Description
Use the SETLOCK macro to control access to serially reusable resources. Each kind of serially reusable resource is assigned a separate lock.
SETLOCK can do the following:
- Obtain a specified lock
- Release a specified lock
- Test a specified lock or determine if the lock is held on the caller's processor.
Locks are discussed in the “Serialization” chapter in z/OS MVS Programming: Authorized Assembler Services Guide.
Note: The OBTAIN, RELEASE, and TEST options of the SETLOCK macro have
the same environmental specifications, programming requirements, restrictions,
register information, and performance implications described below,
except where noted in the explanations of each option.
Environment
The requirements for the caller are:
| Environmental factor | Requirement |
|---|---|
| Minimum authorization: | Supervisor state, PSW key 0 |
| Dispatchable unit mode: | Task or SRB |
| Cross memory mode: | Any |
| AMODE: | 24- or 31-bit |
| ASC mode: | Primary or access register (AR) |
| Interrupt status: | Enabled or disabled for I/O and external interrupts. The caller cannot be disabled when unconditionally requesting a suspend lock. |
| Locks: | LOCAL or CML lock must be held to obtain the CMS lock; otherwise, the caller may hold locks, but is not required to hold any. Only locks lower in the hierarchy than the lock currently being requested may be held at the time of invocation. |
| Control parameters: | None. |
Programming requirements
- Before you invoke the SETLOCK macro in access register mode, issue SYSSTATE ASCENV=AR.
- The caller must include the IHAPSA mapping macro.
- Before issuing an OBTAIN request for a CML lock, establish the target ASCB as either the primary or secondary address space.
Restrictions
None.
Input register information
Before issuing the SETLOCK macro, the caller must ensure that the
following general purpose register (GPR) contains the specified information:
- Register
- Contents
- 13
- A 5-word save area if REGS=SAVE is specified, or an 18-word save area if REGS=STDSAVE is specified.
Output register information
For an OBTAIN or RELEASE request, when the REGS parameter is not
specified, the contents of the general purpose registers (GPRs) after
control returns to the caller are as follows:
- Register
- Contents
- 0-10
- Unchanged
- 11-12
- Used as work registers by the system
- 13
- Return code
- 14
- Used as a work register by the system
- 15
- Unchanged
For an OBTAIN or RELEASE request when the REGS parameter is specified, see the description of the REGS parameter for information on GPR usage.
For a TEST request, the contents of the GPRs after control returns
to the caller are as follows:
- Register
- Contents
- 0-1
- Unchanged.
- 2-12
- If one of these registers is specified on the LOCKHLD parameter, that register is used as a work register by the system; otherwise, registers 2-12 are unchanged.
- 13-14
- Unchanged.
When control returns to the caller, the access registers (ARs)
contain:
- Register
- Contents
- 0-1
- Used as work registers by the system
- 2-13
- Unchanged
- 14-15
- Used as work registers by the system
Some callers depend on register contents remaining the same before and after issuing a service. If the system changes the contents of registers on which the caller depends, the caller must save them before issuing the service, and restore them after the system returns control.
Performance implications
None.