I think I'm convinced it's worthwhile to try harder at getting cross-process channels-over-channels working. It would result in a lot less churn, for sure. The fact that they have to be transmitted out of band is an interesting serialization challenge, but it shouldn't be insurmountable.
I think the data loss I was seeing may be that kernel bug related to holding file descriptors open. Given the fact that we have kernel bugs to work around on Mac, though, I'm inclined to try using Mach ports first (and they're the system native IPC mechanism anyway). Patrick On Jun 19, 2015 8:34 AM, "Andrew McCreight" <amccrei...@mozilla.com> wrote: > On Fri, Jun 19, 2015 at 3:21 AM, Robert O'Callahan <rob...@ocallahan.org> > wrote: > > > On Fri, Jun 19, 2015 at 7:10 PM, Patrick Walton <pwal...@mozilla.com> > > wrote: > > > > > In theory you can use cmsg on POSIX systems to send channels over > > > channels, by treating channels as file descriptors. I tried this first, > > and > > > I believe it actually worked well on Linux. But on Mac I ran into all > > sorts > > > of (as far as I can tell) kernel bugs, including kernel panics and data > > > loss. It might still be possible by using Mach ports instead on the Mac > > > (and I started to sketch that code), but I eventually figured it was > > going > > > to be cleaner to just stop sending channels over channels across > process > > > boundaries. > > > > > > > Firefox IPDL sends file descriptors over sockets on Mac using cmsg. There > > is a kernel bug where an in-flight file descriptor is not kept open by > the > > kernel, so you must keep it open on the sender side until the message is > > acknowledged. I don't know about any kernel panics related to that > feature. > > > > Patrick, if you look at the various stuff in the chromium IPC directory > that is guarded by ifdef OS_MACOSX, you can see some of the workarounds. > For instance: > > http://mxr.mozilla.org/mozilla-central/source/ipc/chromium/src/chrome/common/ipc_channel_posix.cc#592 > > > > > > On Windows you should be able to rig something up using DuplicateHandle. > I > > think Firefox uses this on Windows but I'm not sure. > > > > Rob > > -- > > oIo otoeololo oyooouo otohoaoto oaonoyooonoeo owohooo oioso oaonogoroyo > > owoiotoho oao oboroootohoeoro oooro osoiosotoeoro owoiololo oboeo > > osouobojoeocoto otooo ojouodogomoeonoto.o oAogoaoiono,o oaonoyooonoeo > > owohooo > > osoaoyoso otooo oao oboroootohoeoro oooro osoiosotoeoro,o o‘oRoaocoao,o’o > > oioso > > oaonosowoeoroaoboloeo otooo otohoeo ocooouoroto.o oAonodo oaonoyooonoeo > > owohooo > > osoaoyoso,o o‘oYooouo ofooooolo!o’o owoiololo oboeo oiono odoaonogoeoro > > ooofo > > otohoeo ofoioroeo ooofo ohoeololo. > > _______________________________________________ > > dev-servo mailing list > > dev-servo@lists.mozilla.org > > https://lists.mozilla.org/listinfo/dev-servo > > > _______________________________________________ > dev-servo mailing list > dev-servo@lists.mozilla.org > https://lists.mozilla.org/listinfo/dev-servo > _______________________________________________ dev-servo mailing list dev-servo@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-servo
