[PATCH 1/8] sched: Consistent task-state printing

[Peter Zijlstra]

Currently get_task_state() and task_state_to_char() report different
states, create a number of common helpers and unify the reported state
space.

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
 fs/proc/array.c       |   15 ++-------------
 include/linux/sched.h |   26 +++++++++++++++++++-------
 2 files changed, 21 insertions(+), 20 deletions(-)

--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -129,19 +129,8 @@ static const char * const task_state_arr
 
 static inline const char *get_task_state(struct task_struct *tsk)
 {
-	unsigned int state = (tsk->state | tsk->exit_state) & TASK_REPORT;
-
-	/*
-	 * Parked tasks do not run; they sit in __kthread_parkme().
-	 * Without this check, we would report them as running, which is
-	 * clearly wrong, so we report them as sleeping instead.
-	 */
-	if (tsk->state == TASK_PARKED)
-		state = TASK_INTERRUPTIBLE;
-
-	BUILD_BUG_ON(1 + ilog2(TASK_REPORT) != ARRAY_SIZE(task_state_array)-1);
-
-	return task_state_array[fls(state)];
+	BUILD_BUG_ON(1 + ilog2(TASK_REPORT) != ARRAY_SIZE(task_state_array) - 1);
+	return task_state_array[__get_task_state(tsk)];
 }
 
 static inline int get_task_umask(struct task_struct *tsk)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1244,17 +1244,29 @@ static inline pid_t task_pgrp_nr(struct
 	return task_pgrp_nr_ns(tsk, &init_pid_ns);
 }
 
-static inline char task_state_to_char(struct task_struct *task)
+static inline unsigned int __get_task_state(struct task_struct *tsk)
 {
-	const char stat_nam[] = TASK_STATE_TO_CHAR_STR;
-	unsigned long state = task->state;
+	unsigned int tsk_state = READ_ONCE(tsk->state);
+	unsigned int state = (tsk_state | tsk->exit_state) & TASK_REPORT;
 
-	state = state ? __ffs(state) + 1 : 0;
+	if (tsk_state == TASK_PARKED)
+		state = TASK_INTERRUPTIBLE;
 
-	/* Make sure the string lines up properly with the number of task states: */
-	BUILD_BUG_ON(sizeof(TASK_STATE_TO_CHAR_STR)-1 != ilog2(TASK_STATE_MAX)+1);
+	return fls(state);
+}
+
+static inline char __task_state_to_char(unsigned int state)
+{
+	static const char state_char[] = "RSDTtXZ";
+
+	BUILD_BUG_ON(1 + ilog2(TASK_REPORT) != sizeof(state_char) - 2);
 
-	return state < sizeof(stat_nam) - 1 ? stat_nam[state] : '?';
+	return state_char[state];
+}
+
+static inline char task_state_to_char(struct task_struct *tsk)
+{
+	return __task_state_to_char(__get_task_state(tsk));
 }
 
 /**