On Mon, 30 Aug 2010, Michael Kerrisk wrote: > On Thu, Feb 5, 2009 at 2:02 AM, Davide Libenzi <davidel@xxxxxxxxxxxxxxx> wrote: > > On Thu, 5 Feb 2009, Michael Kerrisk wrote: > > > >> > Dunno. Probably try the syscall and see if it returned -EINVAL. Does > >> > that work in this case? > >> > >> As youll have seen by now, Ulrich and I noted that it works. > >> > >> > If so, it would be sensible to mention this in > >> > the description somewhere as the approved probing method and to > >> > maintain it. > >> > >> I'll add something to the man page, as this patch progresses. > > > > I see we already have stuff like this inside the man pages: > > > > O_CLOEXEC (Since Linux 2.6.23) > > Enable the close-on-exec flag for the new file descriptor. > > ... > > > > Maybe a similar note for the new flag? > > It took a while, but here's the new text in the eventfd.2 (will be in > man-pages-2.36). Could you please ACK, Davide? > > EFD_SEMAPHORE (since Linux 2.6.30) > Provide semaphore-like semantics for reads from > the new file descriptor. See below. > ... > * If EFD_SEMAPHORE was not specified and the > eventfd counter has a nonzero value, then a > read(2) returns 8 bytes containing that value, > and the counter's value is reset to zero. > > * If EFD_SEMAPHORE was specified and the eventfd > counter has a nonzero value, then a read(2) > returns 8 bytes containing the value 1, and the > counter's value is decremented by 1. Looks fine to me. - Davide
