On Wednesday 14 May 2014 16:46:29 Thomas Gleixner wrote: > On Wed, 14 May 2014, Arnd Bergmann wrote: > > > 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. > > Right, that might work with this one, but not for anything which has a > pointer to a timespec and some other argument based on long. We'd have to look at each one individually of course, but out of this list, I think it will work for most: - getitimer/setitimer - timer_settime/timer_gettime - gettimeofday/settimeofday - adjtimex - clock_gettime/clock_settime/clock_adjtime - time/stime - sysv ipc (msg, sem, shm) - fstatat (or the statx replacement once we get to that) - futimesat but not these ioctls: - socket time stamps - audio time stamps - v4l time stamps - input event time stamps > > > 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. > > On some of them yes. On i386 the u64 nsec ktime_t variant is way more > efficient. Ah, interesting. Do we have actual data for other architectures? If it's much better on x86 and never much worse anywhere else, that alone may be a reason to migrate the timestamp interfaces. 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
