schedule_debug() ignores in_atomic() if prev->exit_state != 0.
This is not what we want, ->exit_state is set by exit_notify()
but we should complain until the task does the last schedule()
in TASK_DEAD.

See also 7407251a0e2e "PF_DEAD cleanup", I think this ancient
commit explains why schedule() had to rely on ->exit_state,
until that commit exit_notify() disabled preemption and set
PF_DEAD which was used to detect the exiting task.

Signed-off-by: Oleg Nesterov <[email protected]>
---
 kernel/sched/core.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 5ac63c9..7184357 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2287,10 +2287,10 @@ static inline void schedule_debug(struct task_struct 
*prev)
 {
        /*
         * Test if we are atomic. Since do_exit() needs to call into
-        * schedule() atomically, we ignore that path for now.
-        * Otherwise, whine if we are scheduling when we should not be.
+        * schedule() atomically, we ignore that path. Otherwise whine
+        * if we are scheduling when we should not.
         */
-       if (unlikely(in_atomic_preempt_off() && !prev->exit_state))
+       if (unlikely(in_atomic_preempt_off() && prev->state != TASK_DEAD))
                __schedule_bug(prev);
        rcu_sleep_check();
 
-- 
1.5.5.1


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