pussuw commented on PR #9716:
URL: https://github.com/apache/nuttx/pull/9716#issuecomment-1798075605
Hi @patacongo and @pkarashchenko
I'm currently working on a fix for semaphores in CONFIG_BUILD_KERNEL (all of
the sem_t data is in user memory) and I encountered this change.
Isn't the problem here simply the loop condition ?
```
ret = _SEM_ERRVAL(ret);
if (ret != -EINTR && ret != -ECANCELED)
{
break;
}
```
EINTR can be considered as "got woken by signal, try again", but ECANCELED
should break from the loop at once.
I also noticed a very old issue which duplicates this exact issue:
https://github.com/apache/nuttx/issues/619 and the fix was to break the
uninterruptible loop if ECANCELED is encountered.
So for some reason, the same error was duplicated into mutex.h / lib_mutex.c
later by:
https://github.com/apache/nuttx/commit/b88a8cf39ff1019ad787c4316b22ce29c7daa2dc
Isn't the fix just to remove ECANCELED from the ret != test and break the
loop if the calling thread is canceled ? Assuming ECANCELED will be handled
later (if we are indeed inside a nested cancellation point). This would remove
the need to add 1 extra system call to a direct kernel private procedure, which
would make the user API more coherent.
Why I bring this up is that exposing nx_semwait() to the userspace kind of
makes it impossible to know whether a semaphore request came from userspace or
from kernelspace.
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