xiaoxiang781216 commented on a change in pull request #5498: URL: https://github.com/apache/incubator-nuttx/pull/5498#discussion_r809779062
########## File path: sched/task/task_tls_alloc.c ########## @@ -0,0 +1,113 @@ +/**************************************************************************** + * sched/task/task_tls_alloc.c + * + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. The + * ASF licenses this file to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance with the + * License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT + * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the + * License for the specific language governing permissions and limitations + * under the License. + * + ****************************************************************************/ + +/**************************************************************************** + * Included Files + ****************************************************************************/ + +#include <sys/types.h> +#include <unistd.h> +#include <sched.h> +#include <errno.h> + +#include <nuttx/tls.h> +#include <nuttx/semaphore.h> + +/**************************************************************************** + * Private Data + ****************************************************************************/ + +#if CONFIG_TLS_TASK_NELEM > 0 + +static int g_tlsset = 0; +static sem_t g_tlssem = SEM_INITIALIZER(1); +static tls_dtor_t g_tlsdtor[CONFIG_TLS_TASK_NELEM]; + +/**************************************************************************** + * Public Functions + ****************************************************************************/ + +int task_tls_alloc(tls_dtor_t dtor) +{ + int ret; + int candidate; + + ret = nxsem_wait(&g_tlssem); + + if (ret < 0) + { + return ret; + } + + ret = -EAGAIN; + + for (candidate = 0; candidate < CONFIG_TLS_TASK_NELEM; candidate++) + { + int mask = 1 << candidate; + if ((g_tlsset & mask) == 0) + { + g_tlsset |= mask; + g_tlsdtor[candidate] = dtor; + ret = candidate; + break; + } + } + + nxsem_post(&g_tlssem); + return ret; +} + +/**************************************************************************** + * Name: task_tls_destruct + * + * Description: + * Destruct all TLS data element associated with allocated key + * + * Input Parameters: + * None + * + * Returned Value: + * A set of allocated TLS index + * + ****************************************************************************/ + +void task_tls_destruct(void) Review comment: > Why do we need `ta_telem[CONFIG_TLS_TASK_NELEM];` to be a member of `struct task_info_s`? I mean why it can't be global? and have only allocated index bits in `struct task_info_s` Because, each task need point to the different instance(please, consider my example, the library has the global variables, but want to support multiple clients at the same time): 1. All task(at the same index) use the same destructor to free the resource 2. Different task point to the different instance If you compare to TLS: 1. All thread in the same task share the same destruct callback 2. Different thread point to the different instance From the concept, task local storage is very similar to thread local storge, but at the task level. 1. Thread local storage allow the code allocate a task wide index with a destructor and attach a different pointer to the different thread at the same index in the same task. 2. Task local storage allow the code allocate a global index with a destructor and attach a different pointer to the different task at the same index. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: commits-unsubscr...@nuttx.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
