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Date: Wed, 26 Mar 2014 19:53:27 +0100 (CET)
From: Julia Lawall <julia.lawall@...6.fr>
To: Thomas Gleixner <tglx@...utronix.de>
cc: LKML <linux-kernel@...r.kernel.org>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [patch 00/16] timers: Plug debugobject leaks and use del_timer_sync()
in exit/teardown
I was looking at some cases that are marked as possibly insufficient. Is
the issue that mod_timer or add_timer is called in some function that is
not the timer interrupt handler (or the function that starts the timer
running in the first place)?
julia
On Tue, 25 Mar 2014, Thomas Gleixner wrote:
> On Sun, 23 Mar 2014, Julia Lawall wrote:
> > diff -u -p a/arch/mips/lasat/picvue_proc.c b/arch/mips/lasat/picvue_proc.c
> > --- a/arch/mips/lasat/picvue_proc.c
> > +++ b/arch/mips/lasat/picvue_proc.c
> > @@ -175,7 +175,7 @@ static void pvc_proc_cleanup(void)
> > remove_proc_entry("scroll", pvc_display_dir);
> > remove_proc_entry(DISPLAY_DIR_NAME, NULL);
> >
> > - del_timer(&timer);
> > + del_timer_sync(&timer);
>
> Correct.
>
> > }
> >
> > static int __init pvc_proc_init(void)
> > diff -u -p a/drivers/tty/serial/mux.c b/drivers/tty/serial/mux.c
> > --- a/drivers/tty/serial/mux.c
> > +++ b/drivers/tty/serial/mux.c
> > @@ -613,7 +613,7 @@ static void __exit mux_exit(void)
> > {
> > /* Delete the Mux timer. */
> > if(port_cnt > 0) {
> > - del_timer(&mux_timer);
> > + del_timer_sync(&mux_timer);
>
> Correct.
>
> > #ifdef CONFIG_SERIAL_MUX_CONSOLE
> > unregister_console(&mux_console);
> > #endif
> > diff -u -p a/drivers/input/serio/hp_sdc.c b/drivers/input/serio/hp_sdc.c
> > --- a/drivers/input/serio/hp_sdc.c
> > +++ b/drivers/input/serio/hp_sdc.c
> > @@ -984,7 +984,7 @@ static void hp_sdc_exit(void)
> > free_irq(hp_sdc.irq, &hp_sdc);
> > write_unlock_irq(&hp_sdc.lock);
> >
> > - del_timer(&hp_sdc.kicker);
> > + del_timer_sync(&hp_sdc.kicker);
>
> Correct.
>
> > tasklet_kill(&hp_sdc.task);
> >
> > diff -u -p a/drivers/isdn/sc/init.c b/drivers/isdn/sc/init.c
> > --- a/drivers/isdn/sc/init.c
> > +++ b/drivers/isdn/sc/init.c
> > @@ -390,8 +390,8 @@ static void __exit sc_exit(void)
> > /*
> > * kill the timers
> > */
> > - del_timer(&(sc_adapter[i]->reset_timer));
> > - del_timer(&(sc_adapter[i]->stat_timer));
> > + del_timer_sync(&(sc_adapter[i]->reset_timer));
> > + del_timer_sync(&(sc_adapter[i]->stat_timer));
>
> Correct.
>
> > /*
> > * Tell I4L we're toast
> > diff -u -p a/drivers/isdn/i4l/isdn_common.c b/drivers/isdn/i4l/isdn_common.c
> > --- a/drivers/isdn/i4l/isdn_common.c
> > +++ b/drivers/isdn/i4l/isdn_common.c
> > @@ -2381,7 +2381,7 @@ static void __exit isdn_exit(void)
> > }
> > isdn_tty_exit();
> > unregister_chrdev(ISDN_MAJOR, "isdn");
> > - del_timer(&dev->timer);
> > + del_timer_sync(&dev->timer);
>
> Correct.
>
> > /* call vfree with interrupts enabled, else it will hang */
> > vfree(dev);
> > printk(KERN_NOTICE "ISDN-subsystem unloaded\n");
> > diff -u -p a/drivers/isdn/hardware/mISDN/hfcpci.c b/drivers/isdn/hardware/mISDN/hfcpci.c
> > --- a/drivers/isdn/hardware/mISDN/hfcpci.c
> > +++ b/drivers/isdn/hardware/mISDN/hfcpci.c
> > @@ -2352,7 +2352,7 @@ static void __exit
> > HFC_cleanup(void)
> > {
> > if (timer_pending(&hfc_tl))
> > - del_timer(&hfc_tl);
> > + del_timer_sync(&hfc_tl);
>
> That's incomplete the timer_pending() check is racy as well and the
> timer is rearming itself from the callback.
>
> > pci_unregister_driver(&hfc_driver);
> > }
> > diff -u -p a/drivers/isdn/act2000/module.c b/drivers/isdn/act2000/module.c
> > --- a/drivers/isdn/act2000/module.c
> > +++ b/drivers/isdn/act2000/module.c
> > @@ -796,7 +796,7 @@ static void __exit act2000_exit(void)
> > act2000_card *last;
> > while (card) {
> > unregister_card(card);
> > - del_timer(&card->ptimer);
> > + del_timer_sync(&card->ptimer);
>
> Correct.
>
> > card = card->next;
> > }
> > card = cards;
> > diff -u -p a/drivers/net/hamradio/yam.c b/drivers/net/hamradio/yam.c
> > --- a/drivers/net/hamradio/yam.c
> > +++ b/drivers/net/hamradio/yam.c
> > @@ -1184,7 +1184,7 @@ static void __exit yam_cleanup_driver(vo
> > struct yam_mcs *p;
> > int i;
> >
> > - del_timer(&yam_timer);
> > + del_timer_sync(&yam_timer);
>
> Correct.
