinstr void rcu_eqs_enter(bool user)
WARN_ON_ONCE(rdp->dynticks_nmi_nesting != DYNTICK_IRQ_NONIDLE);
WRITE_ONCE(rdp->dynticks_nmi_nesting, 0);
WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
- rdp->dynticks_nesting == 0);
- if (rdp->dynticks_nesting != 1) {
+ ct_dynticks_nesting() == 0);
+ if (ct_dynticks_nesting() != 1) {
// RCU will still be watching, so just do accounting and leave.
- rdp->dynticks_nesting--;
+ ct->dynticks_nesting--;
return;
}

instrumentation_begin();
lockdep_assert_irqs_disabled();
- trace_rcu_dyntick(TPS("Start"), rdp->dynticks_nesting, 0, ct_dynticks());
+ trace_rcu_dyntick(TPS("Start"), ct_dynticks_nesting(), 0, ct_dynticks());
WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
rcu_preempt_deferred_qs(current);

@@ -640,7 +639,7 @@ static noinstr void rcu_eqs_enter(bool user)
instrument_atomic_write(&ct->dynticks, sizeof(ct->dynticks));

instrumentation_end();
- WRITE_ONCE(rdp->dynticks_nesting, 0); /* Avoid irq-access tearing. */
+ WRITE_ONCE(ct->dynticks_nesting, 0); /* Avoid irq-access tearing. */
// RCU is watching here ...
rcu_dynticks_eqs_enter();
// ... but is no longer watching here.
@@ -797,7 +796,7 @@ void rcu_irq_exit_check_preempt(void)
{
lockdep_assert_irqs_disabled();

- RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nesting) <= 0,
+ RCU_LOCKDEP_WARN(ct_dynticks_nesting() <= 0,
"RCU dynticks_nesting counter underflow/zero!");
RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nmi_nesting) !=
DYNTICK_IRQ_NONIDLE,
@@ -823,11 +822,11 @@ static void noinstr rcu_eqs_exit(bool user)

WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !raw_irqs_disabled());
rdp = this_cpu_ptr(&rcu_data);
- oldval = rdp->dynticks_nesting;
+ oldval = ct_dynticks_nesting();
WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && oldval < 0);
if (oldval) {
// RCU was already watching, so just do accounting and leave.
- rdp->dynticks_nesting++;
+ ct->dynticks_nesting++;
return;
}
rcu_dynticks_task_exit();
@@ -839,9 +838,9 @@ static void noinstr rcu_eqs_exit(bool user)
// instrumentation for the noinstr rcu_dynticks_eqs_exit()
instrument_atomic_write(&ct->dynticks, sizeof(ct->dynticks));

- trace_rcu_dyntick(TPS("End"), rdp->dynticks_nesting, 1, ct_dynticks());
+ trace_rcu_dyntick(TPS("End"), ct_dynticks_nesting(), 1, ct_dynticks());
WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
- WRITE_ONCE(rdp->dynticks_nesting, 1);
+ WRITE_ONCE(ct->dynticks_nesting, 1);
WARN_ON_ONCE(rdp->dynticks_nmi_nesting);
WRITE_ONCE(rdp->dynticks_nmi_nesting, DYNTICK_IRQ_NONIDLE);
instrumentation_end();
@@ -4229,12 +4228,13 @@ static void rcu_init_new_rnp(struct rcu_node *rnp_leaf)
static void __init
rcu_boot_init_percpu_data(int cpu)
{
+ struct context_tracking *ct = this_cpu_ptr(&context_tracking);
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);

/* Set up local state, ensuring consistent view of global state. */
rdp->grpmask = leaf_node_cpu_bit(rdp->mynode, cpu);
INIT_WORK(&rdp->strict_work, strict_work_handler);
- WARN_ON_ONCE(rdp->dynticks_nesting != 1);
+ WARN_ON_ONCE(ct->dynticks_nesting != 1);
WARN_ON_ONCE(rcu_dynticks_in_eqs(rcu_dynticks_snap(cpu)));
rdp->barrier_seq_snap = rcu_state.barrier_sequence;
rdp->rcu_ofl_gp_seq = rcu_state.gp_seq;
@@ -4259,6 +4259,7 @@ rcu_boot_init_percpu_data(int cpu)
int rcutree_prepare_cpu(unsigned int cpu)
{
unsigned long flags;
+ struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
struct rcu_node *rnp = rcu_get_root();

@@ -4267,7 +4268,7 @@ int rcutree_prepare_cpu(unsigned int cpu)
rdp->qlen_last_fqs_check = 0;
rdp->n_force_qs_snap = READ_ONCE(rcu_state.n_force_qs);
rdp->blimit = blimit;
- rdp->dynticks_nesting = 1; /* CPU not up, no tearing. */
+ ct->dynticks_nesting = 1; /* CPU not up, no tearing. */
raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */

/*
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index 2e46ee108d13..642b11cd8027 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -191,7 +191,6 @@ struct rcu_data {

/* 3) dynticks interface. */
int dynticks_snap; /* Per-GP tracking for dynticks. */
- long dynticks_nesting; /* Track process nesting level. */
long dynticks_nmi_nesting; /* Track irq/NMI nesting level. */
bool rcu_need_heavy_qs; /* GP old, so heavy quiescent state! */
bool rcu_urgent_qs; /* GP old need light quiescent state. */
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index 594a3c5aded1..b5195bbd9ebc 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -479,7 +479,7 @@ static void print_cpu_stall_info(int cpu)
"!."[!delta],
ticks_value, ticks_title,
rcu_dynticks_snap(cpu) & 0xfff,
- rdp->dynticks_nesting, rdp->dynticks_nmi_nesting,
+ ct_dynticks_nesting_cpu(cpu), rdp->dynticks_nmi_nesting,
rdp->softirq_snap, kstat_softirqs_cpu(RCU_SOFTIRQ, cpu),
data_race(rcu_state.n_force_qs) - rcu_state.n_force_qs_gpstart,
rcuc_starved ? buf : "",
--
2.25.1
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