Re: [dpdk-dev] [PATCH] telemetry: remove internal symbol from public header

[Jerin Jacob <jerinjacobk@gmail.com>]

On Wed, May 5, 2021 at 2:14 PM David Marchand <david.marchand@redhat.com> wrote:
>
> On Tue, May 4, 2021 at 6:19 PM Power, Ciara <ciara.power@intel.com> wrote:
> >
> > >-----Original Message-----
> > >From: Richardson, Bruce <bruce.richardson@intel.com>
> > >Sent: Tuesday 4 May 2021 13:14
> > >To: jerinj@marvell.com
> > >Cc: Power, Ciara <ciara.power@intel.com>; dev@dpdk.org;
> > >thomas@monjalon.net
> > >Subject: Re: [PATCH] telemetry: remove internal symbol from public header
> > >
> > >On Mon, May 03, 2021 at 10:04:28PM +0530, jerinj@marvell.com wrote:
> > >> From: Jerin Jacob <jerinj@marvell.com>
> > >>
> > >> Remove TELEMETRY_MAX_CALLBACKS symbol from public rte_telemetry.h
> > >> header file.
> > >>
> > >> Signed-off-by: Jerin Jacob <jerinj@marvell.com>
> > >> ---
> > >Acked-by: Bruce Richardson <bruce.richardson@intel.com>
> >
> > Thanks,
> > Acked-by: Ciara Power <ciara.power@intel.com>
>
> I agree this define should be hidden.
>
> Just, what do you think of using a dynamic allocation and remove the
> limitation entirely?

I think, that may be better. Probably this patch can go in rc2.

The dynamic feature can be pushed to the next release.

I will leave it to the maintainers to decide. I am fine with any scheme.

>
>
> diff --git a/lib/telemetry/rte_telemetry.h b/lib/telemetry/rte_telemetry.h
> index 031db9e968..8776998b54 100644
> --- a/lib/telemetry/rte_telemetry.h
> +++ b/lib/telemetry/rte_telemetry.h
> @@ -10,8 +10,6 @@
>  #ifndef _RTE_TELEMETRY_H_
>  #define _RTE_TELEMETRY_H_
>
> -/** Maximum number of telemetry callbacks. */
> -#define TELEMETRY_MAX_CALLBACKS 64
>  /** Maximum length for string used in object. */
>  #define RTE_TEL_MAX_STRING_LEN 64
>  /** Maximum length of string. */
> @@ -285,7 +283,7 @@ typedef void * (*handler)(void *sock_id);
>   * @return
>   *  -EINVAL for invalid parameters failure.
>   *  @return
> - *  -ENOENT if max callbacks limit has been reached.
> + *  -ENOMEM for mem allocation failure.
>   */
>  __rte_experimental
>  int
> diff --git a/lib/telemetry/telemetry.c b/lib/telemetry/telemetry.c
> index 68b479e0e4..6baba57ec2 100644
> --- a/lib/telemetry/telemetry.c
> +++ b/lib/telemetry/telemetry.c
> @@ -59,7 +59,7 @@ static uint32_t logtype;
>          rte_log_ptr(RTE_LOG_ ## l, logtype, "TELEMETRY: " __VA_ARGS__)
>
>  /* list of command callbacks, with one command registered by default */
> -static struct cmd_callback callbacks[TELEMETRY_MAX_CALLBACKS];
> +static struct cmd_callback *callbacks;
>  static int num_callbacks; /* How many commands are registered */
>  /* Used when accessing or modifying list of command callbacks */
>  static rte_spinlock_t callback_sl = RTE_SPINLOCK_INITIALIZER;
> @@ -70,15 +70,21 @@ static uint16_t v2_clients;
>  int
>  rte_telemetry_register_cmd(const char *cmd, telemetry_cb fn, const char *help)
>  {
> +       struct cmd_callback *new_callbacks;
>         int i = 0;
>
>         if (strlen(cmd) >= MAX_CMD_LEN || fn == NULL || cmd[0] != '/'
>                         || strlen(help) >= MAX_HELP_LEN)
>                 return -EINVAL;
> -       if (num_callbacks >= TELEMETRY_MAX_CALLBACKS)
> -               return -ENOENT;
>
>         rte_spinlock_lock(&callback_sl);
> +       new_callbacks = realloc(callbacks, sizeof(callbacks[0]) *
> (num_callbacks + 1));
> +       if (new_callbacks == NULL) {
> +               rte_spinlock_unlock(&callback_sl);
> +               return -ENOMEM;
> +       }
> +       callbacks = new_callbacks;
> +
>         while (i < num_callbacks && strcmp(cmd, callbacks[i].cmd) > 0)
>                 i++;
>         if (i != num_callbacks)
>
>
> And there is a race to fix in list_commands() (which accesses the
> callbacks array without taking the lock).
>
> --
> David Marchand
>