'binder: RLIMIT_NICE not set' when using binder from the ubuntu side

[Ricardo Salveti]

http://kernel.ubuntu.com/git?p=ubuntu/ubuntu-saucy.git;a=blob;f=drivers/staging/android/binder.c;hb=refs/heads/mako#l516

"""
static void binder_set_nice(long nice)
{
 long min_nice;
 if (can_nice(current, nice)) {
  set_user_nice(current, nice);
  return;
 }
 min_nice = 20 - current->signal->rlim[RLIMIT_NICE].rlim_cur;
 binder_debug(BINDER_DEBUG_PRIORITY_CAP,
       "binder: %d: nice value %ld not allowed use "
       "%ld instead\n", current->pid, nice, min_nice);
 set_user_nice(current, min_nice);
 if (min_nice < 20)
  return;
 binder_user_error("binder: %d RLIMIT_NICE not set\n", current->pid);
}
"""

That happens because binder expects it to be able to change the nice value for the specific process, and fails when the process is started by Ubuntu, which has a default nice value of 0 (rlimit nice is set to 40 40 by default in android, via android's init).

[Ricardo Salveti (rsalveti)]

Some logs:
Jul 18 22:32:07 ubuntu-phablet kernel: [ 81.813598] binder: 1255: nice value 0 not allowed use 20 instead
Jul 18 22:32:07 ubuntu-phablet kernel: [ 81.813598] binder: 1255 RLIMIT_NICE not set
Jul 18 22:32:07 ubuntu-phablet kernel: [ 81.881927] binder: 1262: nice value -8 not allowed use 20 instead
Jul 18 22:32:07 ubuntu-phablet kernel: [ 81.881927] binder: 1262 RLIMIT_NICE not set

To reproduce:
- Stop unity8 (stop unity8)
- Start the camera-app as phablet user:
/usr/bin/camera-app -testability --fullscreen --desktop_file_hint=/usr/share/applications/camera-app.desktop

[Ricardo Salveti (rsalveti)]

The camera app uses binder to talk to the media service, which is running inside the Android container.

[Tim Gardner (timg-tpi)]

Ricardo - Andy and I don't think this is a bug. The container appears to be doing what it is designed to do, e.g., contain processes within their assigned limits. IIRC you've already written an upstart job that launches the binder with appropriate 'nice' limits, right ?

[anders3408 (anders3408)]

same thing happens on oppo find 5 builds...

[Ricardo Salveti (rsalveti)]

From camera-app:
Max nice priority 0 0
Max realtime priority 0 0

We're not setting the nice value as done by android since we flipped the container, and afaik we still don't have a policy that describes the nice priority for specific processes (system, phablet, etc).

The binder message itself is harmless, and we're ignoring it at syslog already, just annoying the kernel log buffer ring.