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 04/19] PCI: serialize hotplug operations triggered by PCI hotplug sysfs interfaces
Date: Wed, 2 May 2012 14:48:15 -0700 [thread overview]
Message-ID: <20120502214815.GC27281@kroah.com> (raw)
In-Reply-To: <4FA0E02F.5040901@huawei.com>
On Wed, May 02, 2012 at 03:20:15PM +0800, Jiang Liu wrote:
> On 2012-5-2 13:06, Greg KH wrote:
> >On Fri, Apr 27, 2012 at 11:16:45PM +0800, Jiang Liu wrote:
> >>+ /* Avoid deadlock with pci_hp_deregister() */
> >>+ while (!pci_hotplug_try_enter()) {
> >>+ /* Check whether the slot has been deregistered. */
> >>+ if (list_empty(&slot->slot_list)) {
> >>+ retval = -ENODEV;
> >>+ goto exit_put;
> >>+ }
> >>+ msleep(1);
> >>+ }
> >
> >Oh my.
> >
> >Wow.
> >
> >{sigh}
> >
> >ick.
> >
> >My eyes hurt.
> >
> >And your cpu load just went crazy.
> >
> >You can now handle all of the nasty emails from sysadmins asking why
> >their systems look like their load is high for no good reason.
> My bad, should use schedule_timeout_interruptible() instead of
> msleep(1) here to avoid busy waiting.
Um, no, that's not my main point here at all.
My main point is this type of loop is the wrong thing to do in the first
place.
Please redo this whole thing, as explained in my first email in this
thread.
greg k-h
next prev parent reply other threads:[~2012-05-02 21:48 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
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 [this message]
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
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