From: "Paul E. McKenney" <paulmck@kernel.org>
To: Z qiang <qiang.zhang1211@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
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 15:28:51 -0700 [thread overview]
Message-ID: <b735d174-8ad9-4ace-86ee-75dc09852537@paulmck-laptop> (raw)
In-Reply-To: <CALm+0cUesD9KaWyfsRUyGdErbrU11sAfRgRR=Qjyz7Boq9Vt=g@mail.gmail.com>
On Tue, Apr 23, 2024 at 10:20:49AM +0800, Z qiang wrote:
> >
> > 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?
This looks quite nice to me, especially given that it avoids changing
all the other calls to __do_softirq(). Some architectures might want
to directly call handle_softirqs(), but if so, they can send the patches.
Thanx, Paul
> Thanks
> Zqiang
>
> > ksoftirqd_run_end();
> > cond_resched();
> > return;
next prev parent reply other threads:[~2024-04-23 22:28 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
2024-04-23 22:28 ` Paul E. McKenney [this message]
2024-04-26 2:09 ` Z qiang
2024-04-26 17:23 ` Thomas Gleixner
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