From: Philipp Rumpf <prumpf@mandrakesoft.com>
To: Keith Owens <kaos@ocs.com.au>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>, linux-kernel@vger.kernel.org
Subject: Re: Linux 2.4.1-ac15
Date: Mon, 19 Feb 2001 06:15:22 -0600 (CST) [thread overview]
Message-ID: <Pine.LNX.3.96.1010219055750.16489G-100000@mandrakesoft.mandrakesoft.com> (raw)
In-Reply-To: <30069.982583679@ocs3.ocs-net>
On Mon, 19 Feb 2001, Keith Owens wrote:
> On Mon, 19 Feb 2001 11:35:08 +0000 (GMT),
> Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
> >The problem isnt running module code. What happens in this case
> >
> > mod->next = module_list;
> > module_list = mod; /* link it in */
> >
> >Note no write barrier.
>
> <humour>It works on ix86 so the code must be right</humour>
Too bad it doesn't.
> >Delete is even worse
> >
> >We unlink the module
> >We free the memory
> >
> >At the same time another cpu may be walking the exception table that we free.
>
> Another good reason why locking modules via use counts from external
> code is not the right fix. We definitely need a quiesce model for
> module removal.
Unless I'm mistaken, we need both use counts and SMP magic (though not
necessarily as extreme as what the "freeze all other CPUs during module
unload" patch did).
I think something like this would work (in addition to use counts)
int callin_func(void *p)
{
int *cpu = p;
while (*cpu != smp_processor_id()) {
current->cpus_allowed = 1 << *cpu;
schedule();
}
return 0;
}
void callin_other_cpus(void)
{
int cpus[smp_num_cpus];
int i;
for (i=0; i<smp_num_cpus; i++) {
cpus[i] = i;
kernel_thread(callin_func, &cpus[i], ...);
}
}
and call callin_other_cpus() before unloading a module.
I'm not sure how you could make exception handling safe without locking
all accesses to the module list - but that sounds like the sane thing to
do anyway.
next prev parent reply other threads:[~2001-02-19 12:18 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-02-15 23:15 Linux 2.4.1-ac15 Alan Cox
2001-02-19 9:47 ` Philipp Rumpf
2001-02-19 11:35 ` Alan Cox
2001-02-19 11:54 ` Philipp Rumpf
2001-02-19 16:03 ` Alan Cox
2001-02-19 16:21 ` Philipp Rumpf
2001-02-19 16:27 ` Alan Cox
2001-02-19 16:34 ` Philipp Rumpf
2001-02-19 16:41 ` Alan Cox
2001-02-19 16:48 ` Philipp Rumpf
2001-02-19 17:03 ` Alan Cox
2001-02-21 3:02 ` Rusty Russell
2001-02-21 12:01 ` Alan Cox
2001-02-22 2:05 ` Rusty Russell
2001-02-22 10:22 ` Alan Cox
2001-02-23 0:01 ` Philipp Rumpf
2001-02-22 2:27 ` Linus Torvalds
2001-02-22 10:29 ` Alan Cox
2001-02-23 20:40 ` Andrea Arcangeli
2001-02-23 21:09 ` Linus Torvalds
2001-02-24 4:04 ` Andrea Arcangeli
2001-02-24 4:54 ` Andrea Arcangeli
2001-02-19 11:54 ` Keith Owens
2001-02-19 12:15 ` Philipp Rumpf [this message]
2001-02-19 13:15 ` Keith Owens
2001-02-19 13:25 ` Christoph Hellwig
2001-02-19 21:32 ` Keith Owens
2001-02-19 13:36 ` Philipp Rumpf
2001-02-19 15:23 ` Manfred Spraul
2001-02-19 16:04 ` Alan Cox
2001-02-19 21:52 ` Keith Owens
2001-02-20 12:29 ` Philipp Rumpf
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