On Fri, Mar 16, 2018 at 6:43 PM, Darren Hart <[email protected]> wrote: > On Thu, Mar 15, 2018 at 08:04:56PM +0100, Dominik Brodowski wrote: >> sys_futex() is a wrapper to do_futex() which does not modify any >> values here: >> >> - uaddr, val and val3 are kept the same >> >> - op is masked with FUTEX_CMD_MASK, but is always set to FUTEX_WAKE. >> Therefore, val2 is always 0. >> >> - as utime is set to NULL, *timeout is NULL >> >> Cc: Thomas Gleixner <[email protected]> >> Cc: Ingo Molnar <[email protected]> >> Cc: Peter Zijlstra <[email protected]> >> Cc: Darren Hart <[email protected]> >> Cc: Andrew Morton <[email protected]> >> Signed-off-by: Dominik Brodowski <[email protected]> > > Hi Dominik, > > I'm missing the "why" part here. What is it you are trying to address? > > do_futex is not currently in use outside of the futex implementation, > while sys_futex is. This decouples the interface from the > implementation. While this is perhaps less critical within the > kernel, I don't see a compelling reason to increase the coupling > between the mm and futex implementations. > > Without a compelling WHY, Nack from me. >
We want to make some changes to the way that the syscall entry code invokes syscalls, and these changes will make it impossible to call sys_xyz() functions from the kernel. So we can make sys_futex() be a trivial wrapper around a new ksys_futex(), or we can do a patch like this.
