proc: cleanup/simplify get_task_state/task_state_array

get_task_state() and task_state_array[] look confusing and suboptimal, it
is not clear what it can actually report to user-space and
task_state_array[] blows .data for no reason.

1. state = (tsk->state & TASK_REPORT) | tsk->exit_state is not
   clear. TASK_REPORT is self-documenting but it is not clear
   what ->exit_state can add.

   Move the potential exit_state's (EXIT_ZOMBIE and EXIT_DEAD)
   into TASK_REPORT and use it to calculate the final result.

2. With the change above it is obvious that task_state_array[]
   has the unused entries just to make BUILD_BUG_ON() happy.

   Change this BUILD_BUG_ON() to use TASK_REPORT rather than
   TASK_STATE_MAX and shrink task_state_array[].

3. Turn the "while (state)" loop into fls(state).

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: David Laight <David.Laight@ACULAB.COM>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 12 deletions

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 1bd2077187fd..554a0b229ac2 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -140,24 +140,15 @@ static const char * const task_state_array[] = {
         "t (tracing stop)",     /*   8 */
         "Z (zombie)",           /*  16 */
         "X (dead)",             /*  32 */
-        "x (dead)",             /*  64 */
-        "K (wakekill)",         /* 128 */
-        "W (waking)",           /* 256 */
-        "P (parked)",           /* 512 */
 };
 
 static inline const char *get_task_state(struct task_struct *tsk)
 {
-        unsigned int state = (tsk->state & TASK_REPORT) | tsk->exit_state;
-        const char * const *p = &task_state_array[0];
+        unsigned int state = (tsk->state | tsk->exit_state) & TASK_REPORT;
 
-        BUILD_BUG_ON(1 + ilog2(TASK_STATE_MAX) != ARRAY_SIZE(task_state_array));
+        BUILD_BUG_ON(1 + ilog2(TASK_REPORT) != ARRAY_SIZE(task_state_array)-1);
 
-        while (state) {
-                p++;
-                state >>= 1;
-        }
-        return *p;
+        return task_state_array[fls(state)];
 }
 
 static inline void task_state(struct seq_file *m, struct pid_namespace *ns,