On Fri, Sep 15, 2023 at 01:44:44PM -0400, Liam R. Howlett wrote: > Initial booting is setting the task flag to idle (PF_IDLE) by the call > path sched_init() -> init_idle(). Having the task idle and calling > call_rcu() in kernel/rcu/tiny.c means that TIF_NEED_RESCHED will be > set. Subsequent calls to any cond_resched() will enable IRQs, > potentially earlier than the IRQ setup has completed. Recent changes > have caused just this scenario and IRQs have been enabled early. > > This causes a warning later in start_kernel() as interrupts are enabled > before they are fully set up. > > Fix this issue by setting the PF_IDLE flag later in the boot sequence. > > Although the boot task was marked as idle since (at least) d80e4fda576d, > I am not sure that it is wrong to do so. The forced context-switch on > idle task was introduced in the tiny_rcu update, so I'm going to claim > this fixes 5f6130fa52ee. > > Link: https://lore.kernel.org/linux-mm/87v8cv22jh.fsf@mail.lhotse/ > Link: https://lore.kernel.org/linux-mm/CAMuHMdWpvpWoDa=Ox-do92czYRvkok6_x6pYUH+ZouMcJbXy+Q@xxxxxxxxxxxxxx/ > Fixes: 5f6130fa52ee ("tiny_rcu: Directly force QS when call_rcu_[bh|sched]() on idle_task") > Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx> > --- Thanks!, I've queued this up for sched/urgent but will let the robots at it before I push it out to -tip.
