[RFC PATCH 03/11] sched: Add sched tracepoints for RV task model

[Gabriele Monaco]

Add the following tracepoints:
* sched_entry(bool preempt, ip)
    Called while entering __schedule
* sched_exit(bool is_switch, ip)
    Called while exiting __schedule
* sched_set_need_resched(task)
    Called when we set the need for reschedule
* sched_set_state(task, curr_state, state)
    Called when a task changes its state (to and from running)

These tracepoints are useful to describe the Linux task model and are
adapted from the patches by Daniel Bristot de Oliveira
(https://bristot.me/linux-task-model/).

Signed-off-by: Gabriele Monaco <gmonaco@xxxxxxxxxx>
---
 include/linux/rv.h                 |  2 +-
 include/linux/sched.h              |  7 +++++++
 include/trace/events/sched.h       | 17 +++++++++++++++++
 kernel/sched/core.c                | 21 ++++++++++++++++++++-
 tools/verification/rv/include/rv.h |  2 +-
 5 files changed, 46 insertions(+), 3 deletions(-)

diff --git a/include/linux/rv.h b/include/linux/rv.h
index 8883b41d88ec4..55d458be53a4c 100644
--- a/include/linux/rv.h
+++ b/include/linux/rv.h
@@ -7,7 +7,7 @@
 #ifndef _LINUX_RV_H
 #define _LINUX_RV_H
 
-#define MAX_DA_NAME_LEN	24
+#define MAX_DA_NAME_LEN	32
 
 #ifdef CONFIG_RV
 /*
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 9632e3318e0d6..af9fa18035c71 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -226,12 +226,14 @@ struct user_event_mm;
 #define __set_current_state(state_value)				\
 	do {								\
 		debug_normal_state_change((state_value));		\
+		trace_set_current_state(state_value);			\
 		WRITE_ONCE(current->__state, (state_value));		\
 	} while (0)
 
 #define set_current_state(state_value)					\
 	do {								\
 		debug_normal_state_change((state_value));		\
+		trace_set_current_state(state_value);			\
 		smp_store_mb(current->__state, (state_value));		\
 	} while (0)
 
@@ -247,6 +249,7 @@ struct user_event_mm;
 									\
 		raw_spin_lock_irqsave(&current->pi_lock, flags);	\
 		debug_special_state_change((state_value));		\
+		trace_set_current_state(state_value);			\
 		WRITE_ONCE(current->__state, (state_value));		\
 		raw_spin_unlock_irqrestore(&current->pi_lock, flags);	\
 	} while (0)
@@ -282,6 +285,7 @@ struct user_event_mm;
 		raw_spin_lock(&current->pi_lock);			\
 		current->saved_state = current->__state;		\
 		debug_rtlock_wait_set_state();				\
+		trace_set_current_state(TASK_RTLOCK_WAIT);		\
 		WRITE_ONCE(current->__state, TASK_RTLOCK_WAIT);		\
 		raw_spin_unlock(&current->pi_lock);			\
 	} while (0);
@@ -291,6 +295,7 @@ struct user_event_mm;
 		lockdep_assert_irqs_disabled();				\
 		raw_spin_lock(&current->pi_lock);			\
 		debug_rtlock_wait_restore_state();			\
+		trace_set_current_state(TASK_RUNNING);			\
 		WRITE_ONCE(current->__state, current->saved_state);	\
 		current->saved_state = TASK_RUNNING;			\
 		raw_spin_unlock(&current->pi_lock);			\
@@ -327,6 +332,8 @@ extern void io_schedule_finish(int token);
 extern long io_schedule_timeout(long timeout);
 extern void io_schedule(void);
 
+extern void trace_set_current_state(int state_value);
+
 /**
  * struct prev_cputime - snapshot of system and user cputime
  * @utime: time spent in user mode
diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index 9ea4c404bd4ef..1ac0e23b0733d 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -824,6 +824,23 @@ DECLARE_TRACE(sched_compute_energy_tp,
 		 unsigned long max_util, unsigned long busy_time),
 	TP_ARGS(p, dst_cpu, energy, max_util, busy_time));
 
