#2420 imm: IMMND on PL hangs when headless

[Hung Nguyen]

IMMND on PL hangs at waitpid() after coordinator removal.

When pbe process is in D State (Uninterruptible sleep (usually IO)), waitpid() will be hung if WNOHANG is not specified.

    LOG_WA("SC were absent and PBE appears hung, sending SIGKILL");
    kill(cb->pbePid, SIGKILL);
    waitpid(cb->pbePid, NULL, 0);

The bug is introduced by [#2296].

Solution: Use waitpid() with WNOHANG specified. Check for pbe/sync process exiting before sending introduce message during headless.

[Hung Nguyen]

5.17.08 (develop) [code:11325e]

commit 11325e3b7643c4d0500771ef7e022fcc47f1d31a
Author: Hung Nguyen <hung.d.nguyen@dektech.com.au>
Date:   Thu Apr 20 14:37:18 2017 +0700

    imm: Use waitpid with WNOHANG to check for sync process and pbe process [#2420]

    Use waitpid with WNOHANG to check for sync process and pbe process.
    The processes are checked before resending the intro message.
    The intro message is only sent when those processes exit.

5.17.06 (release) [code:51233a]

commit 51233a54a11809ac48e27c043361b0ac95c5b71a
Author: Hung Nguyen <hung.d.nguyen@dektech.com.au>
Date:   Thu Apr 20 14:37:18 2017 +0700

    imm: Use waitpid with WNOHANG to check for sync process and pbe process [#2420]

    Use waitpid with WNOHANG to check for sync process and pbe process.
    The processes are checked before resending the intro message.
    The intro message is only sent when those processes exit.

default (mecurial) [staging:2aa1ed]

changeset:   8773:2aa1edbd41e9
user:        Hung Nguyen <hung.d.nguyen@dektech.com.au>
date:        Tue Apr 11 19:05:48 2017 +0700
summary:     imm: Use waitpid with WNOHANG to check for sync process and pbe process [#2420]