From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: Vasilis Liaskovitis <vasilis.liaskovitis@profitbricks.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Toshi Kani <toshi.kani@hp.com>,
ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
isimatu.yasuaki@jp.fujitsu.com, Len Brown <lenb@kernel.org>,
linux-mm@kvack.org
Subject: Re: [PATCH 2/2 v2, RFC] Driver core: Introduce offline/online callbacks for memory blocks
Date: Tue, 07 May 2013 02:59:05 +0200 [thread overview]
Message-ID: <1809544.1r1JBXrr0i@vostro.rjw.lan> (raw)
In-Reply-To: <20130506162812.GB4929@dhcp-192-168-178-175.profitbricks.localdomain>
On Monday, May 06, 2013 06:28:12 PM Vasilis Liaskovitis wrote:
> Hi,
>
> On Sat, May 04, 2013 at 01:21:16PM +0200, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> >
> > Introduce .offline() and .online() callbacks for memory_subsys
> > that will allow the generic device_offline() and device_online()
> > to be used with device objects representing memory blocks. That,
> > in turn, allows the ACPI subsystem to use device_offline() to put
> > removable memory blocks offline, if possible, before removing
> > memory modules holding them.
> >
> > The 'online' sysfs attribute of memory block devices will attempt to
> > put them offline if 0 is written to it and will attempt to apply the
> > previously used online type when onlining them (i.e. when 1 is
> > written to it).
> >
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> > ---
> > drivers/base/memory.c | 105 +++++++++++++++++++++++++++++++++++++------------
> > include/linux/memory.h | 1
> > 2 files changed, 81 insertions(+), 25 deletions(-)
> >
> [...]
>
> > @@ -686,10 +735,16 @@ int offline_memory_block(struct memory_b
> > {
> > int ret = 0;
> >
> > + lock_device_hotplug();
> > mutex_lock(&mem->state_mutex);
> > - if (mem->state != MEM_OFFLINE)
> > - ret = __memory_block_change_state(mem, MEM_OFFLINE, MEM_ONLINE, -1);
> > + if (mem->state != MEM_OFFLINE) {
> > + ret = __memory_block_change_state_uevent(mem, MEM_OFFLINE,
> > + MEM_ONLINE, -1);
> > + if (!ret)
> > + mem->dev.offline = true;
> > + }
> > mutex_unlock(&mem->state_mutex);
> > + unlock_device_hotplug();
>
> (Testing with qemu...)
Thanks!
> offline_memory_block is called from remove_memory, which in turn is called from
> acpi_memory_device_remove (detach operation) during acpi_bus_trim. We already
> hold the device_hotplug lock when we trim (acpi_scan_hot_remove), so we
> don't need to lock/unlock_device_hotplug in offline_memory_block.
Indeed.
First, it looks like offline_memory_block_cb() is the only place calling
offline_memory_block(), is that right? I'm wondering if it would make
sense to use device_offline() in there and remove offline_memory_block()
entirely?
Second, if you ran into this issue during testing, that would mean that patch
[1/2] actually worked for you, which would be nice. :-) Was that really the
case?
> A more general issue is that there are now two memory offlining efforts:
>
> 1) from acpi_bus_offline_companions during device offline
> 2) from mm: remove_memory during device detach (offline_memory_block_cb)
>
> The 2nd is only called if the device offline operation was already succesful, so
> it seems ineffective or redundant now, at least for x86_64/acpi_memhotplug machine
> (unless the blocks were re-onlined in between).
Sure, and that should be OK for now. Changing the detach behavior is not
essential from the patch [2/2] perspective, we can do it later.
> On the other hand, the 2nd effort has some more intelligence in offlining, as it
> tries to offline twice in the precense of memcg, see commits df3e1b91 or
> reworked 0baeab16. Maybe we need to consolidate the logic.
Hmm. Perhaps it would make sense to implement that logic in
memory_subsys_offline(), then?
> remove_memory is called from device_detach, during trim that can't fail, so it
> should not fail. However this function can still fail in 2 cases:
> - offline_memory_block_cb
> - is_memblock_offlined_cb
> in the case of re-onlined memblocks in between device-offline and device detach.
> This seems possible I think, since we do not hold lock_memory_hotplug for the
> duration of the hot-remove operation.
But we do hold device_hotplug_lock, so every code path that may race with
acpi_scan_hot_remove() needs to take device_hotplug_lock as well. Now,
question is whether or not there are any code paths like that calling one of
the two functions above without holding device_hotplug_lock?
