[dpdk-dev] [PATCH] net/failsafe: fix Rx clean race

[Matan Azrad]

In case of plug out, the RMV interrupt callback sets the remove flag of
the removed sub-device. The next hotplug alarm cycle should read this
flag and if the data path are clean it should remove the sub-device.

In case of fail-safe RX burst calling from application, fail-afe tries
to call to all STARTED sub-device rx_burst functions. The remove flag
is not checked here and fail-safe may call to the removed sub-device
rx_burst function.

The above 2 cases run in different threads and there is a race between
the removed sub-device RX clean check to the removed sub-device
rx_burst call makes the sub device RX unclean.

If the application calls to rx_burst in loop, the probability to get RX
clean is not enough, especially when there are few sub-devices or if the
rx_burst function of the removed sub-device takes a lot of time.

Each time the sub-device data path is unclean, the second oportunity to
check it again should be only in the hotplug alarm next cycle; the
default time between cycles is 2 seconds.

In this loop when fail-safe tries to remove the sub-device, the
sub-device may appear back and fail-safe cannot plug it in back until
the removal process is completted. In this time fail-safe may lose the
primary sub-device services and may hurt application performance.

This patch adds a remove flag check in safe rx_burst function.
By this way, at most one more hotplug alarm cycle is necessary
to get the sub-device clean for actual removal.

Fixes: 72a57bfd9a0e ("net/failsafe: add fast burst functions")
Cc: stable at dpdk.org

Signed-off-by: Matan Azrad <matan at mellanox.com>
---
 drivers/net/failsafe/failsafe_rxtx.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/failsafe/failsafe_rxtx.c b/drivers/net/failsafe/failsafe_rxtx.c
index 7311421..70157c8 100644
--- a/drivers/net/failsafe/failsafe_rxtx.c
+++ b/drivers/net/failsafe/failsafe_rxtx.c
@@ -43,7 +43,8 @@
 {
 	return (ETH(sdev) == NULL) ||
 		(ETH(sdev)->rx_pkt_burst == NULL) ||
-		(sdev->state != DEV_STARTED);
+		(sdev->state != DEV_STARTED) ||
+		(sdev->remove != 0);
 }
 
 static inline int
-- 
1.8.3.1