Messages in this thread | | | Subject | Re: [PATCH 1/2] usbip: Remove repeated setting of hcd->state in vhci_bus_suspend() | From | shuah <> | Date | Wed, 8 May 2019 11:28:05 -0600 |
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On 5/7/19 9:49 AM, Suwan Kim wrote: > Hi Shuah, > > On Mon, May 06, 2019 at 09:13:02AM -0600, shuah wrote: >> On 5/6/19 6:55 AM, Suwan Kim wrote: >>> When hcd suspends execution, hcd_bus_suspend() calls vhci_bus_suspend() >>> which sets hcd->state as HC_STATE_SUSPENDED. But after calling >>> vhci_bus_suspend(), hcd_bus_suspend() also sets hcd->state as >>> HC_STATE_SUSPENDED. >>> So, setting hcd->state in vhci_hcd_suspend() is unnecessary. >>> >>> Signed-off-by: Suwan Kim <suwan.kim027@gmail.com> >>> --- >>> drivers/usb/usbip/vhci_hcd.c | 4 ---- >>> 1 file changed, 4 deletions(-) >>> >>> diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c >>> index 667d9c0ec905..e6f378d00fb6 100644 >>> --- a/drivers/usb/usbip/vhci_hcd.c >>> +++ b/drivers/usb/usbip/vhci_hcd.c >>> @@ -1238,10 +1238,6 @@ static int vhci_bus_suspend(struct usb_hcd *hcd) >>> dev_dbg(&hcd->self.root_hub->dev, "%s\n", __func__); >>> - spin_lock_irqsave(&vhci->lock, flags); >>> - hcd->state = HC_STATE_SUSPENDED; >>> - spin_unlock_irqrestore(&vhci->lock, flags); >>> - >>> return 0; >>> } >>> >> >> Tell me more about why you think this change is needed? How did you test >> this change? > > I think that host controller specific functions, vhci_bus_resume() > or vhci_bus_suspend() in the case of vhci, usually process host > controller specific data (struct vhci_hcd) not a generic data > (struct usb_hcd). The generic data is usually processed by generic HCD > layer. But vhci_bus_resume() and vhci_bus_suspend() set generic data > (hcd->state) and moreover this variable is set in generic HCD layer > once again(hcd_bus_resume() and hcd_bus_suspend()). > > So, i think host controller specific functions (vhci_bus_resume() > and vhci_bus_suspend()) don't need to set the generic data that is > "hcd->state = HC_STATE_RUNNING or HC_STATE_SUSPEND". >
It depends. In this case, vhci_hcd is virtual driver and maintains port status for devices that are remote. It checks hcd->state in vhci_hub_status().
It updates the hcd->state in suspend with vhci->lock hold and checks status from vhci_hub_status(). Removing updating hcd->state from vhci_bus_suspend()will open a window where vhci_hub_status() might find it wrong state.
Same thing for HC_STATE_RUNNING. There are few other drivers that do the same for similar reasons. xhci_hcd, and dummy_hcd and a few more. This is the same comment on your patch that removes HC_STATE_RUNNING update from resume.
> For test, I loaded vhci-hcd module, suspended and resumed my computer > and checked hcd->state variable. There is no difference compared with > not modified version because my patch just removes repeated and > unnecessary part. >
This won't fully test the condition since there are remote devices attached and triggering suspend while attach/detach is in progress.
thanks, -- Shuah
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