[PATCH v2 0/4] Fix put_task_struct() calls under PREEMPT_RT

Wander Lairson Costa
2023-01-20T15:03:54Z

put_task_struct() decrements a usage counter and calls
__put_task_struct() if the counter reaches zero.

__put_task_struct() indirectly acquires a spinlock, which is a sleeping
lock under PREEMPT_RT. Therefore, we can't call put_task_struct() in an
atomic context in RT kernels.

This patch series introduces put_task_struct_atomic_safe(), which defers
the call to __put_task_struct() to a process context when compiled with
PREEMPT_RT.

It also fixes known problematic call sites.

Changelog:
==========

v2:
* Add the put_task_struct_atomic_safe() function that is responsible for
handling the conditions to call put_task_struct().
* Replace put_task_struct() by put_task_struct_atomic_safe() in known
atomic call sites.

Wander Lairson Costa (4):
sched/task: Add the put_task_struct_atomic_safe function
sched/deadline: fix inactive_task_timer splat
sched/rt: use put_task_struct_atomic_safe() to avoid potential splat
sched/core: use put_task_struct_atomic_safe() to avoid potential splat

include/linux/sched/task.h | 21 +++++++++++++++++++++
kernel/fork.c | 8 ++++++++
kernel/sched/core.c | 2 +-
kernel/sched/deadline.c | 2 +-
kernel/sched/rt.c | 4 ++--
5 files changed, 33 insertions(+), 4 deletions(-)

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2.39.0