[PATCH 50/89] sched/core: Convert ___assert_task_state() link time assert to BUILD_BUG_ON()

Ingo Molnar
2017-02-06T13:31:08Z

The length of TASK_STATE_TO_CHAR_STR was still checked using the old
link-time manual error method - convert it to BUILD_BUG_ON(). This
has a couple of advantages:

- it's more obvious what's going on

- it reduces the size and complexity of <linux/sched.h>

- BUILD_BUG_ON() will fail during compilation, with a clearer
error message than the link time assert.

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
include/linux/sched.h | 3 ---
kernel/sched/core.c | 3 +++
2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 29262493c915..41ca94a982b6 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -74,9 +74,6 @@ struct task_group;

#define TASK_STATE_TO_CHAR_STR "RSDTtXZxKWPNn"

-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_current_state */
#define TASK_KILLABLE (TASK_WAKEKILL | TASK_UNINTERRUPTIBLE)
#define TASK_STOPPED (TASK_WAKEKILL | __TASK_STOPPED)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 568e773c528f..eee4ac12811a 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5233,6 +5233,9 @@ void sched_show_task(struct task_struct *p)
int ppid;
unsigned long state = p->state;

+ /* 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);
+
if (!try_get_task_stack(p))
return;
if (state)
--
2.7.4