From: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
To: Dexuan Cui <decui@microsoft.com>
Cc: KY Srinivasan <kys@microsoft.com>,
Haiyang Zhang <haiyangz@microsoft.com>,
Stephen Hemminger <sthemmin@microsoft.com>,
"sashal@kernel.org" <sashal@kernel.org>,
"bhelgaas@google.com" <bhelgaas@google.com>,
"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Michael Kelley <mikelley@microsoft.com>,
Sasha Levin <Alexander.Levin@microsoft.com>
Subject: Re: [PATCH v2 2/4] PCI: hv: Add the support of hibernation
Date: Thu, 21 Nov 2019 11:44:19 +0000 [thread overview]
Message-ID: <20191121114419.GA4318@e121166-lin.cambridge.arm.com> (raw)
In-Reply-To: <PU1P153MB0169D0A99D5687FBDB02536BBF4E0@PU1P153MB0169.APCP153.PROD.OUTLOOK.COM>
On Thu, Nov 21, 2019 at 12:50:17AM +0000, Dexuan Cui wrote:
> > From: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> > Sent: Wednesday, November 20, 2019 9:20 AM
> >
> > On Tue, Nov 19, 2019 at 11:16:56PM -0800, Dexuan Cui wrote:
> > > Implement the suspend/resume callbacks.
> > >
> > > We must make sure there is no pending work items before we call
> > > vmbus_close().
> >
> > Where ? Why ? Imagine a developer reading this log to try to understand
> > why you made this change, do you really think this commit log is
> > informative in its current form ?
> >
> > I am not asking a book but this is a significant feature please make
> > an effort to explain it (I can update the log for you but please
> > write one and I shall do it).
> >
> > Lorenzo
>
> Sorry for being sloppy on this patch's changelog! Can you please use the
> below? I can also post v3 with the new changelog if that's better.
As you wish but more importantly get hyper-V maintainers to ACK these
changes since time is running out for v5.5.
Lorenzo
> PCI: hv: Add the support of hibernation
>
> hv_pci_suspend() runs in a process context as a callback in dpm_suspend().
> When it starts to run, the channel callback hv_pci_onchannelcallback(),
> which runs in a tasklet context, can be still running concurrently and
> scheduling new work items onto hbus->wq in hv_pci_devices_present() and
> hv_pci_eject_device(), and the work item handlers can access the vmbus
> channel, which can be being closed by hv_pci_suspend(), e.g. the work item
> handler pci_devices_present_work() -> new_pcichild_device() writes to
> the vmbus channel.
>
> To eliminate the race, hv_pci_suspend() disables the channel callback
> tasklet, sets hbus->state to hv_pcibus_removing, and re-enables the tasklet.
>
> This way, when hv_pci_suspend() proceeds, it knows that no new work item
> can be scheduled, and then it flushes hbus->wq and safely closes the vmbus
> channel.
>
> Thanks,
> -- Dexuan
next prev parent reply other threads:[~2019-11-21 11:44 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-20 7:16 [PATCH v2 0/4] Enhance pci-hyperv to support hibernation, and 2 misc fixes Dexuan Cui
2019-11-20 7:16 ` [PATCH v2 1/4] PCI: hv: Reorganize the code in preparation of hibernation Dexuan Cui
2019-11-24 22:21 ` Michael Kelley
2019-11-20 7:16 ` [PATCH v2 2/4] PCI: hv: Add the support " Dexuan Cui
2019-11-20 17:20 ` Lorenzo Pieralisi
2019-11-21 0:50 ` Dexuan Cui
2019-11-21 11:44 ` Lorenzo Pieralisi [this message]
2019-11-24 22:19 ` Michael Kelley
2019-11-25 10:44 ` Lorenzo Pieralisi
2019-11-20 7:16 ` [PATCH v2 3/4] PCI: hv: Change pci_protocol_version to per-hbus Dexuan Cui
2019-11-24 22:00 ` Michael Kelley
2019-11-20 7:16 ` [PATCH v2 4/4] PCI: hv: kmemleak: Track the page allocations for struct hv_pcibus_device Dexuan Cui
2019-11-20 17:12 ` Lorenzo Pieralisi
2019-11-21 0:53 ` Dexuan Cui
2019-11-24 21:52 ` Michael Kelley
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