sched: Fix more TASK_state comparisons

Boris reported hung_task splats after commit 5aec788aeb8e ("sched: Fix
TASK_state comparisons"). Upon closer consideration of that change it
doesn't only exclude TASK_KILLABLE, but also TASK_IDLE.

Update the comment to reflect this fact and add an additional
TASK_NOLOAD test to exclude them.

Additionally, remove the TASK_FREEZABLE early exit from
check_hung_task(), a freezable task is not a frozen task.

Fixes: 5aec788aeb8e ("sched: Fix TASK_state comparisons")
Reported-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Borislav Petkov <bp@alien8.de>

diff --git a/kernel/hung_task.c b/kernel/hung_task.c
index 3a15169..c71889f 100644 (file)
--- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -95,7 +95,7 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
         * Ensure the task is not frozen.
         * Also, skip vfork and any other user process that freezer should skip.
         */
-       if (unlikely(READ_ONCE(t->__state) & (TASK_FREEZABLE | TASK_FROZEN)))
+       if (unlikely(READ_ONCE(t->__state) & TASK_FROZEN))
                return;
 
        /*
@@ -200,10 +200,14 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
                                goto unlock;
                        last_break = jiffies;
                }
-               /* skip the TASK_KILLABLE tasks -- these can be killed */
+               /*
+                * skip the TASK_KILLABLE tasks -- these can be killed
+                * skip the TASK_IDLE tasks -- those are genuinely idle
+                */
                state = READ_ONCE(t->__state);
                if ((state & TASK_UNINTERRUPTIBLE) &&
-                   !(state & TASK_WAKEKILL))
+                   !(state & TASK_WAKEKILL) &&
+                   !(state & TASK_NOLOAD))
                        check_hung_task(t, timeout);
        }
  unlock: