> From: Laurent Vivier <laur...@vivier.eu> > Sent: Wednesday, August 28, 2019 10:51 AM > To: Josh Kunz; Aleksandar Markovic; milos.stojano...@rt-rk.com > Cc: marlies.r...@gmail.com; qemu-devel@nongnu.org; riku.voi...@iki.fi; > > qemu-triv...@nongnu.org; Peter Maydell; Shu-Chun Weng; Aleksandar Markovic > Subject: [EXTERNAL]Re: [Qemu-devel] patch to swap SIGRTMIN + 1 and SIGRTMAX - > 1 > > Le 26/08/2019 à 23:10, Josh Kunz a écrit : > > On Wed, Aug 21, 2019 at 2:28 AM Laurent Vivier <laur...@vivier.eu > > <mailto:laur...@vivier.eu>> wrote: > > > > Le 19/08/2019 à 23:46, Josh Kunz via Qemu-devel a écrit : > > > Hi all, > > > > > > I have also experienced issues with SIGRTMIN + 1, and am interested in > > > moving this patch forwards. Anything I can do here to help? Would the > > > maintainers prefer myself or Marli re-submit the patch? > > > > > > The Go issue here seems particularly sticky. Even if we update the Go > > > runtime, users may try and run older binaries built with older > > versions of > > > Go for quite some time (months? years?). Would it be better to > > hide this > > > behind some kind of build-time flag > > (`--enable-sigrtmin-plus-one-proxy` or > > > something), so that some users can opt-in, but older binaries > > still work as > > > expected? > > > > > > Also, here is a link to the original thread this message is in > > reply to > > > in-case my mail-client doesn't set up the reply properly: > > > https://lists.nongnu.org/archive/html/qemu-devel/2019-07/msg01303.html > > > > The problem here is we break something to fix something else. > > > > I'm wondering if the series from Aleksandar Markovic, "linux-user: > > Support signal passing for targets having more signals than host" [1] > > can fix the problem in a better way? > > > > > > That patch[1] (which I'll refer to as the MUX patch to avoid confusion) > > does not directly fix the issue addressed by this patch (re-wiring > > SIGRTMIN+1), but since it basically implements generic signal > > multiplexing, it could be re-worked to address this case as well. The > > way it handles `si_code` spooks me a little bit. It could easily be > > broken by a kernel version change, and such a breakage could be hard to > > detect or lead to surprising results. Other than that, it looks like a > > reasonable implementation. > > > > That said, overall, fixing the SIGRTMIN+1 issue using a more-generic > > signal-multiplexing mechanism doesn't seem *that* much better to me. It > > adds a lot of complexity, and only saves a single signal (assuming glibc > > doesn't add more reserved signals). The "big win" is additional > > emulation features, like those introduced in MUX patch (being able to > > utilize signals outside of the host range). If having those features in > > QEMU warrants the additional complexity, then re-working this patch > > on-top of that infrastructure seems like a good idea. > > > > If the maintainers want to go down that route, then I would be happy to > > re-work this patch utilizing the infrastructure from the MUX patch. > > Unfortunately it will require non-trivial changes, so it may be best to > > wait until that patch is merged. I could also provide a patch "on top > > of" the MUX patch, if that's desired/more convenient. > > > > Just one last note, if you do decide to merge the MUX patch, then it > > would be best to use SIGRTMAX (instead of SIGRTMAX-1) as the > > multiplexing signal if possible, to avoid breaking go binaries. > > > > Personally, I prefer a solution that breaks nothing. > > Aleksandar, Milos, > > do you have an updated version of you series "Support signal passing for > targets having more signals than host"? >
Milos is unfortunetely working on an entirely different project now, and can't spare enough time to finish the series. I am also busy with other issues, even though I would like very much this or equivalent solution to be integrated. Alternatively, someone in the team may have time later this year, but I do not know that yet - perhaps somebody else (Josh) can take over the series? Sincerely, Aleksandar > Thanks, > Laurent >
