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 <jgross@suse.com>
---
V2:
- new patch, fixing FreeBSD performance issue
---
 drivers/net/xen-netback/interface.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index acb786d8b1d8..e02a4fbb74de 100644
--- 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, &queue->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, &queue->eoi_pending);
 		xen_irq_lateeoi(irq, XEN_EOI_FLAG_SPURIOUS);
 	}
-- 
2.26.2

> -----Original Message-----
> From: Juergen Gross <jgross@suse.com>
> Sent: 11 February 2021 10:16
> To: xen-devel@lists.xenproject.org; netdev@vger.kernel.org; linux-kernel@vger.kernel.org
> Cc: Juergen Gross <jgross@suse.com>; Wei Liu <wei.liu@kernel.org>; Paul Durrant <paul@xen.org>; David
> S. Miller <davem@davemloft.net>; Jakub Kicinski <kuba@kernel.org>
> 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 <jgross@suse.com>

Reviewed-by: Paul Durrant <paul@xen.org>

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 <jgross@suse.com>

Reviewed-by: Wei Liu <wl@xen.org>

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, &queue->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, &queue->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 <jbeulich@suse.com>

Jan