The 32-Bit Semaphore Event and Mutex Semaphores

Block ids for 32-bit sems point to kernel heap allocated structure with object mnemonic semstruc.

.PB under the KDB usually identifies these as SEM32, but DF doesn't.

.D SEM32 will format a 32-bit semaphore structure.

There are several structures that relate to 32-bit semaphores. Each of these is allocated from the kernel heaps and is assigned the following meaningful owner id mnemonics:

semmuxq (0xffbe)

Semaphore Mux Queue. This records instances of single event or mutex semaphores being also waited on in a mux wait.
semopenq (0xffbf)
Semaphore Open Queue. This tracks all processes that have opened a 32-bit semaphore.
semrec (0xffc0)
SemRecord. This is a system copy of the user's SemRecord structure, which was created when a Mux wait was declared. It correlates user semaphore Ids with semaphore handles.
semstr (0xffc1)
The semaphore name string.
semstruc (0xffc2)
The main 32-bit structure. The address of this forms the BlockId when a thread waits on a 32-bit semaphore.
Of the associated structures listed above the Open Queue and Mux Queue may be formatted using:

• D OPENQ

• D MUXQ

In this example we look at the BlockId slot 42 is waiting on.

# .p 42 Slot  Pid  Ppid Csid Ord  Sta Pri  pTSD     pPTDA    pTCB     Disp SG Name 0042  000d 000a 000d 0002 blk 0200 7bd1a000 7bdfa188 7bddfe20 0ed4 11 PMSHL32

# .pb42
 Slot  Sta BlockID  Name     Type        Addr        Symbol
 0042  blk fe0bf91c PMSHL32

>> check owner of blockid
# .m %fe0bf91c

*har     par      cpg        va    flg next prev link hash hob   hal
 0003 %fef1f04c 00001000 %fdf1f000 001 0002 0020 0000 0000 0003 0000      =0000
 hob   har hobnxt flgs own  hmte  sown,cnt lt st xf
 0003  0003 ff08  0000 ffec 0000  0000 00  06 00 00 vmkrhrw

>> kernel swappable heap. Check current user of heap block.

# dd  %fe0bf91c-10
%fe0bf90c  ffbf000c 00010008 fe0bff20 ffc20014
%fe0bf91c  00000011 00000000 fef1ef94 fcae5a28
%fe0bf92c  ffbf0010 00010006 fe08f24c fe0bf92e
%fe0bf93c  ffbf000c 00010006 fe08f7c0 ffa4000c
%fe0bf94c  fe0567d0 00010494 ffbf000c 0001000a
%fe0bf95c  00000000 ffa4000c fe0bf970 000104ec
%fe0bf96c  ffa4000c fef1ef4c 000200ba ffbf000c
%fe0bf97c  00010005 fe0bf758 ffbf000c 00010005

# .mo ffc2
ffc2 semstruc

>> This is a 32-bit Semaphore

# .d sem32 %fe0bf91c
        Type: Shared Event
       Flags: Reset
       pMuxQ: 00000000
  Post Count: 0000
      pOpenQ: fef1ef94
       pName: fcae5a28
 Create Addr: ffbf0010

# .d openq %fef1ef94

  PID   Open Count
  ----------------
  000d     0001
  000a     0001

# da %fcae5a28
%fcae5a28 WORKPLAC\LAZYWRIT.SEM

>> For interest look for the owner of the OPENQ:

# .m %fef1ef94
*har     par      cpg        va    flg next prev link hash hob   hal
 0003 %fef1f04c 00001000 %fdf1f000 001 0002 0020 0000 0000 0003 0000      =0000
 hob   har hobnxt flgs own  hmte  sown,cnt lt st xf
 0003  0003 ff08  0000 ffec 0000  0000 00  06 00 00 vmkrhrw

# dd %fef1ef94 -10
%fef1ef84  00000000 00000000 fef10001 ffbf000c
%fef1ef94  0001000d fe0bf958 ffc20018 00000009
%fef1efa4  00000000 00000000 fef1ef58 fcb18478
%fef1efb4  ffbf000c 0001000d 00000000 ffc20018
%fef1efc4  00000009 00000000 00000000 fef1efb8
%fef1efd4  fcb18458 ff910024 00000007 00000000
%fef1efe4  00000000 00000000 00000000 00000000
%fef1eff4  00000000 00000000 ffea0004 fef2a128
# .mo ffbfffbf semopenq

>> For interest look for the owner of the pName:

# .m  %fcae5a28

*har     par      cpg        va    flg next prev link hash hob   hal
 0021 %fef1f2e0 00001400 %fca5f000 121 0020 0022 0000 0020 0022 0000      =0000
 hob   har hobnxt flgs own  hmte  sown,cnt lt st xf
 0022  0021 0000  0225 ffef 0000  0000 00  04 00 00 vmkshrw
# dd  %fcae5a28-10
%fcae5a18  003f1d1a 0007004a 52000020 0000ffc1
%fcae5a28  4b524f57 43414c50 5a414c5c 49525759
%fcae5a38  45532e54 5412004d 520000c8 0000ff60
%fcae5a48  005d004a 1b131b12 1b151b14 1b171b16
%fcae5a58  1b191b18 1b1b1b1a 1b1d1b1c 1b1f1b1e
%fcae5a68  1b211b20 1b231b22 1b251b24 1b271b26
%fcae5a78  1b291b28 1b2b1b2a 1b2d1b2c 1b2f1b2e
%fcae5a88  1b311b30 1b331b32 1b351b34 1b371b36

# .mo ffc1
ffc1 semstr

---

[Back: The Kernel Semaphore (KSEM)]
[Next: PMSEM/GRESEM]