Re: [PATCH v2 4/8] xen/netback: fix spurious event detection for common event case
On Thu, Feb 11, 2021 at 11:16:12AM +0100, Juergen Gross wrote:
> In case of a common event for rx and tx queue the event should be
> regarded to be spurious if no rx and no tx requests are pending.
>
> Unfortunately the condition for testing that is wrong causing to
> decide a event being spurious if no rx OR no tx requests are
> pending.
>
> Fix that plus using local variables for rx/tx pending indicators in
> order to split function calls and if condition.
>
> Fixes: 23025393dbeb3b ("xen/netback: use lateeoi irq binding")
> Signed-off-by: Juergen Gross
Reviewed-by: Wei Liu
RE: [PATCH v2 4/8] xen/netback: fix spurious event detection for common event case
> -Original Message-
> From: Juergen Gross
> Sent: 11 February 2021 10:16
> To: xen-de...@lists.xenproject.org; net...@vger.kernel.org;
> linux-kernel@vger.kernel.org
> Cc: Juergen Gross ; Wei Liu ; Paul
> Durrant ; David
> S. Miller ; Jakub Kicinski
> Subject: [PATCH v2 4/8] xen/netback: fix spurious event detection for common
> event case
>
> In case of a common event for rx and tx queue the event should be
> regarded to be spurious if no rx and no tx requests are pending.
>
> Unfortunately the condition for testing that is wrong causing to
> decide a event being spurious if no rx OR no tx requests are
> pending.
>
> Fix that plus using local variables for rx/tx pending indicators in
> order to split function calls and if condition.
>
Definitely neater.
> Fixes: 23025393dbeb3b ("xen/netback: use lateeoi irq binding")
> Signed-off-by: Juergen Gross
Reviewed-by: Paul Durrant
Re: [PATCH v2 4/8] xen/netback: fix spurious event detection for common event case
On 11.02.2021 11:16, Juergen Gross wrote:
> --- a/drivers/net/xen-netback/interface.c
> +++ b/drivers/net/xen-netback/interface.c
> @@ -162,13 +162,15 @@ irqreturn_t xenvif_interrupt(int irq, void *dev_id)
> {
> struct xenvif_queue *queue = dev_id;
> int old;
> + bool has_rx, has_tx;
>
> old = atomic_fetch_or(NETBK_COMMON_EOI, >eoi_pending);
> WARN(old, "Interrupt while EOI pending\n");
>
> - /* Use bitwise or as we need to call both functions. */
> - if ((!xenvif_handle_tx_interrupt(queue) |
> - !xenvif_handle_rx_interrupt(queue))) {
> + has_tx = xenvif_handle_tx_interrupt(queue);
> + has_rx = xenvif_handle_rx_interrupt(queue);
> +
> + if (!has_rx && !has_tx) {
> atomic_andnot(NETBK_COMMON_EOI, >eoi_pending);
> xen_irq_lateeoi(irq, XEN_EOI_FLAG_SPURIOUS);
> }
>
Ah yes, what was originally meant really was
if (!(xenvif_handle_tx_interrupt(queue) |
xenvif_handle_rx_interrupt(queue))) {
(also hinted at by the otherwise pointless inner parentheses),
which you simply write in an alternative way.
Reviewed-by: Jan Beulich
Jan