>
> > for (i = 0; i < NR_PORTS; i++) {
> > struct net_device *dev = yam_devs[i];
> > if (dev) {
> > diff -u -p a/drivers/staging/speakup/main.c b/drivers/staging/speakup/main.c
> > --- a/drivers/staging/speakup/main.c
> > +++ b/drivers/staging/speakup/main.c
> > @@ -2218,7 +2218,7 @@ static void __exit speakup_exit(void)
> > unregister_keyboard_notifier(&keyboard_notifier_block);
> > unregister_vt_notifier(&vt_notifier_block);
> > speakup_unregister_devsynth();
> > - del_timer(&cursor_timer);
> > + del_timer_sync(&cursor_timer);
>
> Not sure about that one as the timer might be rearmed, so the
> invocation might need to be further down the cleanup path.
>
> > kthread_stop(speakup_task);
> > speakup_task = NULL;
> > mutex_lock(&spk_mutex);
> > diff -u -p a/drivers/staging/panel/panel.c b/drivers/staging/panel/panel.c
> > --- a/drivers/staging/panel/panel.c
> > +++ b/drivers/staging/panel/panel.c
> > @@ -2298,7 +2298,7 @@ static void __exit panel_cleanup_module(
> > unregister_reboot_notifier(&panel_notifier);
> >
> > if (scan_timer.function != NULL)
> > - del_timer(&scan_timer);
> > + del_timer_sync(&scan_timer);
>
> Correct.
>
> > if (pprt != NULL) {
> > if (keypad_enabled) {
> > diff -u -p a/drivers/staging/lustre/lustre/llite/super25.c b/drivers/staging/lustre/lustre/llite/super25.c
> > --- a/drivers/staging/lustre/lustre/llite/super25.c
> > +++ b/drivers/staging/lustre/lustre/llite/super25.c
> > @@ -197,7 +197,7 @@ static void __exit exit_lustre_lite(void
> > {
> > ll_xattr_fini();
> > vvp_global_fini();
> > - del_timer(&ll_capa_timer);
> > + del_timer_sync(&ll_capa_timer);
>
> Looks wrong, as the timer might be rearmed by the thread which is
> not yet stopped.
>
> > ll_capa_thread_stop();
> > LASSERTF(capa_count[CAPA_SITE_CLIENT] == 0,
> > "client remaining capa count %d\n",
> > diff -u -p a/drivers/atm/idt77105.c b/drivers/atm/idt77105.c
> > --- a/drivers/atm/idt77105.c
> > +++ b/drivers/atm/idt77105.c
> > @@ -369,8 +369,8 @@ EXPORT_SYMBOL(idt77105_init);
> > static void __exit idt77105_exit(void)
> > {
> > /* turn off timers */
> > - del_timer(&stats_timer);
> > - del_timer(&restart_timer);
> > + del_timer_sync(&stats_timer);
> > + del_timer_sync(&restart_timer);
>
> Yep.
>
> > }
> >
> > module_exit(idt77105_exit);
> > diff -u -p a/drivers/atm/nicstar.c b/drivers/atm/nicstar.c
> > --- a/drivers/atm/nicstar.c
> > +++ b/drivers/atm/nicstar.c
> > @@ -306,7 +306,7 @@ static void __exit nicstar_cleanup(void)
> > {
> > XPRINTK("nicstar: nicstar_cleanup() called.\n");
> >
> > - del_timer(&ns_timer);
> > + del_timer_sync(&ns_timer);
> >
>
> The driver might still be in use, as the devices are shut down via the
> pci_unregister_driver() call below. So while it's correct to use
> del_timer_sync() it's not clear w/o digging deeper into the code
> whether it's actually sufficient.
>
> > pci_unregister_driver(&nicstar_driver);
> >
> > diff -u -p a/drivers/atm/iphase.c b/drivers/atm/iphase.c
> > --- a/drivers/atm/iphase.c
> > +++ b/drivers/atm/iphase.c
> > @@ -3289,7 +3289,7 @@ static void __exit ia_module_exit(void)
> > {
> > pci_unregister_driver(&ia_driver);
> >
> > - del_timer(&ia_timer);
> > + del_timer_sync(&ia_timer);
>
> The timer is self rearming and has protection against the removal of
> the devices. So it should be fine.
>
> > }
> >
> > module_init(ia_module_init);
> > diff -u -p a/net/hsr/hsr_main.c b/net/hsr/hsr_main.c
> > --- a/net/hsr/hsr_main.c
> > +++ b/net/hsr/hsr_main.c
> > @@ -459,7 +459,7 @@ static int __init hsr_init(void)
> > static void __exit hsr_exit(void)
> > {
> > unregister_netdevice_notifier(&hsr_nb);
> > - del_timer(&prune_timer);
> > + del_timer_sync(&prune_timer);
>
> Correct as the only rearm is from the timer callback itself
>
> > hsr_netlink_exit();
> > dev_remove_pack(&hsr_pt);
> > }
> > diff -u -p a/net/atm/mpc.c b/net/atm/mpc.c
> > --- a/net/atm/mpc.c
> > +++ b/net/atm/mpc.c
> > @@ -1492,7 +1492,7 @@ static void __exit atm_mpoa_cleanup(void
> >
> > mpc_proc_clean();
> >
> > - del_timer(&mpc_timer);
> > + del_timer_sync(&mpc_timer);
>
> Looks correct as well. Timer is rearming no other dependencies.
>
> > unregister_netdevice_notifier(&mpoa_notifier);
> > deregister_atm_ioctl(&atm_ioctl_ops);
>
> Thanks,
>
> tglx
>
>
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