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4d39d6e2f3
The mutex used to sync the reader and writer of the pipe is initialized as unlocked. This results in a bit of wasted CPU cycles the first time a read blocks. This patch inits the mutex in a locked state so that the first blocking read blocks immediately.
58 lines
1.2 KiB
C
58 lines
1.2 KiB
C
/*
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* Copyright (C) 2016 Kaspar Schleiser <kaspar@schleiser.de>
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*
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* This file is subject to the terms and conditions of the GNU Lesser
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* General Public License v2.1. See the file LICENSE in the top level
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* directory for more details.
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*/
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/**
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* @ingroup sys
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* @{
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* @file
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* @brief ISR -> userspace pipe implementation
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*
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* @author Kaspar Schleiser <kaspar@schleiser.de>
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*
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* @}
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*/
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#include "isrpipe.h"
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void isrpipe_init(isrpipe_t *isrpipe, uint8_t *buf, size_t bufsize)
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{
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isrpipe->mutex = (mutex_t)MUTEX_INIT_LOCKED;
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tsrb_init(&isrpipe->tsrb, buf, bufsize);
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}
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int isrpipe_write_one(isrpipe_t *isrpipe, uint8_t c)
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{
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int res = tsrb_add_one(&isrpipe->tsrb, c);
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/* `res` is either 0 on success or -1 when the buffer is full. Either way,
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* unlocking the mutex is fine.
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*/
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mutex_unlock(&isrpipe->mutex);
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return res;
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}
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int isrpipe_write(isrpipe_t *isrpipe, const uint8_t *buf, size_t n)
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{
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int res = tsrb_add(&isrpipe->tsrb, buf, n);
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mutex_unlock(&isrpipe->mutex);
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return res;
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}
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int isrpipe_read(isrpipe_t *isrpipe, uint8_t *buffer, size_t count)
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{
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int res;
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while (!(res = tsrb_get(&isrpipe->tsrb, buffer, count))) {
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mutex_lock(&isrpipe->mutex);
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}
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return res;
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}
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