From: Thomas Gleixner <tglx@linutronix.de>
To: Julia Lawall <julia.lawall@lip6.fr>
Cc: LKML <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [patch 00/16] timers: Plug debugobject leaks and use del_timer_sync() in exit/teardown
Date: Mon, 24 Mar 2014 00:37:52 +0100 (CET) [thread overview]
Message-ID: <alpine.DEB.2.02.1403240027020.18573@ionos.tec.linutronix.de> (raw)
In-Reply-To: <alpine.DEB.2.02.1403232328480.2019@localhost6.localdomain6>
On Sun, 23 Mar 2014, Julia Lawall wrote:
> As far as I could tell, (part of) the issue is that any kind of exit or
> close function should use del_timer_sync, because they could be called
> from a different CPU than the one that started up the timer?
>
> Here is a semantic patch that takes care of the case of simple module_exit
> functions:
>
> @r@
> declarer name module_exit;
> identifier ex;
> @@
>
> module_exit(ex);
>
> @@
> identifier r.ex;
> @@
>
> ex(...) {
> <...
> - del_timer
> + del_timer_sync
> (...)
> ...>
> }
>
> The transformations it makes are below. I haven't had a chance to check
> which results overlap with what Thomas has already sent, but I could look
Minimal overlap, but as I said I did just a few conversions.
> into it if this is the right idea. I guess other kinds of close/exit
> functions would have to be identified manually, to make more rules.
If you look through the examples I sent, you'll find the close()
callbacks of various devices. So everything which is a function
pointer to a ops->close(), ops->remove(), ops_>teardown() is dangerous
if using del_timer(). There are a few exceptions, but....
Another thing I saw is
del_timer(&bla->timer);
....
kfree(&bla);
That's also a potential source of trouble. You can't tell without
analyzing the code, whether it's a problem or not. But making the
responsible people to look at it is definitely a good thing.
> In what circumstance can one be sure that two instructions are executed on
> the same CPU?
If interrupts or preemption are disabled. But that's not the issue at
hand.
The del_timer vs. del_timer_sync problem is:
CPU0 CPU1
add_timer(&bla->timer);
close(bla)
timer expires del_timer(&bla->timer);
callback is invoked
kfree(bla);
derefernces bla
I'll look at your findings on Tuesday, but feel free to send them to
the relevant maintainers for review.
Thanks,
tglx
next prev parent reply other threads:[~2014-03-23 23:37 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-23 15:09 [patch 00/16] timers: Plug debugobject leaks and use del_timer_sync() in exit/teardown Thomas Gleixner
2014-03-23 15:09 ` [patch 01/16] s390: tape: Use del_timer_sync() Thomas Gleixner
2014-03-24 6:22 ` Heiko Carstens
2014-03-23 15:09 ` [patch 03/16] s390: net: lcs: Add missing destroy_timer_on_stack() Thomas Gleixner
2014-03-24 6:22 ` Heiko Carstens
2014-03-23 15:09 ` [patch 02/16] s390: tape: " Thomas Gleixner
2014-03-24 6:22 ` Heiko Carstens
2014-03-23 15:09 ` [patch 04/16] scsi: qla1280: " Thomas Gleixner
2014-03-23 15:09 ` [patch 05/16] thermal: powerclamp: " Thomas Gleixner
2014-03-23 15:09 ` [patch 06/16] rcu: torture: " Thomas Gleixner
2014-03-23 16:01 ` Paul E. McKenney
2014-03-23 18:13 ` Josh Triplett
2014-03-23 15:09 ` [patch 08/16] atm: idt77105: Use del_timer_sync() in exit path Thomas Gleixner
2014-03-26 1:06 ` David Miller
2014-03-23 15:09 ` [patch 07/16] atm: firestream: Use del_timer_sync() in teardown path Thomas Gleixner
2014-03-26 1:06 ` David Miller
2014-03-23 15:09 ` [patch 10/16] block: umem: Use del_timer_sync() in exit path Thomas Gleixner
2014-03-23 15:09 ` [patch 09/16] block: cpqarray: Use del_timer_sync() in teardown Thomas Gleixner
2014-03-23 15:09 ` [patch 11/16] block: xsysace; Use del_timer_sync() in exit path Thomas Gleixner
2014-03-23 15:09 ` [patch 12/16] bt: bluecard: Use del_timer_sync() in teardown path Thomas Gleixner
2014-03-23 15:09 ` Thomas Gleixner
2014-03-23 17:30 ` Marcel Holtmann
2014-03-23 15:09 ` [patch 13/16] bt: hci-bcsp: " Thomas Gleixner
2014-03-23 15:09 ` Thomas Gleixner
2014-03-23 17:30 ` Marcel Holtmann
2014-03-23 15:09 ` [patch 14/16] bt: hci-h5: Use del_timer_sync() in exit path Thomas Gleixner
2014-03-23 15:09 ` Thomas Gleixner
2014-03-23 17:30 ` Marcel Holtmann
2014-03-23 15:09 ` [patch 15/16] cpufreq: intel-pstate: Use del_timer_sync in intel_pstate_cpu_exit() Thomas Gleixner
2014-03-24 1:56 ` Rafael J. Wysocki
2014-03-24 14:18 ` Dirk Brandewie
2014-03-24 4:45 ` Viresh Kumar
2014-03-23 15:09 ` [patch 16/16] input: serio: hp_sdc: Use del_timer_sync() in exit path Thomas Gleixner
2014-03-24 0:24 ` Dmitry Torokhov
2014-03-23 22:34 ` [patch 00/16] timers: Plug debugobject leaks and use del_timer_sync() in exit/teardown Julia Lawall
2014-03-23 23:37 ` Thomas Gleixner [this message]
2014-03-24 6:50 ` Julia Lawall
2014-03-24 7:29 ` Julia Lawall
2014-03-24 9:03 ` Thomas Gleixner
2014-03-25 21:08 ` Thomas Gleixner
2014-03-25 21:19 ` Julia Lawall
2014-03-26 18:53 ` Julia Lawall
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