Re: [dpdk-dev] [PATCH] mbuf: allow dynamic flags to be used by secondary process

[Olivier Matz <olivier.matz@6wind.com>]

Hi Stephen,

On Thu, Oct 15, 2020 at 10:20:19AM -0700, Stephen Hemminger wrote:
> mbuf: allow dynamic flags to be used by secondary process

Suggested title:
mbuf: fix dynamic flags lookup from secondary process

>
> The dynamic flag management is broken for multi-process environment.
> All calls to lookup dynamic flags or fields will fail in secondary process.
> This is because the local pointer to the memzone is not ever initialized.
> 
> Fix it by using the same checks as dynfield_register().
> I.e if shared memory zone has not been looked up already,
> then discover it.
> 
> Fixes: 4958ca3a443a ("mbuf: support dynamic fields and flags")
> Cc: olivier.matz@6wind.com
> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>

Good catch, please Cc stable for v2.

> ---
>  lib/librte_mbuf/rte_mbuf_dyn.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/librte_mbuf/rte_mbuf_dyn.c b/lib/librte_mbuf/rte_mbuf_dyn.c
> index 538a43f6959f..ac4801b4d770 100644
> --- a/lib/librte_mbuf/rte_mbuf_dyn.c
> +++ b/lib/librte_mbuf/rte_mbuf_dyn.c
> @@ -185,7 +185,7 @@ rte_mbuf_dynfield_lookup(const char *name, struct rte_mbuf_dynfield *params)
>  {
>  	struct mbuf_dynfield_elt *mbuf_dynfield;
>  
> -	if (shm == NULL) {
> +	if (shm == NULL && init_shared_mem() < 0) {
>  		rte_errno = ENOENT;
>  		return -1;
>  	}

init_shared_mem() is supposed to be called with tailq lock held.

I think the test (shm == NULL && init_shared_mem() < 0) should be
moved in __mbuf_dynfield_lookup().

> @@ -384,7 +384,7 @@ rte_mbuf_dynflag_lookup(const char *name,
>  {
>  	struct mbuf_dynflag_elt *mbuf_dynflag;
>  
> -	if (shm == NULL) {
> +	if (shm == NULL && init_shared_mem() < 0) {
>  		rte_errno = ENOENT;
>  		return -1;
>  	}

Same here


Thanks,
Olivier