On 10/1/19 10:07 AM, Florian Weimer wrote: > * Arnd Bergmann: > >> On Tue, Oct 1, 2019 at 5:38 PM Jens Axboe <axboe@xxxxxxxxx> wrote: >>> >>> On 10/1/19 8:09 AM, Jens Axboe wrote: >>>> On 9/30/19 2:20 PM, Arnd Bergmann wrote: >>>>> All system calls use struct __kernel_timespec instead of the old struct >>>>> timespec, but this one was just added with the old-style ABI. Change it >>>>> now to enforce the use of __kernel_timespec, avoiding ABI confusion and >>>>> the need for compat handlers on 32-bit architectures. >>>>> >>>>> Any user space caller will have to use __kernel_timespec now, but this >>>>> is unambiguous and works for any C library regardless of the time_t >>>>> definition. A nicer way to specify the timeout would have been a less >>>>> ambiguous 64-bit nanosecond value, but I suppose it's too late now to >>>>> change that as this would impact both 32-bit and 64-bit users. >>>> >>>> Thanks for catching that, Arnd. Applied. >>> >>> On second thought - since there appears to be no good 64-bit timespec >>> available to userspace, the alternative here is including on in liburing. >> >> What's wrong with using __kernel_timespec? Just the name? >> I suppose liburing could add a macro to give it a different name >> for its users. > > Yes, mostly the name. > > __ names are reserved for the C/C++ implementation (which does not > include the kernel). __kernel_timespec looks like an internal kernel > type to the uninitiated, not a UAPI type. > > Once we have struct timespec64 in userspace, you also end up with > copying stuff around or introducing aliasing violations. > > I'm not saying those concerns are valid, but you asked what's wrong with > it. 8-) FWIW, I do agree, __kernel_timespec sounds like an internal type, not something apps should be using. timespec64 works a lot better for that. Oh well. -- Jens Axboe
