PS: I guess I should back port that Go fix to all supported Go releases? On 12 March 2017 at 21:37, Michael Hudson-Doyle < michael.hud...@canonical.com> wrote:
> Before we get into this, what is the actual problem here? Just the ugly > messages? > > On 11 March 2017 at 02:58, Alfonso Sanchez-Beato <alfonso.sanchez-beato@ > canonical.com> wrote: > >> On Fri, Mar 10, 2017 at 10:22 AM, John Lenton <john.len...@canonical.com> >> wrote: >> >> > Hello! >> > >> > We're seeing a weird issue with either go, pthreads, or the kernel. If >> > you're knowledgeable about one or more of those things, could you take >> > a look? Thank you. >> > >> > The issue manifests as nasty warnings from the "snap run" command, >> > which is also the first step into a snapped app or service. It looks >> > like >> > >> > runtime/cgo: pthread_create failed: Resource temporarily unavailable >> > >> > a very stripped-down reproducer is http://pastebin.ubuntu.com/24150663/ >> > >> > build that, run it in a loop, and you'll see a bunch of those messages >> > (and some weirder ones, but let's take it one step at a time) >> > > Turns out this was fixed in Go 1.8: https://go-review. > googlesource.com/c/33894/ > > >> > if you comment out the 'import "C"' line the message will change but >> > still happen, which makes me think that at least in part this is a Go >> > issue (or that we're holding it wrong). >> > > ... but only in the non-cgo case, you can (occasionally) still get > messages like: > > runtime: failed to create new OS thread (have 5 already; errno=11) > runtime: may need to increase max user processes (ulimit -u) > fatal error: newosproc > > if you comment out the import "C". I guess we should report that upstream. > > >> > Note that the exec does work; the warning seems to come from a >> > different thread than the one doing the Exec (the other clue that >> > points in this direction is that sometimes the message is truncated). >> > You can verify the fact that it does run by changing the /bin/true to >> > /bin/echo os.Args[1], but because this issue is obviously a race >> > somewhere, this change makes it less likely to happen (from ~10% down >> > to ~.5% of runs, in my machines). >> > >> > One thing that makes this harder to debug is that strace'ing the >> > process hangs (hard, kill -9 of strace to get out) before reproducing >> > the issue. This probably means we need to trace it at a lower level, >> > and I don't know enough about tracing a process group from inside the >> > kernel to be able to do that; what I can find about kernel-level >> > tracing is around syscalls or devices. >> > >> > Ideas? >> > >> >> I found this related thread: >> >> https://groups.google.com/forum/#!msg/golang-nuts/8gszDBRZh_ >> 4/lhROTfN9TxIJ >> >> << >> I believe this can happen on GNU/Linux if your program uses cgo and if >> thread A is in the Go runtime starting up a new thread B while thread >> C is execing a program. The underlying cause is that while one thread >> is calling exec the Linux kernel will fail attempts by other threads >> to call clone by returning EAGAIN. (Look for uses of the in_exec >> field in the kernel sources.) >> >> >> > > Yeah, this seems to be very accurate. It's also why it seems this is a > cosmetic problem only, some thread not calling exec fails, but well, the > thread is about to die anyway. > > >> Something like adding a little sleep removes the traces, for instance: >> >> http://paste.ubuntu.com/24151637/ >> >> where the program run sleep for 1ms before calling Exec. For smaller units >> (say, 20 us) the issue still happens. >> >> It looks to me that right before running main(), go creates some threads, >> calling clone() and probably getting the race described in the thread. As >> anyway you are running Exec I guess the traces are harmless, you do not >> need the go threads. Nonetheless, I think that the go run time should >> retry >> instead of printing that trace. > > > Cheers, > mwh > -- Snapcraft mailing list Snapcraft@lists.snapcraft.io Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/snapcraft
