linux-kernel - [PATCH] sched/tracing: Fix task state recording/printout

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Date:   Wed, 22 Nov 2017 13:05:48 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
cc:     Steven Rostedt <rostedt@...dmis.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH] sched/tracing: Fix task state recording/printout

The recent conversion of the task state recording to use task_state_index()
broke the sched_switch tracepoint task state output.

task_state_index() returns surprisingly an index (0-7) which is then
printed with __print_flags() applying bitmasks. Not really working and
resulting in weird states like 'prev_state=t' instead of 'prev_state=I'.

Use TASK_REPORT_MAX instead of TASK_STATE_MAX to report preemption. Build a
bitmask from the return value of task_state_index() and store it in
entry->prev_state, which makes __print_flags() work as expected.

Fixes: efb40f588b43 ("sched/tracing: Fix trace_sched_switch task-state printing")
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: stable@...r.kernel.org
---
 include/trace/events/sched.h |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -116,9 +116,9 @@ static inline long __trace_sched_switch_
 	 * RUNNING (we will not have dequeued if state != RUNNING).
 	 */
 	if (preempt)
-		return TASK_STATE_MAX;
+		return TASK_REPORT_MAX;
 
-	return task_state_index(p);
+	return 1 << task_state_index(p);
 }
 #endif /* CREATE_TRACE_POINTS */
 
@@ -164,7 +164,7 @@ TRACE_EVENT(sched_switch,
 				{ 0x40, "P" }, { 0x80, "I" }) :
 		  "R",
 
-		__entry->prev_state & TASK_STATE_MAX ? "+" : "",
+		__entry->prev_state & TASK_REPORT_MAX ? "+" : "",
 		__entry->next_comm, __entry->next_pid, __entry->next_prio)
 );