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HP OpenVMS System Services Reference Manual
If you are creating a new lock, the resnam argument
should be specified because the default value for the
resnam argument produces an error when it is used to
create a lock. The resnam argument is ignored for lock
conversions.
parid
| OpenVMS usage: |
lock_id |
| type: |
longword (unsigned) |
| access: |
read only |
| mechanism: |
by value |
Lock identification of the parent lock. The parid
argument is a longword containing this identification value.
If you do not specify this argument or specify it as 0, $ENQ assumes
that the lock does not have a parent lock. This argument is optional
for new locks and is ignored for lock conversions.
astadr
| OpenVMS usage: |
ast_procedure |
| type: |
procedure value |
| access: |
call without stack unwinding |
| mechanism: |
by 32- or 64-bit reference |
AST service routine to be executed when the lock is either granted or
converted. The astadr argument is the 32- or 64-bit
address of this routine. The AST is also delivered when the lock or
conversion request is canceled. Cancellation occurs if you use $DEQ
with the cancel modifier or if the waiting request is chosen to break a
deadlock.
If you specify the astadr argument, the AST routine
executes at the same access mode as the caller of $ENQ.
astprm
| OpenVMS usage: |
user_arg |
| type: |
quadword (unsigned) |
| access: |
read only |
| mechanism: |
by value |
AST parameter to be passed to the AST routine specified by the
astadr argument. The astprm argument
specifies this quadword parameter.
blkast
| OpenVMS usage: |
ast_procedure |
| type: |
procedure value |
| access: |
call without stack unwinding |
| mechanism: |
by 32- or 64-bit reference |
Blocking AST routine to be called whenever this lock is granted and is
blocking any other lock requests. The blkast argument
is the 32- or 64-bit address of this routine. Locks that are converting
to a new mode, but that are not yet granted in the new mode, do not
receive blocking ASTs.
You can pass a parameter to this routine by using the
astprm argument.
acmode
| OpenVMS usage: |
access_mode |
| type: |
longword (unsigned) |
| access: |
read only |
| mechanism: |
by value |
Access mode to be associated with the resource name. The
acmode argument indicates the least privileged access
mode from which locks can be queued on the resource.
This argument does not affect the access mode associated with the lock
or its blocking and completion ASTs. The acmode
argument is a longword containing the access mode. The $PSLDEF macro
defines the following symbols for the four access modes:
| Symbol |
Access Mode |
|
PSL$C_KERNEL
|
Kernel
|
|
PSL$C_EXEC
|
Executive
|
|
PSL$C_SUPER
|
Supervisor
|
|
PSL$C_USER
|
User
|
The $ENQ service associates an access mode with the lock in the
following way:
- If you specified a parent lock (with the parid
argument), $ENQ uses the access mode associated with the parent lock
and ignores both the acmode argument and the caller's
access mode.
- If the lock has no parent lock (you did not specify the
parid argument or specified it as 0), $ENQ uses the
least privileged of the caller's access mode and the access mode
specified by the acmode argument. If you do not
specify the acmode argument, $ENQ uses the caller's
access mode.
rsdm_id
| OpenVMS usage: |
longword |
| type: |
longword (unsigned) |
| access: |
read only |
| mechanism: |
by value |
Resource domain identification. The rsdm_id argument
is a longword specifying the resource domain association through which
a new lock is to be taken. This argument is ignored for lock
conversions and sublocks (parid is nonzero). Valid
resource domain identifiers are returned from the $SET_RESOURCE_DOMAIN
service, or by the constants RSDM$K_SYSTEM_RSDM_ID or
RSDM$K_PROCESS_RSDM_ID, which are defined by the $RSDMDEF macro in
STARLET.
nullarg
| OpenVMS usage: |
null_arg |
| type: |
longword (unsigned) |
| access: |
read only |
| mechanism: |
by value |
Placeholding argument reserved by HP.
Description
The Enqueue Lock Request service queues a new lock or lock conversion
on a resource. The $ENQ service completes asynchronously; that is, it
returns to the caller after queuing the lock request without waiting
for the lock to be either granted or converted. For synchronous
completion, use the Enqueue Lock Request and Wait ($ENQW) service. The
$ENQW service is identical to the $ENQ service in every way except that
$ENQW returns to the caller when the lock is either granted or
converted.
The $ENQ service uses system dynamic memory for the creation of the
lock and resource blocks.
