On Tue, Jul 09, 2024 at 02:34:26PM +0900, takakura@xxxxxxxxxxxxx wrote:
> Hi Paul,
>
> On Mon, 8 July 2024, Paul E. McKenney wrote:
> >On Fri, Jun 28, 2024 at 01:18:26PM +0900, takakura@xxxxxxxxxxxxx wrote:
> >> From: Ryo Takakura <takakura@xxxxxxxxxxxxx>
> >>
> >> The commit 2d7f00b2f0130 ("rcu: Suppress smp_processor_id() complaint
> >> in synchronize_rcu_expedited_wait()") disabled preemption around
> >> dump_cpu_task() to suppress warning on its usage within preemtible context.
> >>
> >> Calling dump_cpu_task() doesn't required to be in non-preemptible context
> >> except for suppressing the smp_processor_id() warning.
> >> As the smp_processor_id() is evaluated along with in_hardirq()
> >> to check if it's in interrupt context, this patch removes the need
> >> for its preemtion disablement by reordering the condition so that
> >> smp_processor_id() only gets evaluated when it's in interrupt context.
> >>
> >> Signed-off-by: Ryo Takakura <takakura@xxxxxxxxxxxxx>
> >
> >Hearing no objections, I pulled this in for further review and testing.
> >
> >I had to hand-apply this due to a recent conflicting change in the
> >-rcu tree, so could you please check the version below in case I messed
> >something up?
> >
> > Thanx, Paul
>
> Thanks for preparing the patch!
> I checked it on the rcu tree and looks good to me.
>
> If possible, could you replace the title with s/rcu_dump_task()/dump_cpu_task()/
> when applying?
> I made a mistake with the title where dump_cpu_task() is the one being modified,
> not rcu_dump_task(). I'm sorry for the confusion.
Thank you for calling my attention to this.
Done locally, and it will show up on my next rebase.
Thanx, Paul
> Sincerely,
> Ryo Takakura
>
> >
> >------------------------------------------------------------------------
> >
> >commit ad6647a70f239aa9f2741b2f5a828a4483122a26
> >Author: Ryo Takakura <takakura@xxxxxxxxxxxxx>
> >Date: Fri Jun 28 13:18:26 2024 +0900
> >
> > rcu: Let rcu_dump_task() be used without preemption disabled
> >
> > The commit 2d7f00b2f0130 ("rcu: Suppress smp_processor_id() complaint
> > in synchronize_rcu_expedited_wait()") disabled preemption around
> > dump_cpu_task() to suppress warning on its usage within preemtible context.
> >
> > Calling dump_cpu_task() doesn't required to be in non-preemptible context
> > except for suppressing the smp_processor_id() warning.
> > As the smp_processor_id() is evaluated along with in_hardirq()
> > to check if it's in interrupt context, this patch removes the need
> > for its preemtion disablement by reordering the condition so that
> > smp_processor_id() only gets evaluated when it's in interrupt context.
> >
> > Signed-off-by: Ryo Takakura <takakura@xxxxxxxxxxxxx>
> > Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
> >
> >diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h
> >index d4be644afb50..c5d9a7eb0803 100644
> >--- a/kernel/rcu/tree_exp.h
> >+++ b/kernel/rcu/tree_exp.h
> >@@ -597,9 +597,7 @@ static void synchronize_rcu_expedited_stall(unsigned long jiffies_start, unsigne
> > mask = leaf_node_cpu_bit(rnp, cpu);
> > if (!(READ_ONCE(rnp->expmask) & mask))
> > continue;
> >- preempt_disable(); // For smp_processor_id() in dump_cpu_task().
> > dump_cpu_task(cpu);
> >- preempt_enable();
> > }
> > rcu_exp_print_detail_task_stall_rnp(rnp);
> > }
> >diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> >index 05afa2932b5e..bdb0e0328f6a 100644
> >--- a/kernel/sched/core.c
> >+++ b/kernel/sched/core.c
> >@@ -11485,7 +11485,7 @@ struct cgroup_subsys cpu_cgrp_subsys = {
> >
> > void dump_cpu_task(int cpu)
> > {
> >- if (cpu == smp_processor_id() && in_hardirq()) {
> >+ if (in_hardirq() && cpu == smp_processor_id()) {
> > struct pt_regs *regs;
> >
> > regs = get_irq_regs();
