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Subject[tip:sched/urgent] sched: Assert task state bits at build time
Commit-ID:  e1781538cf5c870ab696e9b8f0a5c498d3900f2f
Gitweb: http://git.kernel.org/tip/e1781538cf5c870ab696e9b8f0a5c498d3900f2f
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Thu, 17 Dec 2009 13:16:30 +0100
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Thu, 17 Dec 2009 13:22:45 +0100

sched: Assert task state bits at build time

Since everybody is lazy and prone to forgetting things, make the
compiler help us a bit.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20091217121830.060186433@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
fs/proc/array.c | 18 ++++++++++--------
include/linux/sched.h | 4 ++++
2 files changed, 14 insertions(+), 8 deletions(-)
diff --git a/fs/proc/array.c b/fs/proc/array.c
index 96361e8..f560325 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -134,14 +134,14 @@ static inline void task_name(struct seq_file *m, struct task_struct *p)
* simple bit tests.
*/
static const char *task_state_array[] = {
- "R (running)", /* 0 */
- "S (sleeping)", /* 1 */
- "D (disk sleep)", /* 2 */
- "T (stopped)", /* 4 */
- "t (tracing stop)", /* 8 */
- "Z (zombie)", /* 16 */
- "X (dead)", /* 32 */
- "x (dead)", /* 64 */
+ "R (running)", /* 0 */
+ "S (sleeping)", /* 1 */
+ "D (disk sleep)", /* 2 */
+ "T (stopped)", /* 4 */
+ "t (tracing stop)", /* 8 */
+ "Z (zombie)", /* 16 */
+ "X (dead)", /* 32 */
+ "x (dead)", /* 64 */
"K (wakekill)", /* 128 */
"W (waking)", /* 256 */
};
@@ -151,6 +151,8 @@ static inline const char *get_task_state(struct task_struct *tsk)
unsigned int state = (tsk->state & TASK_REPORT) | tsk->exit_state;
const char **p = &task_state_array[0];

+ BUILD_BUG_ON(1 + ilog2(TASK_STATE_MAX) != ARRAY_SIZE(task_state_array));
+
while (state) {
p++;
state >>= 1;
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 94858df..3754387 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -192,9 +192,13 @@ print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq)
#define TASK_DEAD 64
#define TASK_WAKEKILL 128
#define TASK_WAKING 256
+#define TASK_STATE_MAX 512

#define TASK_STATE_TO_CHAR_STR "RSDTtZXxKW"

+extern char ___assert_task_state[1 - 2*!!(
+ sizeof(TASK_STATE_TO_CHAR_STR)-1 != ilog2(TASK_STATE_MAX)+1)];
+
/* Convenience macros for the sake of set_task_state */
#define TASK_KILLABLE (TASK_WAKEKILL | TASK_UNINTERRUPTIBLE)
#define TASK_STOPPED (TASK_WAKEKILL | __TASK_STOPPED)

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