On Thu, Nov 21, 2019 at 12:50:17AM +0000, Dexuan Cui wrote: > > From: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx> > > 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
