Re: [RFC][PATCH v2 19/31] timers: net: Use del_timer_shutdown() before freeing timer

[Steven Rostedt <rostedt@xxxxxxxxxxx>]

On Thu, 27 Oct 2022 16:34:53 -0400
Steven Rostedt <rostedt@xxxxxxxxxxx> 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?

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);