[PATCH 14/20] rcu/context_tracking: Move dynticks_nmi_nesting to context tracking

Frederic Weisbecker
2022-06-28T13:18:38Z

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.

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>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Tested-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
---
include/linux/context_tracking_state.h | 16 +++++++++
kernel/context_tracking.c | 1 +
kernel/rcu/rcu.h | 4 ---
kernel/rcu/tree.c | 48 +++++++++++---------------
kernel/rcu/tree.h | 1 -
kernel/rcu/tree_stall.h | 2 +-
6 files changed, 39 insertions(+), 33 deletions(-)

diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h
index 13a4a9d1ec7e..5f11e3d2d85a 100644
--- a/include/linux/context_tracking_state.h
+++ b/include/linux/context_tracking_state.h
@@ -13,6 +13,9 @@ enum ctx_state {
CONTEXT_GUEST,
};

+/* Offset to allow distinguishing irq vs. task-based idle entry/exit. */
+#define DYNTICK_IRQ_NONIDLE ((LONG_MAX / 2) + 1)
+
struct context_tracking {
#ifdef CONFIG_CONTEXT_TRACKING_USER
/*
@@ -28,6 +31,7 @@ struct context_tracking {
#ifdef CONFIG_CONTEXT_TRACKING_IDLE
atomic_t dynticks; /* Even value for idle, else odd. */
long dynticks_nesting; /* Track process nesting level. */
+ long dynticks_nmi_nesting; /* Track irq/NMI nesting level. */
#endif
};

@@ -66,6 +70,18 @@ static __always_inline long ct_dynticks_nesting_cpu(int cpu)

return ct->dynticks_nesting;
}
+
+static __always_inline long ct_dynticks_nmi_nesting(void)
+{
+ return __this_cpu_read(context_tracking.dynticks_nmi_nesting);
+}
+
+static __always_inline long ct_dynticks_nmi_nesting_cpu(int cpu)
+{
+ struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
+
+ return ct->dynticks_nmi_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 dfefe04400f8..7c3033e9a518 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -26,6 +26,7 @@
DEFINE_PER_CPU(struct context_tracking, context_tracking) = {
#ifdef CONFIG_CONTEXT_TRACKING_IDLE
.dynticks_nesting = 1,
+ .dynticks_nmi_nesting = DYNTICK_IRQ_NONIDLE,
.dynticks = ATOMIC_INIT(1),
#endif
};
diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index 4916077119f3..7b4a88deff9a 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -12,10 +12,6 @@

#include <trace/events/rcu.h>

-/* Offset to allow distinguishing irq vs. task-based idle entry/exit. */
-#define DYNTICK_IRQ_NONIDLE ((LONG_MAX / 2) + 1)
-
-
/*
* Grace-period counter management.
*/
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index f6bf328bb9cf..006939b29e82 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_nmi_nesting = DYNTICK_IRQ_NONIDLE,
#ifdef CONFIG_RCU_NOCB_CPU
.cblist.flags = SEGCBLIST_RCU_CORE,
#endif
@@ -437,11 +436,11 @@ static int rcu_is_cpu_rrupt_from_idle(void)
/* Check for counter underflows */
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_LOCKDEP_WARN(ct_dynticks_nmi_nesting() <= 0,
"RCU dynticks_nmi_nesting counter underflow/zero!");

/* Are we at first interrupt nesting level? */
- nesting = __this_cpu_read(rcu_data.dynticks_nmi_nesting);
+ nesting = ct_dynticks_nmi_nesting();
if (nesting > 1)
return false;

@@ -612,11 +611,10 @@ EXPORT_SYMBOL_GPL(rcutorture_get_gp_data);
*/
static noinstr void rcu_eqs_enter(bool user)
{
- struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
struct context_tracking *ct = this_cpu_ptr(&context_tracking);

- WARN_ON_ONCE(rdp->dynticks_nmi_nesting != DYNTICK_IRQ_NONIDLE);
- WRITE_ONCE(rdp->dynticks_nmi_nesting, 0);
+ WARN_ON_ONCE(ct_dynticks_nmi_nesting() != DYNTICK_IRQ_NONIDLE);
+ WRITE_ONCE(ct->dynticks_nmi_nesting, 0);
WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
ct_dynticks_nesting() == 0);
if (ct_dynticks_nesting() != 1) {
@@ -734,7 +732,7 @@ noinstr void rcu_user_enter(void)
* rcu_nmi_exit - inform RCU of exit from NMI context
*
* If we are returning from the outermost NMI handler that interrupted an
- * RCU-idle period, update ct->dynticks and rdp->dynticks_nmi_nesting
+ * RCU-idle period, update ct->dynticks and ct->dynticks_nmi_nesting
* to let the RCU grace-period handling know that the CPU is back to
* being RCU-idle.
*
@@ -744,7 +742,6 @@ noinstr void rcu_user_enter(void)
noinstr void rcu_nmi_exit(void)
{
struct context_tracking *ct = this_cpu_ptr(&context_tracking);
- struct rcu_data *rdp = this_cpu_ptr(&rcu_data);

instrumentation_begin();
/*
@@ -752,25 +749,25 @@ noinstr void rcu_nmi_exit(void)
* (We are exiting an NMI handler, so RCU better be paying attention
* to us!)
*/
- WARN_ON_ONCE(rdp->dynticks_nmi_nesting <= 0);
+ WARN_ON_ONCE(ct_dynticks_nmi_nesting() <= 0);
WARN_ON_ONCE(rcu_dynticks_curr_cpu_in_eqs());

