Re: [PATCH] powerpc/xmon: fix task state output

On 10/27/21, Michael Ellerman [off-list ref] wrote:

Denis Kirjanov [off-list ref] writes:

quoted

p_state is unsigned since the commit 2f064a59a11f

The patch also uses TASK_RUNNING instead of null.

Fixes: 2f064a59a11f ("sched: Change task_struct::state")
Signed-off-by: Denis Kirjanov <redacted>
---
 arch/powerpc/xmon/xmon.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index dd8241c009e5..8b28ff9d98d1 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c

@@ -3264,8 +3264,7 @@ static void show_task(struct task_struct *volatile

tsk)
 	 * appropriate for calling from xmon. This could be moved
 	 * to a common, generic, routine used by both.
 	 */
-	state = (p_state == 0) ? 'R' :
-		(p_state < 0) ? 'U' :

I guess 'U' meant 'unknown'? I always thought it meant uninterruptible,
but obviously that is 'D'.

Right.

quoted

+	state = (p_state == TASK_RUNNING) ? 'R' :
 		(p_state & TASK_UNINTERRUPTIBLE) ? 'D' :
 		(p_state & TASK_STOPPED) ? 'T' :
 		(p_state & TASK_TRACED) ? 'C' :

I think a better cleanup would be to use task_is_running(),
task_is_traced(), task_is_stopped(). That way we're insulated somewhat
from any future changes.

In this case we end up with some states wrapped with a macro but
others are still explicitly checked using p_state variable.

That would add additional READ_ONCE()s of the state, but I don't think
we care, the task should not be running if the system is in xmon.

cheers