incubator-nuttx

History

zhanghongyu db4840564d dns: Reduce the dns_lock granularity When a7 curl calls dns_query via usrsock, it will wait a usrsock response with the dns lock held. If a7 rptun recv a dns_addnameserver event from another core at this time, rptun waits the lock held by curl in callback. Then curl will never get its usrsock response with rptun blocked, so the deadlock occurs. This change will break lock when do usrsock request. Signed-off-by: zhanghongyu <zhanghongyu@xiaomi.com>		2022-11-11 20:07:05 +08:00
..
libc	dns: Reduce the dns_lock granularity	2022-11-11 20:07:05 +08:00
libdsp	Fix various typos	2022-07-08 02:15:54 +08:00
libnx	tools: replace INCDIR to Makefile variable	2022-11-03 19:59:55 +08:00
libxx	tools: replace DEFINE script to Makefile variable	2022-11-03 19:59:55 +08:00
README.txt	…

README.txt

README
======

This directory holds NuttX libraries.  Libraries in NuttX are very special
creatures.  They have these properties:

1. They can be shared by both application logic and logic within the OS when
   using the FLAT build.

2. But in PROTECTED and KERNEL modes, they must be built differently:  The
   copies used by applications and the OS cannot be the same.  Rather,
   separate versions of libraries must be built for the kernel and for
   applications.

3. When used by the OS, some special care must be taken to assure that the
   OS logic does not disrupt the user's errno value and that the OS does
   not create inappropriate cancellation points.

   For example, sem_wait() is both a cancellation point and modifies the
   errno value.  So within the FLAT build and without kernel version for
   the PROTECTED and KERNEL builds, the special internal OS interface
   nxsem_wait() must be used.  Within libraries, the macro _SEM_WAIT()
   (as defined in include/nuttx/semaphore.h) is used instead.  The
   definition of this macro accounts for the different usage environments.

NOTE:  The libraries under libs/ build differently from other NuttX
components:  There are no build-related files in the libs/ directory; it
is simply a container for other well-known, individual library directories.
The upper level Makefile logic is aware of the libraries within the libs/
container.

The only real function of the libs/ directory is to prevent the top-level
directory from becoming cluttered with individual libraries.