Attempt to obtain a named mutex.
Attempts to grab a named lock exclusively, and prevents other channels from obtaining the same lock. LOCK will wait for the lock to become available. Returns
1 if the lock was obtained or
0 on error.
To avoid the possibility of a deadlock, LOCK will only attempt to obtain the lock for 3 seconds if the channel already has another lock.
This documentation was imported from Asterisk Version SVN-branch-11-r403917