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"? Thanks, Laurent