Rafael
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
next prev parent reply other threads:[~2013-05-07 0:50 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-29 12:23 [PATCH 0/3 RFC] Driver core / ACPI: Add offline/online for graceful hot-removal of devices Rafael J. Wysocki
2013-04-29 12:26 ` [PATCH 1/3 RFC] Driver core: Add offline/online device operations Rafael J. Wysocki
2013-04-29 23:10 ` Greg Kroah-Hartman
2013-04-30 11:59 ` Rafael J. Wysocki
2013-04-30 15:32 ` Greg Kroah-Hartman
2013-04-30 20:05 ` Rafael J. Wysocki
2013-04-30 23:38 ` Toshi Kani
2013-05-02 0:58 ` Rafael J. Wysocki
2013-05-02 23:29 ` Toshi Kani
2013-05-03 11:48 ` Rafael J. Wysocki
2013-04-29 12:28 ` [PATCH 2/3 RFC] Driver core: Use generic offline/online for CPU offline/online Rafael J. Wysocki
2013-04-29 23:11 ` Greg Kroah-Hartman
2013-04-30 12:01 ` Rafael J. Wysocki
2013-04-30 15:27 ` Greg Kroah-Hartman
2013-04-30 20:06 ` Rafael J. Wysocki
2013-04-30 23:42 ` Toshi Kani
2013-05-01 14:49 ` Rafael J. Wysocki
2013-05-01 20:07 ` Toshi Kani
2013-05-02 0:26 ` Rafael J. Wysocki
2013-04-29 12:29 ` [PATCH 3/3 RFC] ACPI / hotplug: Use device offline/online for graceful hot-removal Rafael J. Wysocki
2013-04-30 23:49 ` Toshi Kani
2013-05-01 15:05 ` Rafael J. Wysocki
2013-05-01 20:20 ` Toshi Kani
2013-05-02 0:53 ` Rafael J. Wysocki
2013-05-02 12:26 ` [PATCH 0/4] Driver core / ACPI: Add offline/online for graceful hot-removal of devices Rafael J. Wysocki
2013-05-02 12:27 ` [PATCH 1/4] Driver core: Add offline/online device operations Rafael J. Wysocki
2013-05-02 13:57 ` Greg Kroah-Hartman
2013-05-02 23:11 ` Toshi Kani
2013-05-02 23:36 ` Rafael J. Wysocki
2013-05-02 23:23 ` Toshi Kani
2013-05-02 12:28 ` [PATCH 2/4] Driver core: Use generic offline/online for CPU offline/online Rafael J. Wysocki
2013-05-02 13:57 ` Greg Kroah-Hartman
2013-05-02 12:29 ` [PATCH 3/4] ACPI / hotplug: Use device offline/online for graceful hot-removal Rafael J. Wysocki
2013-05-02 12:31 ` [PATCH 4/4] ACPI / processor: Use common hotplug infrastructure Rafael J. Wysocki
2013-05-02 13:59 ` Greg Kroah-Hartman
2013-05-02 23:20 ` Toshi Kani
2013-05-03 12:05 ` Rafael J. Wysocki
2013-05-03 12:21 ` Rafael J. Wysocki
2013-05-03 18:27 ` Toshi Kani
2013-05-03 19:31 ` Rafael J. Wysocki
2013-05-03 19:34 ` Toshi Kani
2013-05-04 1:01 ` [PATCH 0/3 RFC] Driver core: Add offline/online callbacks for memory_subsys Rafael J. Wysocki
2013-05-04 1:03 ` [PATCH 1/3 RFC] ACPI / memhotplug: Bind removable memory blocks to ACPI device nodes Rafael J. Wysocki
2013-05-04 1:04 ` [PATCH 2/3 RFC] Driver core: Introduce types of device "online" Rafael J. Wysocki
2013-05-04 1:06 ` [PATCH 3/3 RFC] Driver core: Introduce offline/online callbacks for memory blocks Rafael J. Wysocki
2013-05-04 11:11 ` [PATCH 0/2 v2, RFC] Driver core: Add offline/online callbacks for memory_subsys Rafael J. Wysocki
2013-05-04 11:12 ` [PATCH 1/2 v2, RFC] ACPI / memhotplug: Bind removable memory blocks to ACPI device nodes Rafael J. Wysocki
2013-05-21 6:50 ` Tang Chen
2013-05-04 11:21 ` [PATCH 2/2 v2, RFC] Driver core: Introduce offline/online callbacks for memory blocks Rafael J. Wysocki
2013-05-06 16:28 ` Vasilis Liaskovitis
2013-05-07 0:59 ` Rafael J. Wysocki [this message]
2013-05-07 10:59 ` Vasilis Liaskovitis
2013-05-07 12:11 ` Rafael J. Wysocki
2013-05-07 21:03 ` Toshi Kani
2013-05-07 22:10 ` Rafael J. Wysocki
2013-05-07 22:45 ` Toshi Kani
2013-05-07 23:17 ` Rafael J. Wysocki
2013-05-07 23:59 ` Toshi Kani
2013-05-08 0:24 ` Rafael J. Wysocki
2013-05-08 0:37 ` Toshi Kani
2013-05-08 11:53 ` Rafael J. Wysocki
2013-05-08 14:38 ` Toshi Kani
2013-05-06 17:20 ` Greg Kroah-Hartman
2013-05-06 19:46 ` Rafael J. Wysocki
2013-05-21 6:37 ` Tang Chen
2013-05-21 11:15 ` Rafael J. Wysocki
2013-05-22 4:45 ` Tang Chen
2013-05-22 10:42 ` Rafael J. Wysocki
2013-05-22 22:06 ` [PATCH] Driver core / memory: Simplify __memory_block_change_state() Rafael J. Wysocki
2013-05-22 22:14 ` Greg Kroah-Hartman
2013-05-22 23:29 ` Rafael J. Wysocki
2013-05-23 4:37 ` Tang Chen
2013-05-06 10:48 ` [PATCH 0/2 v2, RFC] Driver core: Add offline/online callbacks for memory_subsys Rafael J. Wysocki
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