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From: Z qiang <qiang.zhang1211@gmail.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: paulmck@kernel.org,
	 syzbot <syzbot+dce04ed6d1438ad69656@syzkaller.appspotmail.com>,
	 linux-kernel@vger.kernel.org, peterz@infradead.org,
	 syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot] [kernel?] WARNING: suspicious RCU usage in __do_softirq
Date: Tue, 23 Apr 2024 10:20:49 +0800	[thread overview]
Message-ID: <CALm+0cUesD9KaWyfsRUyGdErbrU11sAfRgRR=Qjyz7Boq9Vt=g@mail.gmail.com> (raw)
In-Reply-To: <87o7a1umj3.ffs@tglx>

>
> On Fri, Apr 19 2024 at 13:50, Z qiang wrote:
> >> On Thu, Apr 18, 2024 at 05:49:38PM +0800, Z qiang wrote:
> >  static __init int spawn_ksoftirqd(void)
> >  {
> > +       int cpu;
> > +
> > +       for_each_possible_cpu(cpu)
> > +               per_cpu(ksoftirqd_work, cpu) = false;
>
> First of all that initialization is pointless, but why making all of
> this complex as hell?
>
> Thanks,
>
>         tglx
> ---
> diff --git a/kernel/softirq.c b/kernel/softirq.c
> index b315b21fb28c..e991d735be0d 100644
> --- a/kernel/softirq.c
> +++ b/kernel/softirq.c
> @@ -508,7 +508,7 @@ static inline bool lockdep_softirq_start(void) { return false; }
>  static inline void lockdep_softirq_end(bool in_hardirq) { }
>  #endif
>
> -asmlinkage __visible void __softirq_entry __do_softirq(void)
> +static void handle_softirqs(bool kirqd)
>  {
>         unsigned long end = jiffies + MAX_SOFTIRQ_TIME;
>         unsigned long old_flags = current->flags;
> @@ -563,8 +563,7 @@ asmlinkage __visible void __softirq_entry __do_softirq(void)
>                 pending >>= softirq_bit;
>         }
>
> -       if (!IS_ENABLED(CONFIG_PREEMPT_RT) &&
> -           __this_cpu_read(ksoftirqd) == current)
> +       if (!IS_ENABLED(CONFIG_PREEMPT_RT) && kirqd)
>                 rcu_softirq_qs();
>
>         local_irq_disable();
> @@ -584,6 +583,11 @@ asmlinkage __visible void __softirq_entry __do_softirq(void)
>         current_restore_flags(old_flags, PF_MEMALLOC);
>  }
>
> +asmlinkage __visible void __softirq_entry __do_softirq(void)
> +{
> +       handle_softirqs(false);
> +}
> +
>  /**
>   * irq_enter_rcu - Enter an interrupt context with RCU watching
>   */
> @@ -921,7 +925,7 @@ static void run_ksoftirqd(unsigned int cpu)
>                  * We can safely run softirq on inline stack, as we are not deep
>                  * in the task stack here.
>                  */
> -               __do_softirq();
> +               handle_softirqs(true);

Thanks, this is good for me :),
Paul, what do you think?

Thanks
Zqiang

>                 ksoftirqd_run_end();
>                 cond_resched();
>                 return;

next prev parent reply	other threads:[~2024-04-23  2:21 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-04-02 18:05 [syzbot] [kernel?] WARNING: suspicious RCU usage in __do_softirq syzbot
2024-04-16  7:05 ` syzbot
2024-04-16  8:10 ` Z qiang
2024-04-16  8:44   ` Z qiang
2024-04-17  1:13     ` Paul E. McKenney
2024-04-17  2:25       ` Z qiang
2024-04-17 22:39         ` Paul E. McKenney
2024-04-18  9:49           ` Z qiang
2024-04-18 22:49             ` Paul E. McKenney
2024-04-19  5:50               ` Z qiang
2024-04-19  6:11                 ` Z qiang
2024-04-19  7:12                 ` Paul E. McKenney
2024-04-19  7:29                   ` Z qiang
2024-04-22 21:15                 ` Thomas Gleixner
2024-04-23  2:20                   ` Z qiang [this message]
2024-04-23 22:28                     ` Paul E. McKenney
2024-04-26  2:09                       ` Z qiang
2024-04-26 17:23                         ` Thomas Gleixner

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