[dpdk-stable] [EXT] [PATCH v3] examples/eventdev: refactor ethdev port stop

[Pavan Nikhilesh Bhagavatula]

Hi Feifei,

>Move eth stop code from "signal_handler" function to the end of
>"main"
>function. There are two reasons for this:
>
>First, this improves code maintenance and makes code look simple and
>clear. Based on this change, after receiving the interrupt signal,
>"fdata->done" is set as 1. Then the main thread will wait all worker
>lcores to jump out of the loop. Finally, the main thread will stop and
>then close eth dev port.
>
>Second, for older version, the main thread first stops eth dev port and
>then waits the end of worker lcore. This may cause errors because it
>may
>stop the eth dev port which worker lcores are using. This moving
>change
>can fix this by waiting all worker threads to exit and then stop the
>eth dev port.

Apologies for the delayed reply,

In case of event dev the workers don't interact with eth device directly, 
Instead eth device "injects" packets into event device and event device
is responsible for scheduling them to the workers.

If the producer is not stopped i.e. in this case eth device then the worker
threads might never exit and the main core would wait indefinitely for
workers to exit. This will be predominantly seen in cases where there are
only a few flows and large number of workers causing a lot of intra thread
dependency.

Regards,
Pavan.

>
>In the meanwhile, remove wmb in signal_handler.
>
>This is because when the main lcore receive the stop signal, it stores 1
>into fdata->done. And then the worker lcores load "fdata->done" and
>jump
>out of the loop to stop running. Nothing should be stored after
>updating
>fdata->done, so the wmb is unnecessary.
>
>Fixes: 085edac2ca38 ("examples/eventdev_pipeline: support Tx
>adapter")
>Cc: pbhagavatula at marvell.com
>Cc: stable at dpdk.org
>
>Suggested-by: Ruifeng Wang <ruifeng.wang at arm.com>
>Signed-off-by: Feifei Wang <feifei.wang2 at arm.com>
>Reviewed-by: Ruifeng Wang <ruifeng.wang at arm.com>
>Reviewed-by: Honnappa Nagarahalli
><honnappa.nagarahalli at arm.com>
>Acked-by: Harry van Haaren <harry.van.haaren at intel.com>
>---
>
>v2:
>1. Delete unused variable to fix build error
>2. Reduce commit message length to fix coding style issues
>
>v3:
>1. Title improvement (Van Haaren)
>
> examples/eventdev_pipeline/main.c | 16 ++++------------
> 1 file changed, 4 insertions(+), 12 deletions(-)
>
>diff --git a/examples/eventdev_pipeline/main.c
>b/examples/eventdev_pipeline/main.c
>index 823f8b51c..fdbaf667b 100644
>--- a/examples/eventdev_pipeline/main.c
>+++ b/examples/eventdev_pipeline/main.c
>@@ -280,7 +280,6 @@ static void
> signal_handler(int signum)
> {
> 	static uint8_t once;
>-	uint16_t portid;
>
> 	if (fdata->done)
> 		rte_exit(1, "Exiting on signal %d\n", signum);
>@@ -291,17 +290,6 @@ signal_handler(int signum)
> 			rte_event_dev_dump(0, stdout);
> 		once = 1;
> 		fdata->done = 1;
>-		rte_smp_wmb();
>-
>-		RTE_ETH_FOREACH_DEV(portid) {
>-			rte_event_eth_rx_adapter_stop(portid);
>-			rte_event_eth_tx_adapter_stop(portid);
>-			if (rte_eth_dev_stop(portid) < 0)
>-				printf("Failed to stop port %u", portid);
>-		}
>-
>-		rte_eal_mp_wait_lcore();
>-
> 	}
> 	if (signum == SIGTSTP)
> 		rte_event_dev_dump(0, stdout);
>@@ -465,6 +453,10 @@ main(int argc, char **argv)
> 	}
>
> 	RTE_ETH_FOREACH_DEV(portid) {
>+		rte_event_eth_rx_adapter_stop(portid);
>+		rte_event_eth_tx_adapter_stop(portid);
>+		if (rte_eth_dev_stop(portid) < 0)
>+			printf("Failed to stop port %u", portid);
> 		rte_eth_dev_close(portid);
> 	}
>
>--
>2.25.1