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Subject[PATCH 3/5] sched: save a previous state on task_struct
Date
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@openvz.org>
---
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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