[dpdk-dev] eal: can not run secondary process on openstack environment

[陈亚辉-云杉研发部]

Deleting xdg_runtime_dir and fallback, runtime_dir will always be
"/var/run" defined by code:
static const char *default_runtime_dir = "/var/run"

Here is my patch:
# diff -ruN  ~/dpdk-18.11.6/lib/librte_eal/linuxapp/eal/eal_orig.c eal.c
--- ~/dpdk-18.11.6/lib/librte_eal/linuxapp/eal/eal_orig.c        2020-04-14
12:16:04.774609296 +0800
+++ eal.c       2020-04-30 11:29:26.526918889 +0800
@@ -105,18 +105,9 @@
 eal_create_runtime_dir(void)
 {
        const char *directory = default_runtime_dir;
-       const char *xdg_runtime_dir = getenv("XDG_RUNTIME_DIR");
-       const char *fallback = "/tmp";
        char tmp[PATH_MAX];
        int ret;

-       if (getuid() != 0) {
-               /* try XDG path first, fall back to /tmp */
-               if (xdg_runtime_dir != NULL)
-                       directory = xdg_runtime_dir;
-               else
-                       directory = fallback;
-       }
        /* create DPDK subdirectory under runtime dir */
        ret = snprintf(tmp, sizeof(tmp), "%s/dpdk", directory);
        if (ret < 0 || ret == sizeof(tmp)) {

Date: Fri, 17 Apr 2020 14:52:58 +0100
From: "Burakov, Anatoly" <anatoly.burakov at intel.com>
To: ???-?????  <goodluckwillcomesoon at gmail.com>, dev at dpdk.org,
        jiping at yunshan.net, xiangyang at yunshan.net
Subject: Re: [dpdk-dev] eal: can not run secondary process on
        openstack environment
Message-ID: <8f5bb1c4-7572-0c18-ecab-89c1340430cb at intel.com>
Content-Type: text/plain; charset=utf-8; format=flowed

On 15-Apr-20 11:06 AM, ???-????? wrote:
> dpdk version: 18.11
>
> Ovs-dpdk runs as openvswitch account on the openstack environment. Use the
> root account to run another --proc-type=secondary program,
> such as dpdk-pdump or helloword with parameter --proc-type=secondary , and
> it will report an Err: Cannot open '/var/run/dpdk/rte/config' for
> rte_mem_config.
>
> Check the source code eal.c:
>
> int
> eal_create_runtime_dir(void)
> {
>          const char *directory = default_runtime_dir;
>          const char *xdg_runtime_dir = getenv("XDG_RUNTIME_DIR");
>          const char *fallback = "/tmp";
>          char tmp[PATH_MAX];
>          int ret;
>
>          if (getuid() != 0) {
>                  /* try XDG path first, fall back to /tmp */
>                  if (xdg_runtime_dir != NULL)
>                          directory = xdg_runtime_dir;
>                  else
>                          directory = fallback;
>          }
>
>          /* create DPDK subdirectory under runtime dir */
>          ret = snprintf(tmp, sizeof(tmp), "%s/dpdk", directory);
>          if (ret < 0 || ret == sizeof(tmp)) {
>                  RTE_LOG(ERR, EAL, "Error creating DPDK runtime path
> name\n");
>                  return -1;
>          }
>
>          /* create prefix-specific subdirectory under DPDK runtime dir */
>          ret = snprintf(runtime_dir, sizeof(runtime_dir), "%s/%s",
>                          tmp, eal_get_hugefile_prefix());
>          if (ret < 0 || ret == sizeof(runtime_dir)) {
>                  RTE_LOG(ERR, EAL, "Error creating prefix-specific runtime
> path name\n");
>                  return -1;
>          }
>
> The root account is corresponds to the directory /var/run/DPDK/rte, but
> openvswitch account is directory /var/run/openvswitch DPDK/rte.
> Then, I changed to the openvswitch account and run the process again,
> errors below were reported:
>      EAL: Detected 40 lcore(s)
>      EAL: Detected 2 NUMA nodes
>      EAL: Multi-process socket
> /var/run/openvswitch/dpdk/rte/mp_socket_306857_7e76690dafe702
>      EAL: Probing VFIO support...
>      EAL: VFIO support initialized
>      EAL: Could not map memory from primary process
>      EAL: FATAL: Cannot init memory
>      EAL: Cannot init memory
>
> There seems to be insufficient permissions. So, I change the code blow and
> all the things get to be OK:
>
> int
> eal_create_runtime_dir(void)
> {
>          const char *directory = default_runtime_dir;
>          const char *xdg_runtime_dir = getenv("XDG_RUNTIME_DIR");
>          const char *fallback = "/tmp";
>          char tmp[PATH_MAX];
>          int ret;
>
>          if (getuid() != 0) {
>                  /* try XDG path first, fall back to /tmp */
>                  if (xdg_runtime_dir != NULL)
>                          directory = xdg_runtime_dir;
>                  else
>                          directory = fallback;
>          }
>
>          directory = "/var/run/openvswitch"; // added by my for
test.........
>          /* create DPDK subdirectory under runtime dir */
>          ret = snprintf(tmp, sizeof(tmp), "%s/dpdk", directory);
>          if (ret < 0 || ret == sizeof(tmp)) {
>                  RTE_LOG(ERR, EAL, "Error creating DPDK runtime path
> name\n");
>                  return -1;
>          }
>
> This is supposed to be a DPDK BUG. Considering that the primary and
> secondary processes may not be the same account,
> process with parameter --proc-type=secondary should get the runtime
> directory from the primary process instead of
> generating a directory as it does now.
>

I'm not sure how would that even be accomplished, because there is no
way the initializing secondary process knows where to look for primary
processes. Do you have any suggestions as to the mechanism of finding a
primary process in such case?

--
Thanks,
Anatoly