linux-kernel - Re: [RFC][PATCH v2 20/31] timers: usb: Use del_timer

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Date:   Sun, 30 Oct 2022 11:48:28 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Stephen Boyd <sboyd@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Felipe Balbi <balbi@...nel.org>,
        Johan Hovold <johan@...nel.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Mathias Nyman <mathias.nyman@...ux.intel.com>,
        Kai-Heng Feng <kai.heng.feng@...onical.com>,
        Matthias Kaehlcke <mka@...omium.org>,
        Michael Grzeschik <m.grzeschik@...gutronix.de>,
        Bhuvanesh Surachari <Bhuvanesh_Surachari@...tor.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        linux-usb@...r.kernel.org, Tejun Heo <tj@...nel.org>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        John Stultz <jstultz@...gle.com>
Subject: Re: [RFC][PATCH v2 20/31] timers: usb: Use del_timer_shutdown()
 before freeing timer

On Sat, 29 Oct 2022 15:56:25 -0700
Guenter Roeck <linux@...ck-us.net> wrote:

> >> WARNING: CPU: 0 PID: 9 at lib/debugobjects.c:502 debug_print_object+0xd0/0x100
> >> ODEBUG: free active (active state 0) object type: timer_list hint: neigh_timer_handler+0x0/0x480
> >>
> >> That happens with almost every test, so I may have missed some others
> >> in the noise.  
> > 
> > Can you add this?
> >   
> 
> It doesn't make a difference.

Ah, it also requires this (I have other debugging in that file, so it may
only apply with some fuzzing):

-- Steve


diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index ac2e8beb4235..f2ccf24a8448 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -1282,6 +1296,11 @@ int __del_timer(struct timer_list *timer, bool free)
 			debug_timer_deactivate(timer, true);
 		}
 		raw_spin_unlock_irqrestore(&base->lock, flags);
+	} else if (free) {
+		base = lock_timer_base(timer, &flags);
+		timer->function = NULL;
+		debug_timer_deactivate(timer, true);
+		raw_spin_unlock_irqrestore(&base->lock, flags);
 	}
 
 	return ret;