Nuttx currently has 2 types of sleep interfaces: 1. Signal-scheduled sleep: nxsig_sleep() / nxsig_usleep() / nxsig_nanosleep() Weaknesses: a. Signal-dependent: The signal-scheduled sleep method is bound to the signal framework, while some driver sleep operations do not depend on signals. b. Timespec conversion: Signal-scheduled sleep involves timespec conversion, which has a significant impact on performance. 2. Busy sleep: up_mdelay() / up_udelay() Weaknesses: a. Does not actively trigger scheduling, occupy the CPU loading. 3. New interfaces: Scheduled sleep: nxsched_sleep() / nxsched_usleep() / nxsched_msleep() / nxsched_ticksleep() Strengths: a. Does not depend on the signal framework. b. Tick-based, without additional computational overhead. Currently, the Nuttx driver framework extensively uses nxsig_* interfaces. However, the driver does not need to rely on signals or timespec conversion. Therefore, a new set of APIs is added to reduce dependencies on other modules. (This PR also aims to make signals optional, further reducing the code size of Nuttx.) Signed-off-by: chao an <anchao.archer@bytedance.com>
Apache NuttX is a real-time operating system (RTOS) with an emphasis on standards compliance and small footprint. Scalable from 8-bit to 64-bit microcontroller environments, the primary governing standards in NuttX are POSIX and ANSI standards. Additional standard APIs from Unix and other common RTOSs (such as VxWorks) are adopted for functionality not available under these standards, or for functionality that is not appropriate for deeply-embedded environments (such as fork()).
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