/*
* If the nesting level is not 1, the CPU wasn't RCU-idle, so
* leave it in non-RCU-idle state.
*/
- if (rdp->dynticks_nmi_nesting != 1) {
- trace_rcu_dyntick(TPS("--="), rdp->dynticks_nmi_nesting, rdp->dynticks_nmi_nesting - 2,
+ if (ct_dynticks_nmi_nesting() != 1) {
+ trace_rcu_dyntick(TPS("--="), ct_dynticks_nmi_nesting(), ct_dynticks_nmi_nesting() - 2,
ct_dynticks());
- WRITE_ONCE(rdp->dynticks_nmi_nesting, /* No store tearing. */
- rdp->dynticks_nmi_nesting - 2);
+ WRITE_ONCE(ct->dynticks_nmi_nesting, /* No store tearing. */
+ ct_dynticks_nmi_nesting() - 2);
instrumentation_end();
return;
}

/* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */
- trace_rcu_dyntick(TPS("Startirq"), rdp->dynticks_nmi_nesting, 0, ct_dynticks());
- WRITE_ONCE(rdp->dynticks_nmi_nesting, 0); /* Avoid store tearing. */
+ trace_rcu_dyntick(TPS("Startirq"), ct_dynticks_nmi_nesting(), 0, ct_dynticks());
+ WRITE_ONCE(ct->dynticks_nmi_nesting, 0); /* Avoid store tearing. */

// instrumentation for the noinstr rcu_dynticks_eqs_enter()
instrument_atomic_write(&ct->dynticks, sizeof(ct->dynticks));
@@ -794,7 +791,7 @@ void rcu_irq_exit_check_preempt(void)

RCU_LOCKDEP_WARN(ct_dynticks_nesting() <= 0,
"RCU dynticks_nesting counter underflow/zero!");
- RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nmi_nesting) !=
+ RCU_LOCKDEP_WARN(ct_dynticks_nmi_nesting() !=
DYNTICK_IRQ_NONIDLE,
"Bad RCU dynticks_nmi_nesting counter\n");
RCU_LOCKDEP_WARN(rcu_dynticks_curr_cpu_in_eqs(),
@@ -813,11 +810,9 @@ void rcu_irq_exit_check_preempt(void)
static void noinstr rcu_eqs_exit(bool user)
{
struct context_tracking *ct = this_cpu_ptr(&context_tracking);
- struct rcu_data *rdp;
long oldval;

WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !raw_irqs_disabled());
- rdp = this_cpu_ptr(&rcu_data);
oldval = ct_dynticks_nesting();
WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && oldval < 0);
if (oldval) {
@@ -837,8 +832,8 @@ static void noinstr rcu_eqs_exit(bool user)
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(ct->dynticks_nesting, 1);
- WARN_ON_ONCE(rdp->dynticks_nmi_nesting);
- WRITE_ONCE(rdp->dynticks_nmi_nesting, DYNTICK_IRQ_NONIDLE);
+ WARN_ON_ONCE(ct_dynticks_nmi_nesting());
+ WRITE_ONCE(ct->dynticks_nmi_nesting, DYNTICK_IRQ_NONIDLE);
instrumentation_end();
}

@@ -941,7 +936,7 @@ void __rcu_irq_enter_check_tick(void)
* rcu_nmi_enter - inform RCU of entry to NMI context
*
* If the CPU was idle from RCU's viewpoint, update ct->dynticks and
- * rdp->dynticks_nmi_nesting to let the RCU grace-period handling know
+ * ct->dynticks_nmi_nesting to let the RCU grace-period handling know
* that the CPU is active. This implementation permits nested NMIs, as
* long as the nesting level does not overflow an int. (You will probably
* run out of stack space first.)
@@ -952,11 +947,10 @@ void __rcu_irq_enter_check_tick(void)
noinstr void rcu_nmi_enter(void)
{
long incby = 2;
- struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
struct context_tracking *ct = this_cpu_ptr(&context_tracking);

/* Complain about underflow. */
- WARN_ON_ONCE(rdp->dynticks_nmi_nesting < 0);
+ WARN_ON_ONCE(ct_dynticks_nmi_nesting() < 0);

/*
* If idle from RCU viewpoint, atomically increment ->dynticks
@@ -990,11 +984,11 @@ noinstr void rcu_nmi_enter(void)
}

trace_rcu_dyntick(incby == 1 ? TPS("Endirq") : TPS("++="),
- rdp->dynticks_nmi_nesting,
- rdp->dynticks_nmi_nesting + incby, ct_dynticks());
+ ct_dynticks_nmi_nesting(),
+ ct_dynticks_nmi_nesting() + incby, ct_dynticks());
instrumentation_end();
- WRITE_ONCE(rdp->dynticks_nmi_nesting, /* Prevent store tearing. */
- rdp->dynticks_nmi_nesting + incby);
+ WRITE_ONCE(ct->dynticks_nmi_nesting, /* Prevent store tearing. */
+ ct_dynticks_nmi_nesting() + incby);
barrier();
}

diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index 650ff3cf0121..72dbf8512ce7 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -187,7 +187,6 @@ struct rcu_data {

/* 3) dynticks interface. */
int dynticks_snap; /* Per-GP tracking for dynticks. */
- 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. */
bool rcu_forced_tick; /* Forced tick to provide QS. */
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index a9c82254b6c6..2683ce0a7c72 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,
- ct_dynticks_nesting_cpu(cpu), rdp->dynticks_nmi_nesting,
+ ct_dynticks_nesting_cpu(cpu), ct_dynticks_nmi_nesting_cpu(cpu),
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