When $ENQ queues a lock request, it returns the status of the request
in R0 and writes the lock identification of the lock in the lock status
block. Then, when the lock request is granted, $ENQ writes the final
completion status in the lock status block, sets the event flag, and
calls the AST routine if this has been requested.
When $ENQW queues a lock request, it returns status in R0 and in the
lock status block when the lock has been either granted or converted.
Where applicable, it simultaneously sets the event flag and calls the
AST routine.
Invalidation of the Lock Value Block
In some situations, the lock value block can become invalid. In these
situations, $ENQ warns the caller by returning the condition value
SS$_VALNOTVALID in the lock status block, provided the caller has
specified the flag LCK$M_VALBLK in the flags argument.
The SS$_VALNOTVALID condition value is a warning message, not an error
message; therefore, the $ENQ service grants the requested lock and
returns this warning on all subsequent calls to $ENQ until either a new
lock value block is written to the lock database or the resource is
deleted. Resource deletion occurs when no locks are associated with the
resource.
The following events can cause the lock value block to become invalid:
- If any process holding a protected write or exclusive mode lock on
a resource is terminated abnormally or exits before explicitly
dequeuing the lock or converting it to a lover-level lock mode, the
lock value block becomes invalid.
- If a process holding a protected write or exclusive mode lock on
the resource calls the Dequeue Lock Request ($DEQ) service to dequeue
this lock and specifies the flag LCK$M_INVVALBLK in the
flags argument, the lock value block maintained in the
lock database is marked invalid.
- If a node in an OpenVMS Cluster system fails, and a process on that
node was holding or might have been holding a protected write or
exclusive mode lock on the resource, the lock value block becomes
invalid.
This situation is dependant on which cluster node is the
master node for the resource. The following describes the two ways in
which this situation can arise:
- If a node was holding a protected write or exclusive mode lock on
the resource:
If the node that failed was not the master of the
resource tree, the master node will know what locks were held by the
node that failed. These locks will be removed from the resource and if
a removed lock was for protected write or exclusive mode, the lock
value block becomes in valid.
- If a node might have been holding a protected write or exclusive
mode lock on the resource:
If the node that failed was the master
of the resource, a remaining node in the cluster will become the new
master. If the new master finds that all granted locks on the resource
were for null mode locks or for concurrent read locks, or for both,
then the new master does not know if the failed node held a protected
write or exclusive mode lock. The lock value block will be set to
invalid in this case.
If the resource has any granted lock with a
mode other than null mode or concurrent read, then the failed node
could not have held a protected write or exclusive mode lock, and the
lock value block will not be marked as invalid.
Invalidation of the Extended Lock Value Block
The extended lock value block can be marked invalid in the following
situation: If a program updates the lock block specifying only
LCK$M_VALBLK without LCK$M_XVALBLK, only the first 16 bytes of the lock
value block will be written. The remaining 48 bytes will not be
modified. A reader who, in the future, specifies the LCK$M_XVALBLK flag
in the $ENQ system service call will be be given all 64 bytes but will
receive the warning status SS$_XVALNOTVALID flag.
If the entire lock status block is invalid as described in
Invalidation of the Lock Value Block, the SS$_VALNOTVALID status will be returned, overriding
the SS$_XVALNOTVALID status.
Required Access or Privileges
To queue a lock on a systemwide resource, the calling process must
either have SYSLCK privilege or be executing in executive or kernel
mode.
To specify a parent lock when queuing a lock, the access mode of the
caller must be equal to, or less privileged than, the access mode
associated with the parent lock.
To queue a lock conversion, the access mode associated with the lock
being converted must be equal to, or less privileged than, the access
mode of the calling process.
Required Quota
- Enqueue limit (ENQLM) quota
- AST limit (ASTLM) quota in lock conversion requests that you
specify either the astadr or blkast
argument
Related Services
$DEQ, $ENQW, $GETLKI, $GETLKIW, $SET_RESOURCE_DOMAIN
Condition Values Returned
|
SS$_NORMAL
|
The service completed successfully; the lock request was successfully
queued.
|
|
SS$_SYNCH
|
The service completed successfully; the LCK$M_SYNCSTS flag in the
flags argument was specified, and $ENQ was able to
grant the lock request immediately.
|
|
SS$_ACCVIO
|
The lock status block or the resource name cannot be read.
|
|
SS$_BADPARAM
|
You specified an invalid lock mode in the
lkmode argument.
|
|
SS$_CVTUNGRANT
|
You attempted a lock conversion on a lock that is not currently granted.
|
|
SS$_EXDEPTH
|
The limit of levels of sublocks has been exceeded.
