From: Tejun Heo <tj@kernel.org> mainline inclusion from mainline-v6.12-rc1 commit 9753358a6a2b011478e8efdabbb489216252426f category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/IDC9YK Reference: https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commi... -------------------------------- scx_ops_enable() has two task iteration loops. The first one calls scx_ops_init_task() on every task and the latter switches the eligible ones into SCX. The first loop left the tasks in SCX_TASK_INIT state and then the second loop switched it into READY before switching the task into SCX. The distinction between INIT and READY is only meaningful in the fork path where it's used to tell whether the task finished forking so that we can tell ops.exit_task() accordingly. Leaving task in INIT state between the two loops is incosistent with the fork path and incorrect. The following can be triggered by running a program which keeps toggling a task between SCHED_OTHER and SCHED_SCX while enabling a task: sched_ext: Invalid task state transition 1 -> 3 for fish[1526] WARNING: CPU: 2 PID: 1615 at kernel/sched/ext.c:3393 scx_ops_enable_task+0x1a1/0x200 ... Sched_ext: qmap (enabling+all) RIP: 0010:scx_ops_enable_task+0x1a1/0x200 ... switching_to_scx+0x13/0xa0 __sched_setscheduler+0x850/0xa50 do_sched_setscheduler+0x104/0x1c0 __x64_sys_sched_setscheduler+0x18/0x30 do_syscall_64+0x7b/0x140 entry_SYSCALL_64_after_hwframe+0x76/0x7e Fix it by transitioning to READY in the first loop right after scx_ops_init_task() succeeds. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: David Vernet <void@manifault.com> Signed-off-by: Zicheng Qu <quzicheng@huawei.com> --- kernel/sched/ext.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index c03d398f4248..7a1b7c43708b 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -5174,6 +5174,8 @@ static int scx_ops_enable(struct sched_ext_ops *ops) goto err_disable_unlock_all; } + scx_set_task_state(p, SCX_TASK_READY); + put_task_struct(p); spin_lock_irq(&scx_tasks_lock); } @@ -5186,7 +5188,7 @@ static int scx_ops_enable(struct sched_ext_ops *ops) WRITE_ONCE(scx_switching_all, !(ops->flags & SCX_OPS_SWITCH_PARTIAL)); /* - * We're fully committed and can't fail. The PREPPED -> ENABLED + * We're fully committed and can't fail. The task READY -> ENABLED * transitions here are synchronized against sched_ext_free() through * scx_tasks_lock. */ @@ -5198,7 +5200,6 @@ static int scx_ops_enable(struct sched_ext_ops *ops) sched_deq_and_put_task(p, DEQUEUE_SAVE | DEQUEUE_MOVE, &ctx); - scx_set_task_state(p, SCX_TASK_READY); __setscheduler_prio(p, p->prio); check_class_changing(task_rq(p), p, old_class); -- 2.34.1