* Simplify EINTR/ECANCEL error handling
1. Add semaphore uninterruptible wait function
2 .Replace semaphore wait loop with a single uninterruptible wait
3. Replace all sem_xxx to nxsem_xxx
* Unify the void cast usage
1. Remove void cast for function because many place ignore the returned value witout cast
2. Replace void cast for variable with UNUSED macro
sched/wqueue: Modify high priority work queue to support multiple threads.
sched/wqueue and libs/libc/wqueue: workqueues don't need set global data to zero since .bss is cleared automatically. Removing this unnecessary initialization also avoids the loss the work items queued before initialization.
Squashed commit of the following:
sched: Rename all use of system_t to clock_t.
syscall: Rename all use of system_t to clock_t.
net: Rename all use of system_t to clock_t.
libs: Rename all use of system_t to clock_t.
fs: Rename all use of system_t to clock_t.
drivers: Rename all use of system_t to clock_t.
arch: Rename all use of system_t to clock_t.
include: Remove definition of systime_t; rename all use of system_t to clock_t.
Squashed commit of the following:
Change all calls to usleep() in the OS proper to calls to nxsig_usleep()
sched/signal: Add a new OS internal function nxsig_usleep() that is functionally equivalent to usleep() but does not cause a cancellaption point and does not modify the errno variable.
sched/signal: Add a new OS internal function nxsig_sleep() that is functionally equivalent to sleep() but does not cause a cancellaption point.
sigtimedwait() -> nxsig_timedwait()
sigwaitinfo() -> nxsig_waitinfo()
nanosleep() -> nxsig_nanosleep()
The internal OS versions differ from the standard application interfaces in that:
- They do not create cancellation points, and
- they do not modify the application's errno variable
Squashed commit of the following:
sched/signal: Replace all usage of sigwaitinfo(), sigtimedwait(), and nanosleep() with the OS internal counterparts nxsig_waitinfo(), nxsig_timedwait(), and nxsig_nanosleep().
sched/signal: Add nxsig_nanosleep(). This is an internal OS version of nanosleep(). It differs in that it does not set the errno varaiable and does not create a cancellation point.
sched/signal: Add nxsig_timedwait() and nxsig_waitinfo(). These are internal OS versions of sigtimedwait() and sigwaitinfo(). They differ in that they do not set the errno varaiable and they do not create cancellation points.
