[Asterisk-code-review] sig_pri: Fix deadlock caused by sig_pri_queue_hangup (asterisk[16])

[George Joseph]

Hello Joshua Colp, Friendly Automation, 

I'd like you to reexamine a change. Please visit

    https://gerrit.asterisk.org/c/asterisk/+/13527

to look at the new patch set (#2).

Change subject: sig_pri:  Fix deadlock caused by sig_pri_queue_hangup
......................................................................

sig_pri:  Fix deadlock caused by sig_pri_queue_hangup

The change to add setting hangupsource to sig_pri_queue_hangup()
made in https://gerrit.asterisk.org/c/asterisk/+/12857 casued
deadlocks when a hangup request was received from the core at the
same time a hanguprequest was received from the remote end via the
D channel.

Although the PRI's channel private structure was being unlocked
before setting the hangupsource, the PRI's own lock was still being
held during the process.  If channel actions were also coming from
the core, a deadlock on the PRI could result.  This deadlock could
then escalate to the entire DAHDI subsystem via DAHDI's global
interface list lock, especially if someone used the PRI CLI commands.

Fix:

* We now unlock the PRI as well as the PRI's channel private
  structure before setting the hangupsource, then relock both
  afterwards.

ASTERISK-28605
Reported by: Dirk Wendland

Change-Id: Id74aaa5d4e3746063dbe9deed188eb65193cb9c9
---
M channels/sig_pri.c
1 file changed, 7 insertions(+), 1 deletion(-)


  git pull ssh://gerrit.asterisk.org:29418/asterisk refs/changes/27/13527/2
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Gerrit-Project: asterisk
Gerrit-Branch: 16
Gerrit-Change-Id: Id74aaa5d4e3746063dbe9deed188eb65193cb9c9
Gerrit-Change-Number: 13527
Gerrit-PatchSet: 2
Gerrit-Owner: George Joseph <gjoseph at digium.com>
Gerrit-Reviewer: Friendly Automation
Gerrit-Reviewer: Joshua Colp <jcolp at sangoma.com>
Gerrit-MessageType: newpatchset
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