On Wed, 14 Sep 2016, Josh Triplett wrote: > On Wed, Sep 14, 2016 at 04:46:54PM -0400, Nicolas Pitre wrote: > > Many embedded systems typically don't need them. This removes about > > 22KB from the kernel binary size on ARM when configured out. > > > > Corresponding syscalls are routed to a stub logging the attempt to > > use those syscalls which should be enough of a clue if they were > > disabled without proper consideration. They are: timer_create, > > timer_gettime: timer_getoverrun, timer_settime, timer_delete, > > clock_adjtime. > > > > The clock_settime, clock_gettime, clock_getres and clock_nanosleep syscalls > > are replaced by simple wrappers compatible with CLOCK_REALTIME, > > CLOCK_MONOTONIC and CLOCK_BOOTTIME only. > > > > Signed-off-by: Nicolas Pitre <[email protected]> > > --- > > > > Changes from RFC/v1: > > > > - Stubbed-out functions moved to static inlines. > > - The timer signal handling code is now removed. > > - The list of removed syscalls is explicitly documented. > > - The clock_settime, clock_gettime, clock_getres and clock_nanosleep > > syscalls are minimally preserved as this required very little code. > > > > I'm now able to boot a copy of Fedora 21 with this patch and > > CONFIG_POSIX_TIMERS=n with no apparent issues. > > This looks quite reasonable. > > Does booting a standard distro really require providing clock_settime?
I don't know. Maybe some date(1) implementation uses it. It is however so small that there is no real advantage in explicitly removing it. > I'd still prefer to see the special-case sys_ni support dropped, > especially since the most common syscalls now remain. However, if > others want to see it kept, I won't object too strongly; whoever ends up > implementing a common (and optional) version of that infrastructure for > all syscalls can fold this into it. Personally, I'd prefer to see more of those configurable syscalls before introducing such infrastructure. Nicolas
