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>

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 1bd2077..554a0b2 100644 (file)
--- 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,

diff --git a/include/linux/sched.h b/include/linux/sched.h
index cf9e414..33e4e9e 100644 (file)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -229,7 +229,7 @@ extern char ___assert_task_state[1 - 2*!!(
 /* get_task_state() */
 #define TASK_REPORT            (TASK_RUNNING | TASK_INTERRUPTIBLE | \
                                 TASK_UNINTERRUPTIBLE | __TASK_STOPPED | \
-                                __TASK_TRACED)
+                                __TASK_TRACED | EXIT_ZOMBIE | EXIT_DEAD)
 
 #define task_is_traced(task)   ((task->state & __TASK_TRACED) != 0)
 #define task_is_stopped(task)  ((task->state & __TASK_STOPPED) != 0)