examples:
There are two threads involved: thread A with a priority of 100 and
thread B with a priority of 101. Here's how they interact:
When thread A releases a semaphore, thread B is scheduled to execute
some code and may reacquire the semaphore. If no other tasks are ready,
thread A will be scheduled to run.
This continuous process can lead to a busy loop.
Thread A: Thread B:
while (nxsem_get_value(&priv->wait, &semcount) >= 0 && <---
semcount <= 0) | 2)context switch
{ 1)contex switch |
nxsem_post(&priv->wait); -------------> run some code and nxsem_wait again
}
Signed-off-by: dongjiuzhu1 <dongjiuzhu1@xiaomi.com>
Most tools used for compliance and SBOM generation use SPDX identifiers
This change brings us a step closer to an easy SBOM generation.
Signed-off-by: Alin Jerpelea <alin.jerpelea@sony.com>
currently, nuttx implements readv/writev on the top of read/write.
while it might work for the simplest cases, it's broken by design.
for example, it's impossible to make it work correctly for files
which need to preserve data boundaries without allocating a single
contiguous buffer. (udp socket, some character devices, etc)
this change is a start of the migration to a better design.
that is, implement read/write on the top of readv/writev.
to avoid a single huge change, following things will NOT be done in
this commit:
* fix actual bugs caused by the original readv-based-on-read design.
(cf. https://github.com/apache/nuttx/pull/12674)
* adapt filesystems/drivers to actually benefit from the new interface.
(except a few trivial examples)
* eventually retire the old interface.
* retire read/write syscalls. implement them in libc instead.
* pread/pwrite/preadv/pwritev (except the introduction of struct uio,
which is a preparation to back these variations with the new
interface.)
