Messages in this thread | | | Subject | Re: [PATCH] usbip: vhci_hcd: slighly simplify code in 'vhci_urb_dequeue()' | From | shuah <> | Date | Mon, 23 Mar 2020 10:48:33 -0600 |
| |
On 3/21/20 9:29 AM, Christophe JAILLET wrote: > The allocation of 'unlink' can be moved before a spin_lock. > This slighly simplifies the error handling if the memory allocation fails,
slightly (spelling nit)
> aligns the code structure with what is done in 'vhci_tx_urb()' and reduces > potential lock contention. >
Are you seeing any problems or is this a potential lock contention? If you are seeing issues, please share the problem seen.
> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr> > --- > drivers/usb/usbip/vhci_hcd.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c > index 65850e9c7190..b909a634260c 100644 > --- a/drivers/usb/usbip/vhci_hcd.c > +++ b/drivers/usb/usbip/vhci_hcd.c > @@ -905,17 +905,16 @@ static int vhci_urb_dequeue(struct usb_hcd *hcd, struct urb *urb, int status) > /* tcp connection is alive */ > struct vhci_unlink *unlink; > > - spin_lock(&vdev->priv_lock); > -
This change might simplify the error path, however it could open a race window with the unlink activity during vhci_shutdown_connection() when the connection is being taken down. It would be safer to hold both locks as soon as the connection check is done.
> /* setup CMD_UNLINK pdu */ > unlink = kzalloc(sizeof(struct vhci_unlink), GFP_ATOMIC); > if (!unlink) { > - spin_unlock(&vdev->priv_lock); > spin_unlock_irqrestore(&vhci->lock, flags); > usbip_event_add(&vdev->ud, VDEV_EVENT_ERROR_MALLOC); > return -ENOMEM; > } > > + spin_lock(&vdev->priv_lock); > + > unlink->seqnum = atomic_inc_return(&vhci_hcd->seqnum); > if (unlink->seqnum == 0xffff) > pr_info("seqnum max\n"); >
thanks, -- Shuah
| |