On 4/26/2023 4:10 AM, Ville JUven wrote:
I know it might be too late to fix the usage of SEM_INITIALIZER macro
from user space, as many out-of-tree targets might depend on this as
well, but I'd still like to open a discussion about the possibility of
removing it from user space.
Why remove it? SEM_INITIALIZER is a non-standard way of initializing
the semaphore structure. This is only possible because the full
composition of sem_t is visible to the user, including all of the
kernel private data (waitlist, priority inheritance info). If the
composition is hidden / moved (IMO the user should _not_ know the
implementation defined composition of sem_t) , then the initializer
list will become unfeasible.
SEM_INITIALIZER was added many years ago when NuttX was a tiny OS that
was just /mostly POSIX/. Now the OS has grown and matured and stricter
POSIX-like behavior is more mission critical. So I would be supportive
of removing it because it is a tiny step toward POSIX compliance.
However, you will probably have to deal with the reason why
SEM_INITIALIZER was created in the first place: There are many places
where semaphores are declared and sem_init() cannot be called to
initialize them. For example, when the sem_t is defined but there is no
initialization function that runs to call sem_init() or when the sem_t
is member of a more complex type like an array of structures with unions.
I am not sure if there are any cases like this in user-space, but if so
those cases will require some re-design.
