On Fri, Sep 12, 2025 at 8:27 AM Khadem Ullah <14pwcse1224@uetpeshawar.edu.pk>
wrote:

> Hi Stephen,
>
> On Fri, Sep 12, 2025, 04:51 Stephen Hemminger <stephen@networkplumber.org>
> wrote:
>
>>
>> Ok, the Windows #ifdef was confusing me then looked more closely.
>> This patch is adding a set of rings so that primary and secondary
>> can communicate, the adding one command.
>>
>> The idea is good, but there is a better way to handle this.
>> There already exists a way for primary and secondary to communicate
>> through the mp service. This is used for hotplug and pdump and probably
>> other things as well.
>>
> Yeah, agree. Testpmd have also hutplug callbacks, I have tried that too,
> but it is in lower layer to call any stopping fwd_engines.
>
>>
>> The communication can be either way, for example I proposed patches
>> to pdump so that primary can tell secondary to participate.
>>
>>
>> https://patchwork.dpdk.org/project/dpdk/patch/20250814165307.12786-7-stephen@networkplumber.org/
>>
>> This of testpmd can be done in similar way.
>> The handler in secondary should be able to act same as
>> when SIGINT is received. Set the flag f_exit which will cause the main
>> loop to exit.
>>
>> This can then happen immediately, and the proc monitor alarm function
>> is only then needed to handle when primary process crashes.
>>
> Yeah, we can try that, my only concern is that if it can handle and stop
> any numbers of secondary processes fwd_engines as the current solution can
> stop.
>
> Please check the __handle_primary_request in
https://elixir.bootlin.com/dpdk/v25.07/source/lib/eal/common/hotplug_mp.c#L225
,
testpmd is calling this api during hutplug callbacks.
I had tried a similar one as proposed in pdump but could not call
stop_packet_forwarding from this lower layer as given below.
There is only eal_bus_cleanup(), and local_dev_remove support. We only left
with the ring solution
to used if for IPC as in
https://elixir.bootlin.com/dpdk/v25.07/source/examples/multi_process/simple_mp/main.c#L75


git diff
diff --git a/app/test-pmd/testpmd.c b/app/test-pmd/testpmd.c
index 0f58a31eb5..9155453efa 100644
--- a/app/test-pmd/testpmd.c
+++ b/app/test-pmd/testpmd.c
@@ -72,6 +72,7 @@
 #endif
 #ifdef RTE_NET_MLX5
 #include "mlx5_testpmd.h"
+#include "hotplug_mp.h"
 #endif

 #include "testpmd.h"
@@ -3634,6 +3635,11 @@ pmd_test_exit(void)
                        printf("\nStopping port %d...\n", pt_id);
                        fflush(stdout);
                        stop_port(pt_id);
+                       printf("Stopping secondary process...\n");
+                       struct eal_dev_mp_req req;
+                       memset(&req, 0, sizeof(req));
+                       req.t = ETH_REQ_STOP; //EAL_DEV_REQ_TYPE_DETACH;
+                       eal_dev_hotplug_request_to_secondary(&req);
                }
                RTE_ETH_FOREACH_DEV(pt_id) {
                        printf("\nShutting down port %d...\n", pt_id);
diff --git a/lib/eal/common/hotplug_mp.c b/lib/eal/common/hotplug_mp.c
index 17089ca3db..d324db428f 100644
--- a/lib/eal/common/hotplug_mp.c
+++ b/lib/eal/common/hotplug_mp.c
@@ -239,6 +239,11 @@ static void __handle_primary_request(void *param)
        memset(&mp_resp, 0, sizeof(mp_resp));

        switch (req->t) {
+       case ETH_REQ_STOP:
+               printf("__handle_secondary_request called "
+                       "for secondary processes fwd_engine stopping...\n");
+               //eal_bus_cleanup();
+               break;
        case EAL_DEV_REQ_TYPE_ATTACH:
        case EAL_DEV_REQ_TYPE_DETACH_ROLLBACK:
                ret = local_dev_probe(req->devargs, &dev);
diff --git a/lib/eal/common/hotplug_mp.h b/lib/eal/common/hotplug_mp.h
index 7221284286..7a46285994 100644
--- a/lib/eal/common/hotplug_mp.h
+++ b/lib/eal/common/hotplug_mp.h
@@ -19,6 +19,7 @@ enum eal_dev_req_type {
        EAL_DEV_REQ_TYPE_DETACH,
        EAL_DEV_REQ_TYPE_ATTACH_ROLLBACK,
        EAL_DEV_REQ_TYPE_DETACH_ROLLBACK,
+       ETH_REQ_STOP,
 };