This commit backs out most of commit b4747286b1. That change was added because sem_wait() would sometimes cause cancellation points inappropriated. But with these recent changes, nxsem_wait() is used instead and it is not a cancellation point.
In the OS, all calls to sem_wait() changed to nxsem_wait(). nxsem_wait() does not return errors via errno so each place where nxsem_wait() is now called must not examine the errno variable.
In all OS functions (not libraries), change sem_wait() to nxsem_wait(). This will prevent the OS from creating bogus cancellation points and from modifying the per-task errno variable.
sched/semaphore: Add the function nxsem_wait(). This is a new internal OS interface. It is functionally equivalent to sem_wait() except that (1) it is not a cancellation point, and (2) it does not set the per-thread errno value on return.
sched/semaphore: Add nxsem_post() which is identical to sem_post() except that it never modifies the errno variable. Changed all references to sem_post in the OS to nxsem_post().
sched/semaphore: Add nxsem_destroy() which is identical to sem_destroy() except that it never modifies the errno variable. Changed all references to sem_destroy() in the OS to nxsem_destroy().
libc/semaphore and sched/semaphore: Add nxsem_getprotocol() and nxsem_setprotocola which are identical to sem_getprotocol() and set_setprotocol() except that they never modifies the errno variable. Changed all references to sem_setprotocol in the OS to nxsem_setprotocol(). sem_getprotocol() was not used in the OS
libc/semaphore: Add nxsem_getvalue() which is identical to sem_getvalue() except that it never modifies the errno variable. Changed all references to sem_getvalue in the OS to nxsem_getvalue().
sched/semaphore: Rename all internal private functions from sem_xyz to nxsem_xyz. The sem_ prefix is (will be) reserved only for the application semaphore interfaces.
libc/semaphore: Add nxsem_init() which is identical to sem_init() except that it never modifies the errno variable. Changed all references to sem_init in the OS to nxsem_init().
sched/semaphore: Rename sem_tickwait() to nxsem_tickwait() so that it is clear this is an internal OS function.
sched/semaphoate: Rename sem_reset() to nxsem_reset() so that it is clear this is an internal OS function.
There are two issues with it however:
1. Reading from file system on a per packet basis could be slow. I think it probably should have a small, in-memory cache of most frequently used routes for good problem.
2. Currently the delroute logic is disabled due to a problem with the design. NuttX does not currently support truncate(). Therefore, it is not possible to delete entries from the routing table file.
In this current implementation, that leaves the last entry intact at the end of the file. An alternative design might include a tag on each record to indicate if the record is valid or not. That would work but would add complexity to the other routing table functions.
The existing implementation is available for testing purposes only if CONFIG_EXPERIMENTAL=y.
Squashed commit of the following:
net/route: The current delroute design depends on file truncation. However, NuttX does not currently support truncate. Alternative, more complex designs are possible but not implemented. At present the file routing table are otherwise functional but the delroute logic is disabled via CONFIG_EXPERIMENTAL. Enable it only if you plan to fix it.
net/route: Fix some issues with locking routing table files.
net/route: Add partial implementation of delroute for the case where the routing table is in a file.
net/route: Add support for seeking to positions in the routing table.
net/route: Add net_addroute_ipv4/6() using a file-based routing table.
net/route: Add net_foreach_ipv4/4() using a file-based routing table.
net/route: Initial build, configuration, and fs utilies to support routing tables in a file.
