xiaoxiang781216 commented on a change in pull request #5498: URL: https://github.com/apache/incubator-nuttx/pull/5498#discussion_r810468502
########## 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: > Yes. I will examine the use case more carefully early next week. I briefly went thru lines now and I have a feeling that I solved a similar problem with `pthread_once` + `pthread_key_create` on the library init and then the created key was used to access allocated data (please see example from https://pubs.opengroup.org/onlinepubs/009695399/functions/pthread_key_create.html). I will try to understand what is the difference, but definitely need some more deep dive into what you are trying to solve. Your method can't handle multiple task case since pthread_key is specific to one task, in the new task you have to call pthread_key_create again. Basically, task local storage(attach pointer to each task) try to handle the similar problem as thread local storage(attach pointer to each thread in one task), but at the task level. It isn't a problem in the traditional POSIX OS(e.g. Linux, BSD, NuttX' Kernel mode), since they utilize MMU and each task/process has separate virtual address space, but it's an essential combability issue in NuttX's FLAT/PROTECTED mode. Apache NuttX Wiki has some article describe this problem: https://cwiki.apache.org/confluence/display/NUTTX/Linux+Processes+vs+NuttX+Tasks https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=152115079 -- 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