|
|
SS$_EXENQLM
|
The process has exceeded its enqueue limit (ENQLM) quota.
|
|
SS$_INSFMEM
|
The system dynamic memory is insufficient for creating the necessary
data structures.
|
|
SS$_IVBUFLEN
|
The length of the resource name was either 0 or greater than 31.
|
|
SS$_IVLOCKID
|
You specified an invalid or nonexistent lock identification, or the
lock identified by the lock identification has an associated access
mode that is more privileged than the caller's, or the access mode of
the parent was less privileged than that of the caller.
|
|
SS$_NOLOCKID
|
No lock identification was available for the lock request.
|
|
SS$_NOSYSLCK
|
The LCK$M_SYSTEM flag in the
flags argument was specified, but the caller lacks the
necessary SYSLCK privilege.
|
|
SS$_NOTQUEUED
|
The lock request was not queued; the LCK$M_NOQUEUE flag in the
flags argument was specified, and $ENQ was not able to
grant the lock request immediately.
|
|
SS$_PARNOTGRANT
|
The parent lock specified in the
parid argument was not granted.
|
Condition Values Returned in the Lock Status Block
|
SS$_NORMAL
|
The service completed successfully; the lock was successfully granted
or converted.
|
|
SS$_ABORT
|
The lock was dequeued (by the $DEQ service) before $ENQ could grant the
lock.
|
|
SS$_CANCEL
|
The lock conversion request has been canceled and the lock has been
regranted at its previous lock mode. This condition value is returned
when $ENQ queues a lock conversion request, the request has not been
granted yet (it is in the conversion queue), and, in the interim, the
$DEQ service is called (with the LCK$M_CANCEL flag specified) to cancel
this lock conversion request. If the lock is granted before $DEQ can
cancel the conversion request, the call to $DEQ returns the condition
value SS$_CANCELGRANT, and the call to $ENQ returns SS$_NORMAL.
|
|
SS$_DEADLOCK
|
A deadlock was detected.
|
|
SS$_ILLRSDM
|
The operation attempted is not allowed on the resource. Use SHOW
SECURITY to verify the access allowed to the specified resource domain.
|
|
SS$_NODOMAIN
|
The RSDM_ID argument passed to the $ENQ call either does not correspond
to a valid resource domain for your process, or the system is not
running the audit server process.
|
|
SS$_VALNOTVALID
|
The lock value block is marked invalid. This warning message is
returned only if the caller has specified the flag LCK$M_VALBLK in the
flags argument. Note that the lock has been
successfully granted despite the return of this warning message. For a
complete discussion of lock value block invalidation, see the
Description section.
|
|
SS$_XVALNOTVALID
|
The extended value block has been marked invalid because the previous
writer has written the value block without specifying the LCK$M_XVALBLK
flag. This warning message is returned only if the caller has specified
the LCK$M_XVALBLK flag in the
flags argument. Note that the lock is successfully
granted despite the return of this warning message.
For a detailed discussion of extended lock value block
invalidation, see the section Invalidation of the Extended Lock Value Block.
|
$ENQW
Queues a lock on a resource. The $ENQW service completes synchronously;
that is, it returns to the caller when the lock has been either granted
or converted. For asynchronous completion, use the Enqueue Lock Request
($ENQ) service; $ENQ returns to the caller after queuing the lock
request, without waiting for the lock to be either granted or
converted. In all other respects, $ENQW is identical to $ENQ. See the
$ENQ description for all other information about the $ENQW service.
For additional information about system service completion, see the
Synchronize ($SYNCH) service documentation.
The $ENQ, $ENQW, $DEQ, and $GETLKI services together provide the user
interface to the Lock Management facility.
On Alpha and Integrity server systems, this service accepts 64-bit
addresses.
Format
SYS$ENQW [efn] ,lkmode ,lksb ,[flags] ,[resnam] ,[parid] ,[astadr]
,[astprm] ,[blkast] ,[acmode] ,[rsdm_id]
C Prototype
int sys$enqw (unsigned int efn, unsigned int lkmode, struct _lksb
*lksb, unsigned int flags, void *resnam, unsigned int parid, void
(*astadr)(__unknown_params), unsigned __int64 astprm, void
(*blkast)(__unknown_params), unsigned int acmode, unsigned int
rsdm_id,...);
$ENTER
The Enter service inserts a file name in a directory.
For additional information about this service, see to the OpenVMS Record Management Services Reference Manual.
