[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <20061028094931.65a0f218.akpm@osdl.org>
Date: Sat, 28 Oct 2006 09:49:31 -0700
From: Andrew Morton <akpm@...l.org>
To: Ravikiran G Thirumalai <kiran@...lex86.org>
Cc: linux-kernel@...r.kernel.org,
Christoph Lameter <clameter@...r.sgi.com>,
Pekka J Enberg <penberg@...Helsinki.FI>, ego@...ibm.com,
vatsa@...ibm.com,
"Benzi Galili (Benzi@...leMP.com)" <benzi@...lemp.com>,
Alok Kataria <alok.kataria@...softinc.com>, shai@...lex86.org
Subject: Re: [rfc] [patch] mm: Slab - Eliminate lock_cpu_hotplug from slab
On Fri, 27 Oct 2006 18:19:19 -0700
Ravikiran G Thirumalai <kiran@...lex86.org> wrote:
> Another note. Looks like a cpu hotplug event can send CPU_UP_CANCELED to
> a registered subsystem even if the subsystem did not receive CPU_UP_PREPARE.
> This could be due to a subsystem registered for notification earlier than
> the current subsystem crapping out with NOTIFY_BAD. Badness can occur with
> in the CPU_UP_CANCELED code path at slab if this happens (The same would
> apply for workqueue.c as well).
yup, cancellation doesn't work at present.
> To overcome this, we might have to use either
> a) a per subsystem flag and avoid handling of CPU_UP_CANCELED, or
> b) Use a special notifier events like LOCK_ACQUIRE/RELEASE as Gautham was
> using in his experiments, or
> c) Do not send CPU_UP_CANCELED to a subsystem which did not receive
> CPU_UP_PREPARE.
>
> I would prefer c).
c) would work. I guess we could do that by simply counting the number of
called handlers rather than having to record state within each one.
It would require changes to the notifier_chain API, but I think the changes
are needed - the problem is general. Something like:
int __raw_notifier_call_chain(struct raw_notifier_head *nh,
unsigned long val, void *v, unsigned nr_to_call, int *nr_called);
int raw_notifier_call_chain(struct raw_notifier_head *nh,
unsigned long val, void *v)
{
return __raw_notifier_call_chain(nh, val, v, -1, NULL);
}
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists