Specifications

Operating System Routines

SMP$RESTORE

Releases a single acquisition of a fork lock or spinlock held by the local processor.

Module

SPINLOCKS

Macro

FORKUNLOCK, UNLOCK

Input

Location Contents

R0 Fork lock or spinlock index

Output

Location Contents

R0 Fork lock or spinlock index

Synchronization

Upon entry, the local processor must be executing at or above the IPL at which

the lock was originally obtained. This IPL must be greater than IPL$_ASTDEL.

Violations of IPL synchronization in a full-checking multiprocessing environment

result in a SPLIPLLOW bugcheck. At exit, IPL is unchanged and the lock may or

may not be still held.

Description

The FORKUNLOCK and UNLOCK macros call SMP$RESTORE when RESTORE

is speciﬁed as the condition argument.

SMP$RESTORE ﬁrst veriﬁes that the local processor owns the speciﬁed lock. If

this is not the case, the procedure issues an SPLRSTERR bugcheck. Otherwise,

SMP$RESTORE proceeds to decrement the ownership count of the lock. If the

ownership count of the lock drops to its initial state, the procedure releases the

lock and makes it available to other processors.

3–155