On Wednesday 14 May 2014 14:21:48 Thomas Gleixner wrote: > > So in the 32-on-64 case we'll have two compat variants: > > SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val, > struct timespec __user *, utime, u32 __user *, uaddr2, > u32, val3) > > COMPAT_SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val, > struct compat_timespec __user *, utime, u32 __user *, uaddr2, > u32, val3) > > COMPAT_SYSCALL_DEFINE6(futex64, u32 __user *, uaddr, int, op, u32, val, > struct timespec64 __user *, utime, u32 __user *, uaddr2, > u32, val3) > > The native 64bit futex64 syscall is mapped to futex. I was actually hoping that we could map the compat futex64 to futex as well here, since 64-bit timespec and compat timespec64 would be the same structure. > And for a 32bit kernel you have two > > SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val, > struct timespec __user *, utime, u32 __user *, uaddr2, > u32, val3) > > SYSCALL_DEFINE6(futex64, u32 __user *, uaddr, int, op, u32, val, > struct timespec64 __user *, utime, u32 __user *, uaddr2, > u32, val3) And here, we could think about renaming the kernel internal symbols so that we use the same two definitions as well, one for compat_timespec and one for timespec64. Those are details we don't need to debate now. > Fine with me, but we really need to discuss the timespec64 with user > space folks. Definitely. > I'm curious, whether quite some code, like high frequency timestamps > wouldn't be better of with a strict 64 bit nanosecond granular time > represenation. At least in the kernel, I think ktime_t is already the right type to use on both 64-bit and 32-bit architectures as it can be slow to extract the seconds portion of 64-bit nanoseconds on a 32-bit machine. FWIW, 64-bit ns gives us 584 years worth of nanoseconds, which means none of us or the people we know will be around before this becomes a problem ;-) For the user interface, we can decide which representation to use for each syscall individually depending on the needs. We should just not have to many different variants. I was going for timespec64 just because that would allow us to keep the 64-bit kernel ABI unchanged. > I often enough cursed timespec for clock_nanosleep on an absolute > timeline. I need to go through all that normalizing stuff instead of > just doing next_event += 500000; And all user space needs to do it too. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
