On 2/1/20 2:16 PM, Pavel Begunkov wrote: > On 01/02/2020 20:52, Jens Axboe wrote: >> On 2/1/20 10:49 AM, Andres Freund wrote: >>> Hi, >>> >>> On February 1, 2020 6:39:41 PM GMT+01:00, Jens Axboe <axboe@xxxxxxxxx> wrote: >>>> On 2/1/20 5:53 AM, Andres Freund wrote: >>>>> Hi, >>>>> >>>>> As long as the syscalls aren't exposed by glibc it'd be useful - at >>>>> least for me - to have liburing expose the syscalls without really >>>> going >>>>> through liburing facilities... >>>>> >>>>> Right now I'm e.g. using a "raw" >>>> io_uring_enter(IORING_ENTER_GETEVENTS) >>>>> to be able to have multiple processes safely wait for events on the >>>> same >>>>> uring, without needing to hold the lock [1] protecting the ring [2]. >>>> It's >>>>> probably a good idea to add a liburing function to be able to do so, >>>> but >>>>> I'd guess there are going to continue to be cases like that. In a bit >>>>> of time it seems likely that at least open source users of uring that >>>>> are included in databases, have to work against multiple versions of >>>>> liburing (as usually embedding libs is not allowed), and sometimes >>>> that >>>>> is easier if one can backfill a function or two if necessary. >>>>> >>>>> That syscall should probably be under a name that won't conflict with >>>>> eventual glibc implementation of the syscall. >>>>> >>>>> Obviously I can just do the syscall() etc myself, but it seems >>>>> unnecessary to have a separate copy of the ifdefs for syscall numbers >>>>> etc. >>>>> >>>>> What do you think? >>>> >>>> Not sure what I'm missing here, but liburing already has >>>> __sys_io_uring_enter() for this purpose, and ditto for the register >>>> and setup functions? >>> >>> Aren't they hidden to the outside by the symbol versioning script? >> >> So you just want to have them exposed? I'd be fine with that. I'll >> take a patch :-) >> > > Depends on how it's used, but I'd strive to inline > __sys_io_uring_enter() to remove the extra indirect call into the > shared lib. Though, not sure about packaging and all this stuff. May > be useful to do that for liburing as well. Not sure that actually matters when you're doing a syscall anyway, that should be the long pole for the operation. -- Jens Axboe
