On Mon, Jun 07, 2021 at 11:45:00AM +0100, Daniel Thompson wrote:

On Wed, Jun 02, 2021 at 03:12:31PM +0200, Peter Zijlstra wrote:

quoted

Change the type and name of task_struct::state. Drop the volatile and
shrink it to an 'unsigned int'. Rename it in order to find all uses
such that we can use READ_ONCE/WRITE_ONCE as appropriate.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 ...
 kernel/debug/kdb/kdb_support.c |   18 +++++++------
 ...

--- a/kernel/debug/kdb/kdb_support.c
+++ b/kernel/debug/kdb/kdb_support.c

@@ -609,23 +609,25 @@ unsigned long kdb_task_state_string(cons
  */
 char kdb_task_state_char (const struct task_struct *p)
 {
-	int cpu;
-	char state;
+	unsigned int p_state;
 	unsigned long tmp;
+	char state;
+	int cpu;
 
 	if (!p ||
 	    copy_from_kernel_nofault(&tmp, (char *)p, sizeof(unsigned long)))
 		return 'E';
 
 	cpu = kdb_process_cpu(p);
-	state = (p->state == 0) ? 'R' :
-		(p->state < 0) ? 'U' :
-		(p->state & TASK_UNINTERRUPTIBLE) ? 'D' :
-		(p->state & TASK_STOPPED) ? 'T' :
-		(p->state & TASK_TRACED) ? 'C' :
+	p_state = READ_ONCE(p->__state);
+	state = (p_state == 0) ? 'R' :
+		(p_state < 0) ? 'U' :

Looks like the U here stands for Unreachable since this patch makes it
more obvious that this clause is (and previously was) exactly that!

Dropping the U state would be good since I guess this will show up as a
"new" warning in some tools. However it was a preexisting problem so with
or without this cleaned up:
Acked-by: Daniel Thompson <redacted>

Thanks!

Note that there's a second instance of this exact code in
arch/powerpc/xmon/xmon.c, with the same 'U' issue.

I'll repost this soon, as it seems I've fixed all robot failout (fingers
crossed).