tracing: add previous task state info to sched switch event

It is useful to see the state of a task that is being switched out.
This patch adds the output of the state of the previous task in
the context switch event.

[ Impact: see state of switched out task in context switch ]

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

1 files changed, 8 insertions, 1 deletions

diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index dd4033cf5b09..24ab5bcff7b2 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -156,6 +156,7 @@ TRACE_EVENT(sched_switch,
                 __array(        char,   prev_comm,      TASK_COMM_LEN   )
                 __field(        pid_t,  prev_pid                        )
                 __field(        int,    prev_prio                       )
+                __field(        long,   prev_state                      )
                 __array(        char,   next_comm,      TASK_COMM_LEN   )
                 __field(        pid_t,  next_pid                        )
                 __field(        int,    next_prio                       )
@@ -165,13 +166,19 @@ TRACE_EVENT(sched_switch,
                 memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
                 __entry->prev_pid       = prev->pid;
                 __entry->prev_prio      = prev->prio;
+                __entry->prev_state     = prev->state;
                 memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
                 __entry->next_pid       = next->pid;
                 __entry->next_prio      = next->prio;
         ),
 
-        TP_printk("task %s:%d [%d] ==> %s:%d [%d]",
+        TP_printk("task %s:%d [%d] (%s) ==> %s:%d [%d]",
                 __entry->prev_comm, __entry->prev_pid, __entry->prev_prio,
+                __entry->prev_state ?
+                  __print_flags(__entry->prev_state, "|",
+                                { 1, "S"} , { 2, "D" }, { 4, "T" }, { 8, "t" },
+                                { 16, "Z" }, { 32, "X" }, { 64, "x" },
+                                { 128, "W" }) : "R",
                 __entry->next_comm, __entry->next_pid, __entry->next_prio)
 );