+DECLARE_TRACE(sched_entry_tp,
+	TP_PROTO(bool preempt, unsigned long ip),
+	TP_ARGS(preempt, ip));
+
+DECLARE_TRACE(sched_exit_tp,
+	TP_PROTO(bool is_switch, unsigned long ip),
+	TP_ARGS(is_switch, ip));
+
+DECLARE_TRACE(sched_set_need_resched_tp,
+	TP_PROTO(struct task_struct *tsk),
+	TP_ARGS(tsk));
+
+DECLARE_TRACE_CONDITION(sched_set_state_tp,
+	TP_PROTO(struct task_struct *tsk, int curr_state, int state),
+	TP_ARGS(tsk, curr_state, state),
+	TP_CONDITION(!!curr_state != !!state));
+
 #endif /* _TRACE_SCHED_H */
 
 /* This part must be outside protection */
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 165c90ba64ea9..fb5f8aa61ef5d 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -491,6 +491,12 @@ sched_core_dequeue(struct rq *rq, struct task_struct *p, int flags) { }
 
 #endif /* CONFIG_SCHED_CORE */
 
+void trace_set_current_state(int state_value)
+{
+	trace_sched_set_state_tp(current, current->__state, state_value);
+}
+EXPORT_SYMBOL(trace_set_current_state);
+
 /*
  * Serialization rules:
  *
@@ -1103,6 +1109,8 @@ static void __resched_curr(struct rq *rq, int tif)
 
 	cpu = cpu_of(rq);
 
+	trace_sched_set_need_resched_tp(curr);
+
 	if (cpu == smp_processor_id()) {
 		set_ti_thread_flag(cti, tif);
 		if (tif == TIF_NEED_RESCHED)
@@ -5306,6 +5314,12 @@ asmlinkage __visible void schedule_tail(struct task_struct *prev)
 	 */
 
 	finish_task_switch(prev);
+	/*
+	 * This is a special case: the newly created task has just
+	 * switched the context for the fist time. It is returning from
+	 * schedule for the first time in this path.
+	 */
+	trace_sched_exit_tp(true, CALLER_ADDR0);
 	preempt_enable();
 
 	if (current->set_child_tid)
@@ -6649,12 +6663,15 @@ static void __sched notrace __schedule(int sched_mode)
 	 * as a preemption by schedule_debug() and RCU.
 	 */
 	bool preempt = sched_mode > SM_NONE;
+	bool is_switch = false;
 	unsigned long *switch_count;
 	unsigned long prev_state;
 	struct rq_flags rf;
 	struct rq *rq;
 	int cpu;
 
+	trace_sched_entry_tp(preempt, CALLER_ADDR0);
+
 	cpu = smp_processor_id();
 	rq = cpu_rq(cpu);
 	prev = rq->curr;
@@ -6722,7 +6739,8 @@ static void __sched notrace __schedule(int sched_mode)
 	rq->last_seen_need_resched_ns = 0;
 #endif
 
-	if (likely(prev != next)) {
+	is_switch = prev != next;
+	if (likely(is_switch)) {
 		rq->nr_switches++;
 		/*
 		 * RCU users of rcu_dereference(rq->curr) may not see
@@ -6767,6 +6785,7 @@ static void __sched notrace __schedule(int sched_mode)
 		__balance_callbacks(rq);
 		raw_spin_rq_unlock_irq(rq);
 	}
+	trace_sched_exit_tp(is_switch, CALLER_ADDR0);
 }
 
 void __noreturn do_task_dead(void)
diff --git a/tools/verification/rv/include/rv.h b/tools/verification/rv/include/rv.h
index 770fd6da36107..0cab1037a98f7 100644
--- a/tools/verification/rv/include/rv.h
+++ b/tools/verification/rv/include/rv.h
@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 
 #define MAX_DESCRIPTION 1024
-#define MAX_DA_NAME_LEN	24
+#define MAX_DA_NAME_LEN	32
 
 struct monitor {
 	char name[MAX_DA_NAME_LEN];
-- 
2.48.1