linux-kernel - Re: [RFC][PATCH v2 19/31] timers: net: Use del_timer

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Date:   Thu, 27 Oct 2022 16:13:55 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Stephen Boyd <sboyd@...nel.org>,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
        Tony Nguyen <anthony.l.nguyen@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Mirko Lindner <mlindner@...vell.com>,
        Stephen Hemminger <stephen@...workplumber.org>,
        Martin KaFai Lau <martin.lau@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Kuniyuki Iwashima <kuniyu@...zon.com>,
        Pavel Begunkov <asml.silence@...il.com>,
        Menglong Dong <imagedong@...cent.com>,
        linux-usb@...r.kernel.org, linux-wireless@...r.kernel.org,
        bridge@...ts.linux-foundation.org, netfilter-devel@...r.kernel.org,
        coreteam@...filter.org, lvs-devel@...r.kernel.org,
        linux-afs@...ts.infradead.org, linux-nfs@...r.kernel.org,
        tipc-discussion@...ts.sourceforge.net
Subject: Re: [RFC][PATCH v2 19/31] timers: net: Use del_timer_shutdown()
 before freeing timer

On Thu, Oct 27, 2022 at 05:07:55PM -0400, Steven Rostedt wrote:
> On Thu, 27 Oct 2022 16:34:53 -0400
> Steven Rostedt <rostedt@...dmis.org> wrote:
> 
> > What about del_timer_try_shutdown(), that if it removes the timer, it sets
> > the function to NULL (making it equivalent to a successful shutdown),
> > otherwise it does nothing. Allowing the the timer to be rearmed.
> > 
> > I think this would work in this case.
> 
> Guenter,
> 
> Can you apply this patch on top of the series, and see if it makes the
> warning go away?

Applied, and started testing.

Please let me know if I am missing some other patch(es) to apply.

Thanks,
Guenter

> 
> diff --git a/include/linux/timer.h b/include/linux/timer.h
> index d4d90149d015..e3c5f4bdd526 100644
> --- a/include/linux/timer.h
> +++ b/include/linux/timer.h
> @@ -184,12 +184,23 @@ static inline int timer_pending(const struct timer_list * timer)
>  	return !hlist_unhashed_lockless(&timer->entry);
>  }
>  
> +extern int __del_timer(struct timer_list * timer, bool free);
> +
>  extern void add_timer_on(struct timer_list *timer, int cpu);
> -extern int del_timer(struct timer_list * timer);
>  extern int mod_timer(struct timer_list *timer, unsigned long expires);
>  extern int mod_timer_pending(struct timer_list *timer, unsigned long expires);
>  extern int timer_reduce(struct timer_list *timer, unsigned long expires);
>  
> +static inline int del_timer_try_shutdown(struct timer_list *timer)
> +{
> +	return __del_timer(timer, true);
> +}
> +
> +static inline int del_timer(struct timer_list *timer)
> +{
> +	return __del_timer(timer, false);
> +}
> +
>  /*
>   * The jiffies value which is added to now, when there is no timer
>   * in the timer wheel:
> diff --git a/kernel/time/timer.c b/kernel/time/timer.c
> index 7305c65ad0eb..073031cb3bb9 100644
> --- a/kernel/time/timer.c
> +++ b/kernel/time/timer.c
> @@ -1255,7 +1255,7 @@ EXPORT_SYMBOL_GPL(add_timer_on);
>   * (ie. del_timer() of an inactive timer returns 0, del_timer() of an
>   * active timer returns 1.)
>   */
> -int del_timer(struct timer_list *timer)
> +int __del_timer(struct timer_list *timer, bool free)
>  {
>  	struct timer_base *base;
>  	unsigned long flags;
> @@ -1266,12 +1266,16 @@ int del_timer(struct timer_list *timer)
>  	if (timer_pending(timer)) {
>  		base = lock_timer_base(timer, &flags);
>  		ret = detach_if_pending(timer, base, true);
> +		if (free && ret) {
> +			timer->function = NULL;
> +			debug_timer_deactivate(timer);
> +		}
>  		raw_spin_unlock_irqrestore(&base->lock, flags);
>  	}
>  
>  	return ret;
>  }
> -EXPORT_SYMBOL(del_timer);
> +EXPORT_SYMBOL(__del_timer);
>  
>  static int __try_to_del_timer_sync(struct timer_list *timer, bool free)
>  {
> diff --git a/net/core/sock.c b/net/core/sock.c
> index 10cc84379d75..23a97442a0a6 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -3345,7 +3345,7 @@ EXPORT_SYMBOL(sk_reset_timer);
>  
>  void sk_stop_timer(struct sock *sk, struct timer_list* timer)
>  {
> -	if (del_timer(timer))
> +	if (del_timer_try_shutdown(timer))
>  		__sock_put(sk);
>  }
>  EXPORT_SYMBOL(sk_stop_timer);