From: Greg KH <gregkh@linuxfoundation.org>
To: Jiang Liu <jiang.liu@huawei.com>
Cc: Jiang Liu <liuj97@gmail.com>, Yinghai Lu <yinghai@kernel.org>,
Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>,
Bjorn Helgaas <bhelgaas@google.com>,
Don Dutile <ddutile@redhat.com>,
Keping Chen <chenkeping@huawei.com>,
linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org
Subject: Re: [PATCH v2 02/19] PCI: introduce recursive rwsem to serialize PCI hotplug operations
Date: Wed, 2 May 2012 14:46:08 -0700 [thread overview]
Message-ID: <20120502214608.GB27281@kroah.com> (raw)
In-Reply-To: <4FA0E161.9060307@huawei.com>
On Wed, May 02, 2012 at 03:25:21PM +0800, Jiang Liu wrote:
> On 2012-5-2 13:00, Greg KH wrote:
> >On Fri, Apr 27, 2012 at 11:16:43PM +0800, Jiang Liu wrote:
> >>From: Jiang Liu<jiang.liu@huawei.com>
> >>
> >>There are multiple ways to trigger PCI hotplug requests concurrently,
> >>such as:
> >>1. Sysfs interfaces exported by the PCI core subsystem
> >>2. Sysfs interfaces exported by the PCI hotplug subsystem
> >>3. PCI hotplug events triggered by PCI Hotplug Controllers
> >>4. ACPI hotplug events for PCI host bridges
> >>5. Driver binding/unbinding events
> >>
> >>The PCI core subsystem doesn't support concurrent hotplug operations yet,
> >>so all PCI hotplug requests should be globally serialized. This patch
> >>introduces several new interfaces to serialize PCI hotplug operations.
> >>
> >>pci_hotplug_try_enter(): try to acquire write lock
> >
> >Ick, no, why would you ever want to do that?
> >
> >>pci_hotplug_enter(): acquire write lock
> >>pci_hotplug_exit(): release write lock
> >>pci_hotplug_disable(): acquire read lock
> >>pci_hotplug_enable(): release read lock
> >
> >No, the pci hotplug core should not need a rwsem, just a simple lock, if
> >that:
> > pci_hotplug_lock()
> > pci_hotplug_unlock()
> >and that's it.
> >
> >Really you should not need these functions, the pci hotplug core should
> >handle it for you, and the drivers should not care at all. That's the
> >"proper" way to fix this up, serialize stuff within the pci core, not
> >the individual drivers.
> >
> >>Today we have reproduced the issue on a real platform by using
> >>acpiphp driver. It's an IA64 platform running Suse 11SP1 (official
> >>2.6.32.12 kernel). The test script is:
> >>
> >>This issue could be reproduced on an IA64 platform with Suse 11SP1
> >>(official 2.6.32.12 kernel) and acpiphp driver.
> >
> >You do realize just how old that kernel is right? Please don't assume
> >that this kernel version is relevant to us all these years later.
> This could be reproduced with latest kernel too, such as 3.3. We
> use 2.6.32.12 because the all 3.x series kernels can't boot on
> our IA64 platform due to an issue in scheduler. We have reproduced
> similar issue on x86 platforms with 3.x kernels.
That's wonderful, and is relevant, unlike what you originally wrote.
Please always write relevant changelog comments, otherwise they are...
greg k-h
next prev parent reply other threads:[~2012-05-02 21:46 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-27 15:16 [PATCH v2 00/19] Introduce a global lock to serialize all PCI hotplug Jiang Liu
2012-04-27 15:16 ` [PATCH v2 01/19] PCI: introduce pci_bus_get()/pci_bus_put() to hide PCI implementation details Jiang Liu
2012-04-27 15:16 ` [PATCH v2 02/19] PCI: introduce recursive rwsem to serialize PCI hotplug operations Jiang Liu
2012-05-02 5:00 ` Greg KH
2012-05-02 7:25 ` Jiang Liu
2012-05-02 21:46 ` Greg KH [this message]
2012-04-27 15:16 ` [PATCH v2 03/19] PCI: replace pci_remove_rescan_mutex with the PCI hotplug lock Jiang Liu
2012-04-27 15:16 ` [PATCH v2 04/19] PCI: serialize hotplug operations triggered by PCI hotplug sysfs interfaces Jiang Liu
2012-05-02 5:06 ` Greg KH
2012-05-02 7:20 ` Jiang Liu
2012-05-02 21:48 ` Greg KH
2012-04-27 15:16 ` [PATCH v2 05/19] PCI: correctly flush workqueue when destroy pcie hotplug controller Jiang Liu
2012-05-02 5:08 ` Greg KH
2012-04-27 15:16 ` [PATCH v2 06/19] PCI: prepare for serializing hotplug operations triggered by pciehp driver Jiang Liu
2012-05-02 5:10 ` Greg KH
2012-04-27 15:16 ` [PATCH v2 07/19] PCI: serialize hotplug operaitons triggered by the " Jiang Liu
2012-04-27 15:16 ` [PATCH v2 08/19] PCI: fix two race windows when probing/removing SHPC controller Jiang Liu
2012-04-27 15:16 ` [PATCH v2 09/19] PCI: correctly flush workqueues and timer when destroy " Jiang Liu
2012-04-27 15:16 ` [PATCH v2 10/19] PCI: serialize hotplug operaitons triggered by the shpchp driver Jiang Liu
2012-04-27 15:16 ` [PATCH v2 11/19] PCI: release IO resource in error handling path in cpcihp_generic_init() Jiang Liu
2012-04-27 15:16 ` [PATCH v2 12/19] PCI: clean up all resources in error handling path in zt5550_hc_init_one() Jiang Liu
2012-04-27 15:16 ` [PATCH v2 13/19] PCI: trivial code clean up in cpci_hotplug_core.c Jiang Liu
2012-04-27 15:16 ` [PATCH v2 14/19] PCI: fix race windows when shutting down cpcihp controller Jiang Liu
2012-04-27 15:16 ` [PATCH v2 15/19] PCI: hold a reference count to the PCI bus used by cpcihp drivers Jiang Liu
2012-04-27 15:16 ` [PATCH v2 16/19] PCI: serialize PCI hotplug operations triggered " Jiang Liu
2012-04-27 15:16 ` [PATCH v2 17/19] PCI: serialize PCI hotplug operations triggered by fakephp drivers Jiang Liu
2012-04-27 15:16 ` [PATCH v2 18/19] PCI, sysfs: Use device_type and attr_groups with pci dev Jiang Liu
2012-04-27 15:17 ` [PATCH v2 19/19] PCI: hide sys interface 'remove' and 'rescan' for SR-IOV virtual devices Jiang Liu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20120502214608.GB27281@kroah.com \
--to=gregkh@linuxfoundation.org \
--cc=bhelgaas@google.com \
--cc=chenkeping@huawei.com \
--cc=ddutile@redhat.com \
--cc=jiang.liu@huawei.com \
--cc=kaneshige.kenji@jp.fujitsu.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pci@vger.kernel.org \
--cc=liuj97@gmail.com \
--cc=yinghai@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®