$ERAPAT
Generates a security erase pattern.
Format
SYS$ERAPAT [type] ,[count] ,[patadr]
C Prototype
int sys$erapat (int type, unsigned int count, unsigned int *patadr);
Arguments
type
| OpenVMS usage: |
longword_unsigned |
| type: |
longword (unsigned) |
| access: |
read only |
| mechanism: |
by value |
Type of storage to be written over with the erase pattern. The
type argument is a longword containing the type of
storage.
The three storage types, together with their symbolic names, are
defined by the $ERADEF macro and are listed in the following table:
| Storage Type |
Symbolic Name |
|
Main memory
|
ERA$K_MEMORY
|
|
Disk
|
ERA$K_DISK
|
|
Tape
|
ERA$K_TAPE
|
count
| OpenVMS usage: |
longword_unsigned |
| type: |
longword (unsigned) |
| access: |
read only |
| mechanism: |
by value |
Number of times that $ERAPAT has been called in a single security erase
operation. The count argument is a longword containing
the iteration count.
You should call the $ERAPAT service initially with the
count argument set to 1, the second time with the
count argument set to 2, and so on, until the status
code SS$_NOTRAN is returned.
patadr
| OpenVMS usage: |
longword_unsigned |
| type: |
longword (unsigned) |
| access: |
write only |
| mechanism: |
by reference |
Security erase pattern to be written. The patadr
argument is the address of a longword into which the security erase
pattern is to be written.
Description
The Get Security Erase Pattern service generates a security erase
pattern that can be written into memory areas containing outdated but
sensitive data to make it unreadable. This service is used primarily by
the operating system, but it can also be used by users who want to
perform security erase operations on foreign disks.
You should call the $ERAPAT service iteratively until the completion
status SS$_NOTRAN is returned.
The following example demonstrates how to use the $ERAPAT service to
perform a security erase to a disk. Note that, after each call to
$ERAPAT, a test for the status SS$_NOTRAN is made. If SS$_NOTRAN has
not been returned, $QIO is called to write the pattern returned by
$ERAPAT onto the disk. After this write, $ERAPAT is called again and
the cycle is repeated until the code SS$_NOTRAN is returned, at which
point the security erase procedure is complete.
; Code fragment that erases 20 blocks (blocks 15 through 34) on a disk
;
PATTERN:
.LONG 0 ; Cell to contain output from $ERAPAT
CHANNEL:
.WORD 0 ; Channel assigned to disk device
DEVICE: .ASCID /DISK:/ ; Disk device name
.
.
.
$ASSIGN_S DEVNAM=DISK,- ; Assign a channel to the device
CHAN=CHANNEL
BLBC RO, EXIT ; Branch if error
.
.
.
MOVL #1, R2 ; Set initial count
$ERADEF ; Macro to define names
; used by $ERAPAT
10$: $ERAPAT_S - ; Call the $ERAPAT service
COUNT=R2,-
TYPE=#ERA$K_DISK,-
PATADR=PATTERN
BLBC R0, EXIT ; Branch if error
CMPL #SS$_NOTRAN, R0 ; Are we done?
BEQL EXIT ; Branch if so
$QIO_S CHAN=CHANNEL,-
FUNC=#I0$_WRITELBLK!IO$M_ERASE,- ; Call
P1=PATTERN,- ; to the $QIO service
P2=#<20*512>,- ; to write the erase
P3=#15 ; pattern
INCL R2 ; Increase count
BRB 10$
EXIT: .
.
.
|
Required Access or Privileges
None.
Required Quota
None.
Related Services
$ADD_HOLDER, $ADD_IDENT, $ASCTOID, $CHECK_ACCESS, $CHKPRO, $CREATE_RDB,
$FIND_HELD, $FIND_HOLDER, $FINISH_RDB, $FORMAT_ACL, $FORMAT_AUDIT,
$GET_SECURITY, $GRANTID, $HASH_PASSWORD, $IDTOASC, $MOD_HOLDER,
$MOD_IDENT, $MTACCESS, $PARSE_ACL, $REM_HOLDER, $REM_IDENT, $REVOKID,
$SET_SECURITY
Condition Values Returned
|
SS$_NORMAL
|
The service completed successfully; proceed with the next erase step.
|
|
SS$_NOTRAN
|
The service completed successfully; security erase completed.
|
|
SS$_ACCVIO
|
The
patadr argument cannot be written by the caller.
|
|
SS$_BADPARAM
|
The
type argument or
count argument is invalid.
|
|
