[v1] net/mlx4: return EAGAIN on premature disable interrupt calls
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Commit Message
RXQ interrupts under Linux are based on the epoll mechanism. An
expected order of operations is as follows:
1. Call rte_eth_dev_rx_intr_enable(), to arm the CQ for receiving events
on data input.
2. Block on rte_epoll_wait() with an array of file descriptors
representing the CQ events. Upon data arrival the kernel will signal an
input event on the corresponding CQ fd.
3. Call rte_eth_dev_rx_intr_disable() after the event was received and
continue in polling mode. The mlx4 implementation of
rte_eth_dev_rx_intr_disable() is to get the CQ event and ack it.
In practice applications may wake up from rte_epoll_wait() due to
timeout with no event to ack but still call
rte_eth_dev_rx_intr_disable() unconditionally. In such cases the call
should return EAGAIN (since the file descriptors are non-blocked), as
opposed to EINVAL which indicates a real failure. In case of EAGAIN the
PMD should not warn on "unable to disable interrupt on rx queue".
Signed-off-by: Ophir Munk <ophirmu@mellanox.com>
---
drivers/net/mlx4/mlx4_intr.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
Comments
Hi,
> -----Original Message-----
> From: Ophir Munk <ophirmu@mellanox.com>
> Sent: Tuesday, July 28, 2020 2:54 PM
> To: dev@dpdk.org
> Cc: Raslan Darawsheh <rasland@mellanox.com>; Ophir Munk
> <ophirmu@mellanox.com>; Matan Azrad <matan@mellanox.com>
> Subject: [PATCH v1] net/mlx4: return EAGAIN on premature disable interrupt
> calls
>
> RXQ interrupts under Linux are based on the epoll mechanism. An
> expected order of operations is as follows:
> 1. Call rte_eth_dev_rx_intr_enable(), to arm the CQ for receiving events
> on data input.
> 2. Block on rte_epoll_wait() with an array of file descriptors
> representing the CQ events. Upon data arrival the kernel will signal an
> input event on the corresponding CQ fd.
> 3. Call rte_eth_dev_rx_intr_disable() after the event was received and
> continue in polling mode. The mlx4 implementation of
> rte_eth_dev_rx_intr_disable() is to get the CQ event and ack it.
>
> In practice applications may wake up from rte_epoll_wait() due to
> timeout with no event to ack but still call
> rte_eth_dev_rx_intr_disable() unconditionally. In such cases the call
> should return EAGAIN (since the file descriptors are non-blocked), as
> opposed to EINVAL which indicates a real failure. In case of EAGAIN the
> PMD should not warn on "unable to disable interrupt on rx queue".
>
> Signed-off-by: Ophir Munk <ophirmu@mellanox.com>
Acked-by: Raslan Darawsheh <rasland@mellanox.com>
> ---
> drivers/net/mlx4/mlx4_intr.c | 13 ++++++++++---
> 1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/mlx4/mlx4_intr.c b/drivers/net/mlx4/mlx4_intr.c
> index 020fc25..19af935 100644
> --- a/drivers/net/mlx4/mlx4_intr.c
> +++ b/drivers/net/mlx4/mlx4_intr.c
> @@ -326,13 +326,20 @@ mlx4_rx_intr_disable(struct rte_eth_dev *dev,
> uint16_t idx)
> } else {
> ret = mlx4_glue->get_cq_event(rxq->cq->channel, &ev_cq,
> &ev_ctx);
> - if (ret || ev_cq != rxq->cq)
> + /** For non-zero ret save the errno (may be EAGAIN
> + * which means the get_cq_event function was called before
> + * receiving one).
> + */
> + if (ret)
> + ret = errno;
> + else if (ev_cq != rxq->cq)
> ret = EINVAL;
> }
> if (ret) {
> rte_errno = ret;
> - WARN("unable to disable interrupt on rx queue %d",
> - idx);
> + if (ret != EAGAIN)
> + WARN("unable to disable interrupt on rx queue %d",
> + idx);
> } else {
> rxq->mcq.arm_sn++;
> mlx4_glue->ack_cq_events(rxq->cq, 1);
> --
> 2.8.4
Patch applied to next-net-mlx,
Kindest regards,
Raslan Darawsheh
@@ -326,13 +326,20 @@ mlx4_rx_intr_disable(struct rte_eth_dev *dev, uint16_t idx)
} else {
ret = mlx4_glue->get_cq_event(rxq->cq->channel, &ev_cq,
&ev_ctx);
- if (ret || ev_cq != rxq->cq)
+ /** For non-zero ret save the errno (may be EAGAIN
+ * which means the get_cq_event function was called before
+ * receiving one).
+ */
+ if (ret)
+ ret = errno;
+ else if (ev_cq != rxq->cq)
ret = EINVAL;
}
if (ret) {
rte_errno = ret;
- WARN("unable to disable interrupt on rx queue %d",
- idx);
+ if (ret != EAGAIN)
+ WARN("unable to disable interrupt on rx queue %d",
+ idx);
} else {
rxq->mcq.arm_sn++;
mlx4_glue->ack_cq_events(rxq->cq, 1);