From: Dexuan Cui <decui@xxxxxxxxxxxxx> Sent: Sunday, November 24, 2019 9:34 PM > > Add suspend() and resume() functions so that Hyper-V virtual PCI devices are > handled properly when the VM hibernates and resumes from hibernation. > > Note that the suspend() function must make sure there are no pending work > items before calling vmbus_close(), since it 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. > > Signed-off-by: Dexuan Cui <decui@xxxxxxxxxxxxx> Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
