[PATCH v5 2/6] eal: add thread lifetime management

[David Marchand]

Hello Tyler,

On Wed, Oct 5, 2022 at 7:07 PM Tyler Retzlaff
<roretzla at linux.microsoft.com> wrote:
> diff --git a/lib/eal/unix/rte_thread.c b/lib/eal/unix/rte_thread.c
> index 9126595..d4c1a7f 100644
> --- a/lib/eal/unix/rte_thread.c
> +++ b/lib/eal/unix/rte_thread.c
> @@ -16,6 +16,11 @@ struct eal_tls_key {
>         pthread_key_t thread_index;
>  };
>
> +struct thread_routine_ctx {
> +       rte_thread_func thread_func;
> +       void *routine_args;
> +};
> +
>  static int
>  thread_map_priority_to_os_value(enum rte_thread_priority eal_pri, int *os_pri,
>         int *pol)
> @@ -75,6 +80,136 @@ struct eal_tls_key {
>         return 0;
>  }
>
> +static void *
> +thread_func_wrapper(void *arg)
> +{
> +       struct thread_routine_ctx ctx = *(struct thread_routine_ctx *)arg;
> +
> +       free(arg);
> +
> +       return (void *)(uintptr_t)ctx.thread_func(ctx.routine_args);
> +}
> +
> +int
> +rte_thread_create(rte_thread_t *thread_id,
> +               const rte_thread_attr_t *thread_attr,
> +               rte_thread_func thread_func, void *args)
> +{
> +       int ret = 0;
> +       pthread_attr_t attr;
> +       pthread_attr_t *attrp = NULL;
> +       struct thread_routine_ctx *ctx;
> +       struct sched_param param = {
> +               .sched_priority = 0,
> +       };
> +       int policy = SCHED_OTHER;
> +
> +       ctx = calloc(1, sizeof(*ctx));
> +       if (ctx == NULL) {
> +               RTE_LOG(DEBUG, EAL, "Insufficient memory for thread context allocations\n");
> +               ret = ENOMEM;
> +               goto cleanup;
> +       }
> +       ctx->routine_args = args;
> +       ctx->thread_func = thread_func;
> +
> +       if (thread_attr != NULL) {
> +               ret = pthread_attr_init(&attr);
> +               if (ret != 0) {
> +                       RTE_LOG(DEBUG, EAL, "pthread_attr_init failed\n");
> +                       goto cleanup;
> +               }
> +
> +               attrp = &attr;
> +
> +               /*
> +                * Set the inherit scheduler parameter to explicit,
> +                * otherwise the priority attribute is ignored.
> +                */
> +               ret = pthread_attr_setinheritsched(attrp,
> +                               PTHREAD_EXPLICIT_SCHED);
> +               if (ret != 0) {
> +                       RTE_LOG(DEBUG, EAL, "pthread_attr_setinheritsched failed\n");
> +                       goto cleanup;
> +               }
> +
> +
> +               if (thread_attr->priority ==
> +                               RTE_THREAD_PRIORITY_REALTIME_CRITICAL) {
> +                       ret = ENOTSUP;
> +                       goto cleanup;
> +               }
> +               ret = thread_map_priority_to_os_value(thread_attr->priority,
> +                               &param.sched_priority, &policy);
> +               if (ret != 0)
> +                       goto cleanup;
> +
> +               ret = pthread_attr_setschedpolicy(attrp, policy);
> +               if (ret != 0) {
> +                       RTE_LOG(DEBUG, EAL, "pthread_attr_setschedpolicy failed\n");
> +                       goto cleanup;
> +               }
> +
> +               ret = pthread_attr_setschedparam(attrp, &param);
> +               if (ret != 0) {
> +                       RTE_LOG(DEBUG, EAL, "pthread_attr_setschedparam failed\n");
> +                       goto cleanup;
> +               }
> +       }
> +
> +       ret = pthread_create((pthread_t *)&thread_id->opaque_id, attrp,
> +               thread_func_wrapper, ctx);
> +       if (ret != 0) {
> +               RTE_LOG(DEBUG, EAL, "pthread_create failed\n");
> +               goto cleanup;
> +       }
> +
> +       if (thread_attr != NULL && CPU_COUNT(&thread_attr->cpuset) > 0) {
> +               ret = rte_thread_set_affinity_by_id(*thread_id,
> +                       &thread_attr->cpuset);
> +               if (ret != 0) {
> +                       RTE_LOG(DEBUG, EAL, "rte_thread_set_affinity_by_id failed\n");
> +                       goto cleanup;
> +               }
> +       }
> +
> +       ctx = NULL;
> +cleanup:
> +       free(ctx);
> +       if (attrp != NULL)
> +               pthread_attr_destroy(&attr);
> +
> +       return ret;
> +}

I am looking back at potential races in our code while reviewing the
ctrl thread creation fix, and I stopped at this patch.

What happens if rte_thread_set_affinity_by_id() fails?
A new thread got started, but I don't see it being terminated in the
cleanup phase.


In this same situation, we may have a small race for a double free on
ctx since thread_func_wrapper() may have already been called from the
new thread.


I have the same concerns with the windows implementation.


-- 
David Marchand