Re: [dpdk-stable] [PATCH 19.11.9 2/2] eal: fix hang in control thread creation

[Christian Ehrhardt <christian.ehrhardt@canonical.com>]

On Fri, May 21, 2021 at 5:49 PM Luc Pelletier <lucp.at.work@gmail.com> wrote:
>
> [ upstream commit af68c1d699be6c369e296b775bdbf13ae18b79cc ]
>
> The affinity of a control thread is set after it has been launched. If
> setting the affinity fails, pthread_cancel is called followed by a call
> to pthread_join, which can hang forever if the thread's start routine
> doesn't call a pthread cancellation point.
>
> This patch modifies the logic so that the control thread exits
> gracefully if the affinity cannot be set successfully and removes the
> call to pthread_cancel.
>
> Fixes: 6383d2642b62 ("eal: set name when creating a control thread")
> ---

Thank you, applied to 19.11.9 (to become -rc2) now

>  lib/librte_eal/common/eal_common_thread.c | 29 +++++++++++++----------
>  1 file changed, 17 insertions(+), 12 deletions(-)
>
> diff --git a/lib/librte_eal/common/eal_common_thread.c b/lib/librte_eal/common/eal_common_thread.c
> index a5089ae49..b1e5c2a08 100644
> --- a/lib/librte_eal/common/eal_common_thread.c
> +++ b/lib/librte_eal/common/eal_common_thread.c
> @@ -161,12 +161,16 @@ static void ctrl_params_free(struct rte_thread_ctrl_params *params)
>  static void *rte_thread_init(void *arg)
>  {
>         struct rte_thread_ctrl_params *params = arg;
> -       void *(*start_routine)(void *) = params->start_routine;
> +       void *(*start_routine)(void *);
>         void *routine_arg = params->arg;
>
>         pthread_barrier_wait(&params->configured);
> +       start_routine = params->start_routine;
>         ctrl_params_free(params);
>
> +       if (start_routine == NULL)
> +               return NULL;
> +
>         return start_routine(routine_arg);
>  }
>
> @@ -188,14 +192,12 @@ rte_ctrl_thread_create(pthread_t *thread, const char *name,
>         params->refcnt = 2;
>
>         ret = pthread_barrier_init(&params->configured, NULL, 2);
> -       if (ret != 0) {
> -               free(params);
> -               return -ret;
> -       }
> +       if (ret != 0)
> +               goto fail_no_barrier;
>
>         ret = pthread_create(thread, attr, rte_thread_init, (void *)params);
>         if (ret != 0)
> -               goto fail;
> +               goto fail_with_barrier;
>
>         if (name != NULL) {
>                 ret = rte_thread_setname(*thread, name);
> @@ -206,19 +208,22 @@ rte_ctrl_thread_create(pthread_t *thread, const char *name,
>
>         ret = pthread_setaffinity_np(*thread, sizeof(*cpuset), cpuset);
>         if (ret != 0)
> -               goto fail_cancel;
> +               params->start_routine = NULL;
>
>         pthread_barrier_wait(&params->configured);
>         ctrl_params_free(params);
>
> -       return 0;
> +       if (ret != 0)
> +               /* start_routine has been set to NULL above; */
> +               /* ctrl thread will exit immediately */
> +               pthread_join(*thread, NULL);
>
> -fail_cancel:
> -       pthread_cancel(*thread);
> -       pthread_join(*thread, NULL);
> +       return -ret;
>
> -fail:
> +fail_with_barrier:
>         (void)pthread_barrier_destroy(&params->configured);
> +
> +fail_no_barrier:
>         free(params);
>
>         return -ret;
> --
> 2.25.1
>


-- 
Christian Ehrhardt
Staff Engineer, Ubuntu Server
Canonical Ltd