The following list is a small selection of global symbols from PMMERGE.SYM that will be of help in locating the structures associated with message handling:

pmsemaphores

This is the label for the table of PMSEM and GRESEM semaphore structures. Offset +0x20 is the location of the User Semaphore. If this is owned and not released within the time-out period after Cltrl-Esc has been hit, then the Application Not Responding to Messages reports the semaphore owner as the culprit.
pmqSyslock
The PMQ of the thread that has locked the system queue.

This is the first place to look when investigating a hang in a PM application. The system uses this to name a bad application when the Application Not Responding to Messages dialog appears.

pmqFocus
The PMQ of the window that has the focus.

if pmqSyslock is zero, the system uses this as a second choice for the bad application when the Application Not Responding to Messages dialog appears.

pmqKeyWake
The PMQ of the current keyboard event receiver.
pmqMouseWake
The PMQ of the current mouse event receiver.
pmqEventWake
The PMQ of the current miscellaneous event receiver.
pwndFocus
The PWND of the window currently in focus.
pmqShutdown
The PMQ of the thread sent a WM_QUIT and being waited on to terminte. If Shutdown doesn't complete, then this could be a good place to start investigation of the problem.
pmqCapture
The PMQ of the thread that has the mouse captured.
pwndCapture
The PWND of the window associated with mouse capture.
pwndSysModal
The PWND of the System Modal window.
pmqVisLock
The PMQ that has visible regions locked.
pmqTrack
The PMQ of the thread currently in WinTrackRect.
pmqLockUpdate
The PMQ of the thread that has update locked.
pHandleTable
The address of the handle table.
pSysqueue
The MQ of the system input queue.

The system queue is headed by a partial MQ since it does not require the fields to support a receive list.

pmqShell
The PMQ of the 1st thread of the 1st Shell Process.

This thread is responsible for starting and re-starting the Workplace Shell.

pmqShell2
The PMQ of the 1st thread of the 2nd Shell or Workplace Shell Process.

This thread is the main thread of the desktop PM application.

paAABRegs
The address of the application anchor block registers (AAB).

AAB registers are allocated for each PM application message thread. This is located in thread local memory, which implies that it is correct only for the current thread context. The Thread Local Memory Area is saved in the TCB and restored when the thread is made current. Since the TCB may be located in System storage under any context then a thread's PMQ may be found in any context from its TCB.

pwndObject
The PWND of the Object Window.

This is the parent or owner of all non-display windows.

pwndDesktop
The PWND of the Desktop Window.

This is the parent of owner of all displayable windows.

SleepPMQ+nnn
When a thread is blocked at approximately offset +0x155 into SleepPMQ then it is waiting on the message queue semaphore for new messages or responses to outstanding sent messages. Offset +0x30 from the current stack pointer usually contains the PMQ for the current thread.
pmqList
All MQs are chained on a single linked master list from offset +0x0 of the MQ. The current head of the master list is pointed to by pmqList.
psmsList
All SMSs are chained on a single linked master list from offset +0x0 of the SMS. The current head of the master list is pointed to by psmsList.
qhpsBadApp
This is the label of the QHPSTRUCT saved the first time a time-out occurs after Ctrl-Esc has been hit and the Application Not Responding to Messages dialog appears.
fBadAppDialog
A Boolean that indicates when the Application Not Responding to Messages dialog has been displayed.

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