Hi Paul, On Mon, 8 July 2024, Paul E. McKenney wrote: >On Fri, Jun 28, 2024 at 01:18:26PM +0900, [email protected] wrote: >> From: Ryo Takakura <[email protected]> >> >> 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 <[email protected]> > >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. Sincerely, Ryo Takakura > >------------------------------------------------------------------------ > >commit ad6647a70f239aa9f2741b2f5a828a4483122a26 >Author: Ryo Takakura <[email protected]> >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 <[email protected]> > Signed-off-by: Paul E. McKenney <[email protected]> > >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();
