[PATCH 3/5] sched: save a previous state on task_struct

[Andrew Vagin]

prev_state is a state of task, when it stops executing on cpu.

It's needed for filtering sched:sched_switch_finish.
For example If we want to track when a task is sleeping:

./perf record -e sched:sched_switch -g --filter 'prev_state == 1' \
	-e sched:sched_switch_finish --filter 'state == 1' -P  foo

The previous state is set in sched:sched_switch, so it works when
both events sched:sched_switch and sched:sched_switch_finish are
enabled.

Signed-off-by: Andrew Vagin <avagin@xxxxxxxxxx>
---
 include/linux/sched.h        |    3 +++
 include/trace/events/sched.h |   12 +++++++++++-
 2 files changed, 14 insertions(+), 1 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index f45c0b2..172bbe3 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1576,6 +1576,9 @@ struct task_struct {
 	struct uprobe_task *utask;
 	int uprobe_srcu_id;
 #endif
+#ifdef CONFIG_EVENT_TRACING
+	volatile long prev_state;
+#endif
 };
 
 /* Future-safe accessor for struct task_struct's cpus_allowed. */
diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index b2219d8..c1b70b1 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -133,6 +133,7 @@ TRACE_EVENT(sched_switch,
 		__entry->prev_pid	= prev->pid;
 		__entry->prev_prio	= prev->prio;
 		__entry->prev_state	= __trace_sched_switch_state(prev);
+		prev->prev_state	= __trace_sched_switch_state(prev);
 		memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
 		__entry->next_pid	= next->pid;
 		__entry->next_prio	= next->prio;
@@ -158,14 +159,23 @@ TRACE_EVENT(sched_switch_finish,
 	TP_STRUCT__entry(
 		__array(	char,	comm,	TASK_COMM_LEN	)
 		__field(	pid_t,	pid			)
+		__field(	long,	state			)
 	),
 
 	TP_fast_assign(
 		__entry->pid	= p->pid;
+		__entry->state	= p->prev_state;
 		memcpy(__entry->comm, p->comm, TASK_COMM_LEN);
 	),
 
-	TP_printk("comm=%s pid=%d", __entry->comm, __entry->pid)
+	TP_printk("comm=%s pid=%d state=%s%s",
+		__entry->comm, __entry->pid,
+		__entry->state & (TASK_STATE_MAX-1) ?
+		  __print_flags(__entry->state & (TASK_STATE_MAX-1), "|",
+				{ 1, "S"} , { 2, "D" }, { 4, "T" }, { 8, "t" },
+				{ 16, "Z" }, { 32, "X" }, { 64, "x" },
+				{ 128, "W" }) : "R",
+		__entry->state & TASK_STATE_MAX ? "+" : "")
 );
 
 /*
-- 
1.7.1

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