SVR5

LOCK(D3)

LOCK -- acquire a basic lock

Synopsis

   #include <sys/types.h>
   #include <sys/ksynch.h>
   #include <sys/ddi.h>
   
   pl_t LOCK(lock_t *lockp, pl_t pl);

Arguments

Description

LOCK sets the interrupt priority level in accordance with the value specified by pl (if required by the implementation) and acquires the lock specified by lockp. If the lock is not immediately available, the caller will wait until the lock is available. It is implementation defined whether the caller will block during the wait. Some implementations may cause the caller to spin for the duration of the wait, while on others the caller may block at some point.

lockp: Pointer to the basic lock to be acquired.
pl: The interrupt priority level to be set while the lock is held by the caller.

Return values

Upon acquiring the lock, LOCK returns the previous interrupt priority level (plbase - plhi).

Usage

Because some implementations require that interrupts that might attempt to acquire the lock be blocked on the processor on which the lock is held, portable drivers must specify a pl value that is sufficient to block out any interrupt handler that might attempt to acquire this lock. See the description of the ``min_pl'' argument on the pl(D5) manual page for additional discussion and a list of the valid values for pl. Implementations that do not require that the interrupt priority level be raised during lock acquisition may ignore this argument.

Context and synchronization

Non-blockable, interrupt, user, or blockable context.

Basic locks are not recursive. A call to LOCK attempting to acquire a lock that is currently held by the calling context will result in deadlock.

Calls to LOCK should honor the ordering defined by the lock hierarchy(D5) in order to avoid deadlock.

When called from interrupt level, the pl argument must not specify a priority level below the level at which the interrupt handler is running.

Hardware applicability

All

Version applicability

ddi: 5, 5mp, 6, 6mp, 7, 7mp, 7.1, 7.1mp, 8, 8mp

References

LOCK_ALLOC(D3), LOCK_DEALLOC(D3), pl(D5), TRYLOCK(D3), UNLOCK(D3)

``Spin locks (DDI)'' in HDK Technical Reference