From: "Paul E. McKenney" <paulmck@kernel.org>
To: Zqiang <qiang.zhang1211@gmail.com>
Cc: tglx@linutronix.de, frederic@kernel.org,
neeraj.upadhyay@kernel.org, joel@joelfernandes.org,
rcu@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] rcu: Fix suspicious RCU usage in __do_softirq()
Date: Mon, 29 Apr 2024 13:45:44 -0700 [thread overview]
Message-ID: <9f227fd2-13b2-4c78-b3b3-05ef6d583078@paulmck-laptop> (raw)
In-Reply-To: <20240427102808.29356-1-qiang.zhang1211@gmail.com>
On Sat, Apr 27, 2024 at 06:28:08PM +0800, Zqiang wrote:
> Currently, the condition "__this_cpu_read(ksoftirqd) == current" is
> checked to ensure the rcu_softirq_qs() is invoked in ksoftirqd tasks
> context for non-RT kernels. however, in some scenarios, this condition
> will be broken.
>
> ksoftirqd/0
> ->finish_task_switch
> ->put_task_struct_rcu_user
> ->call_rcu(&task->rcu, delayed_put_task_struct)
> ->__kasan_record_aux_stack
> ->pfn_valid
> ->rcu_read_lock_sched()
> <interrupt>
> __irq_exit_rcu
> ->__do_softirq
> -> if (!IS_ENABLED(CONFIG_PREEMPT_RT) &&
> __this_cpu_read(ksoftirqd) == current)
> ->rcu_softirq_qs
> ->RCU_LOCKDEP_WARN(lock_is_held(&rcu_sched_lock_map))
>
> The rcu quiescent states is reported occurs in the rcu-read critical
> section, so the lockdep warning is triggered. this commit therefore
> remove "__this_cpu_read(ksoftirqd) == current" condition check, generate
> new "handle_softirqs(bool kirqd)" function to replace __do_softirq() in
> run_ksoftirqdt(), and set parameter kirqd to true, make rcu_softirq_qs()
> be invoked only in ksofirqd tasks context for non-RT kernels.
>
> Reported-by: syzbot+dce04ed6d1438ad69656@syzkaller.appspotmail.com
> Link: https://lore.kernel.org/lkml/8f281a10-b85a-4586-9586-5bbc12dc784f@paulmck-laptop/T/#mea8aba4abfcb97bbf499d169ce7f30c4cff1b0e3
> Suggested-by: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: Zqiang <qiang.zhang1211@gmail.com>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
> ---
> kernel/softirq.c | 12 ++++++++----
> 1 file changed, 8 insertions(+), 4 deletions(-)
>
> 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);
> ksoftirqd_run_end();
> cond_resched();
> return;
> --
> 2.17.1
>
prev parent reply other threads:[~2024-04-29 20:45 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-27 10:28 [PATCH] rcu: Fix suspicious RCU usage in __do_softirq() Zqiang
2024-04-29 20:45 ` Paul E. McKenney [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=9f227fd2-13b2-4c78-b3b3-05ef6d583078@paulmck-laptop \
--to=paulmck@kernel.org \
--cc=frederic@kernel.org \
--cc=joel@joelfernandes.org \
--cc=linux-kernel@vger.kernel.org \
--cc=neeraj.upadhyay@kernel.org \
--cc=qiang.zhang1211@gmail.com \
--cc=rcu@vger.kernel.org \
--cc=tglx@linutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).