pthread_create failed is printed some times when running a snap

[Leo Arias]

During the past week, Alan, myself and cgull [1] have seen this error printed intermittently when we run a snap:

runtime/cgo: pthread_create failed: Resource temporarily unavailable

I'll pay more attention and update this bug if I find it again. Reporting in the meantime to see if somebody else can share more information.

[1] https://github.com/mobile-shell/mosh/pull/854#issuecomment-277424563

[Felipe Reyes (freyes)]

At the moment I'm seeing this issue with a snap I'm developing/testing, when I changed the confinement method from strict to classic the error appeared.

Some details of my system:

ii snapd 2.22.3+16.10 amd64 Tool to interact with Ubuntu Core Snappy.

$ apt-cache policy snapd
snapd:
  Installed: 2.22.3+16.10
  Candidate: 2.22.3+16.10
  Version table:
 *** 2.22.3+16.10 500
        500 http://archive.ubuntu.com/ubuntu yakkety-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     2.16+16.10ubuntu1 500
        500 http://archive.ubuntu.com/ubuntu yakkety/main amd64 Packages
$ uname -a
Linux alienware.lan 4.8.0-38-generic #41-Ubuntu SMP Wed Feb 8 14:27:17 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

This is the output when running the command:
$ bundletester -h
runtime/cgo: pthread_create failed: Resource temporarily unavailableruntime/cgo: pthread_create failed: Resource temporarily unavailable
runtime/cgo: runtime/cgo: runtime/cgo: pthread_create failed: Resource temporarily unavailable
runtime/cgo: pthread_create failed: Resource temporarily unavailableruntime/cgo: runtime/cgo: runtime/cgo: runtime/cgo: pthread_create failed: Resource temporarily unavailable
runtime/cgo: pthread_create failed: Resource temporarily unavailable
runtime/cgo: pthread_create failed: Resource temporarily unavailable
runtime/cgo: pthread_create failed: Resource temporarily unavailable
runtime/cgo: pthread_create failed: Resource temporarily unavailable
runtime/cgo: runtime/cgo: pthread_create failed: Resource temporarily unavailable
runtime/cgo: runtime/cgo: runtime/cgo: pthread_create failed: Resource temporarily unavailable
runtime/cgo: pthread_create failed: Resource temporarily unavailableruntime/cgo: pthread_create failed: Resource temporarily unavailable
runtime/cgo: pthread_create failed: Resource temporarily unavailable
runtime/cgo: runtime/cgo: pthread_create failed: Resource temporarily unavailable
runtime/cgo: runtime/cgo: pthread_create failed: Resource temporarily unavailable
runtime/cgo: runtime/cgo: runtime/cgo: runtime/cgo: pthread_create failed: Resource temporarily unavailable

I'm attaching the output of strace for the snap-confine process ( root 8504 103 0.0 13276 820 ? R 13:20 9:41 /usr/lib/snapd/snap-confine --classic snap.bundletester.bundletester /usr/lib/snapd/snap-exec bundletester -h )

[Felipe Reyes (freyes)]

After some (undetermined) time the command gave up and printed:

...
runtime/cgo: pthread_create failed: Resource temporarily unavailable
runtime/cgo: runtime/cgo: runtime/cgo: pthread_create failed: Resource temporarily unavailable
runtime/cgo: pthread_create failed: Resource temporarily unavailable
need to run as root or suid

[Felipe Reyes (freyes)]

I could make it work, I had to change the command, originally I had this:

apps:
  bundletester:
    command: bundletester

If add the prefix 'bin/' to the command, it successfully gets executed

apps:
  bundletester:
    command: bin/bundletester

I could find this as the root cause when running strace and filtering for execve syscall and I could notice how it was looping trying to run bundletester and going from the wrapper to wrapper http://pastebin.ubuntu.com/24055202/

[Zygmunt Krynicki (zyga)]

There are two bugs here (both exist separately):

- in certain situations snapcraft will create an exec loop
- pthread_create messages can be emited by certain combination of golang/kernel

I'll try to find them and dupe this bug as one of the two.