| Message ID | 20190506125550.7826-1-suwan.kim027@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/2] usbip: Remove repeated setting of hcd->state in vhci_bus_suspend() | expand |
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? thanks, -- Shuah
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". 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. Regards Suwan Kim
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
On Wed, May 08, 2019 at 11:28:05AM -0600, shuah wrote: > 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. > I didn't know that and I missed. Thank you for pointing out my fault. I agree that removing updating hcd->state which is protected by vhci lock is not correct. But I still have not fully understood the relationship between vhci_bus_suspend() and vhci_hub_status() yet. I will look at it in more detail. Again, thank you for reviewing my patch. Regards Suwan Kim
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; }
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(-)