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fix(newlib): usleep returning early

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This commit updates usleep() to always sleep for the required sleep
period or more. This fixes a bug where the usleep() could sleep for less
than the request sleep period.

Closes https://github.com/espressif/esp-idf/pull/15132
This commit is contained in:
Stephen Noonan
2025-01-03 16:47:19 -05:00
committed by Sudeep Mohanty
parent 21a3ace68d
commit b47f25ac23
1 changed files with 21 additions and 5 deletions
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26
components/newlib/time.c
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@ -1,5 +1,5 @@
/*
* SPDX-FileCopyrightText: 2015-2022 Espressif Systems (Shanghai) CO LTD
* SPDX-FileCopyrightText: 2015-2025 Espressif Systems (Shanghai) CO LTD
*
* SPDX-License-Identifier: Apache-2.0
*/
@ -201,10 +201,26 @@ int usleep(useconds_t us)
if (us < us_per_tick) {
esp_rom_delay_us((uint32_t) us);
} else {
/* since vTaskDelay(1) blocks for anywhere between 0 and portTICK_PERIOD_MS,
* round up to compensate.
*/
vTaskDelay((us + us_per_tick - 1) / us_per_tick);
/* vTaskDelay may return up to (n-1) tick periods due to the tick ISR
being asynchronous to the call. We must sleep at least the specified
time, or longer. Checking the monotonic clock allows making an
additional call to vTaskDelay when needed to ensure minimal time is
actually slept. Adding `us_per_tick - 1` prevents ever passing 0 to
vTaskDelay().
*/
uint64_t now_us = esp_time_impl_get_time();
uint64_t target_us = now_us + us;
do {
vTaskDelay((((target_us - now_us) + us_per_tick - 1) / us_per_tick));
now_us = esp_time_impl_get_time();
/* It is possible that the time left until the target time is less
* than a tick period. However, we let usleep() to sleep for an
* entire tick period. This, could result in usleep() sleeping for
* a longer time than the requested time but that does not violate
* the spec of usleep(). Additionally, it allows FreeRTOS to schedule
* other tasks while the current task is sleeping.
*/
} while (now_us < target_us);
}
return 0;
}