> 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. 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
