Re: [Xen-devel] xen/pcifront: Use monotonic clock

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 08/08/2015 09:36 PM, Abhilash Jindal wrote:
> Wall time obtained from do_gettimeofday is susceptible to sudden jumps 
> due to user setting the time or due to NTP.
> Monotonic time is constantly increasing time better suited for 
> comparing two
> timestamps.
See commit e1d5bbcdc7ca08d8731f5d780f0de342a768d96a (you probably will 
need to update your tree)
-boris

> ---
>  drivers/pci/xen-pcifront.c |   10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/pci/xen-pcifront.c b/drivers/pci/xen-pcifront.c
> index f7197a7..5ef3eb7 100644
> --- a/drivers/pci/xen-pcifront.c
> +++ b/drivers/pci/xen-pcifront.c
> @@ -114,7 +114,7 @@ static int do_pci_op(struct pcifront_device *pdev, 
> struct xen_pci_op *op)
> evtchn_port_t port = pdev->evtchn;
> unsigned irq = pdev->irq;
> s64 ns, ns_timeout;
> -struct timeval tv;
> +struct timespec tv;
> spin_lock_irqsave(&pdev->sh_info_lock, irq_flags);
> @@ -131,8 +131,8 @@ static int do_pci_op(struct pcifront_device *pdev, 
> struct xen_pci_op *op)
> * (in the latter case we end up continually re-executing poll() with a
> * timeout in the past). 1s difference gives plenty of slack for error.
> */
> -do_gettimeofday(&tv);
> -ns_timeout = timeval_to_ns(&tv) + 2 * (s64)NSEC_PER_SEC;
> +ktime_get_ts(&tv);
> +ns_timeout = timespec_to_ns(&tv) + 2 * (s64)NSEC_PER_SEC;
> xen_clear_irq_pending(irq);
> @@ -140,8 +140,8 @@ static int do_pci_op(struct pcifront_device *pdev, 
> struct xen_pci_op *op)
> (unsigned long *)&pdev->sh_info->flags)) {
> xen_poll_irq_timeout(irq, jiffies + 3*HZ);
> xen_clear_irq_pending(irq);
> -do_gettimeofday(&tv);
> -ns = timeval_to_ns(&tv);
> +ktime_get_ts(&tv);
> +ns = timespec_to_ns(&tv);
> if (ns > ns_timeout) {
> dev_err(&pdev->xdev->dev,
> "pciback not responding!!!\n");
> --
> 1.7.9.5

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