Date: Wed, 6 Jul 2016 21:43:54 -0700 (PDT) From: Don Lewis <truckman@FreeBSD.org> To: mmacy@nextbsd.org Cc: freebsd-current@freebsd.org, freebsd-hackers@freebsd.org Subject: Re: difference in SIGCHLD behavior between Linux and FreeBSD breaks apt Message-ID: <201607070443.u674hsgK007808@gw.catspoiler.org> In-Reply-To: <155c3a25e3f.11fb4143170445.2284890475527649192@nextbsd.org>
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On 6 Jul, Matthew Macy wrote: > As a first step towards managing linux user space in a chrooted > /compat/linux, initially for i915 testing with intel gpu tools, later > on to get widevine and steam to work I'm trying to get apt to work. > I've fixed a number of issues to date in pseudofs/linprocfs but now > I'm running in to a bug caused by differences in SIGCHLD handling > between Linux and FreeBSD. The situation is that apt will spawn dpkg > and wait on a pipe read. On Linux when dpkg exits the SIGCHLD to apt > causes a short read on the pipe which lets apt then continue. On > FreeBSD a SIGCHLD is silently ignored. I've even experimented with > doing a kill -20 <apt pid> to no effect. > > It would be easy enough to check sysvec against linux in pipe_read and > break out of the loop when it's awakened from msleep (assuming there > aren't deeper issues with signal propagation for anything other than > SIGINT/SIGKILL) and then do a short read. However, I'm assuming that > anyone who has worked in this area probably has a cleaner solution. It shoulds like SA_RESTART is set in sa_flags for SIGCHLD but shouldn't be in this case.
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