FAILED: patch "[PATCH] sched, trace: Fix prev_state output in sched_switch" failed to apply to 4.14-stable tree

The patch below does not apply to the 4.14-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From: Pavankumar Kondeti <[email protected]>
Date: Tue, 30 Oct 2018 12:24:33 +0530
Subject: [PATCH] sched, trace: Fix prev_state output in sched_switch
tracepoint

commit 3f5fe9fef5b2 ("sched/debug: Fix task state recording/printout") tried to fix the problem introduced by a previous commit efb40f588b43 ("sched/tracing: Fix trace_sched_switch task-state printing"). However the prev_state output in sched_switch is still broken.

task_state_index() uses fls() which considers the LSB as 1. Left shifting 1 by this value gives an incorrect mapping to the task state. Fix this by decrementing the value returned by __get_task_state() before shifting.

index f07b270d4fc4..9a4bdfadab07 100644
@@ -107,6 +107,8 @@ DEFINE_EVENT(sched_wakeup_template, sched_wakeup_new,
 #ifdef CREATE_TRACE_POINTS
 static inline long __trace_sched_switch_state(bool preempt, struct task_struct *p)
 {
+	unsigned int state;
+
 #ifdef CONFIG_SCHED_DEBUG
 	BUG_ON(p != current);
 #endif /* CONFIG_SCHED_DEBUG */

@@ -118,7 +120,15 @@ static inline long __trace_sched_switch_state(bool preempt, struct task_struct *
 	if (preempt)
 		return TASK_REPORT_MAX;
 
-	return 1 << task_state_index(p);
+	/*
+	 * task_state_index() uses fls() and returns a value from 0-8 range.
+	 * Decrement it by 1 (except TASK_RUNNING state i.e 0) before using
+	 * it for left shift operation to get the correct task->state
+	 * mapping.
+	 */
+	state = task_state_index(p);
+
+	return state ? (1 << (state - 1)) : state;
 }
 #endif /* CREATE_TRACE_POINTS */