TRYLOCK(D3) TRYLOCK(D3)
NAME
TRYLOCK - try to acquire a basic lock
SYNOPSIS
#include <sys/types.h>
#include <sys/ksynch.h>
#include <sys/ddi.h>
pl_t TRYLOCK(lock_t *lockp, pl_t pl);
Arguments
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.
DESCRIPTION
If the lock specified by lockp is immediately available (can
be acquired without waiting) TRYLOCK sets the interrupt
priority level in accordance with the value specified by pl
(if required by the implementation) and acquires the lock. If
the lock is not immediately available, the function returns
without acquiring the lock.
Return Values
If the lock is acquired, TRYLOCK returns the previous
interrupt priority level (plbase - plhi). If the lock is not
acquired the value invpl is returned.
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 to LOCK_ALLOC(D3) for additional
discussion and a list of the valid values for pl.
Implementations which do not require that the interrupt
priority level be raised during lock acquisition may choose to
ignore this argument.
TRYLOCK may be used to acquire a lock in a different order
from the order defined by the lock hierarchy.
When called from interrupt level, the pl argument must not
specify a priority level below the level at which the
interrupt handler is running.
Copyright 1994 Novell, Inc. Page 1
TRYLOCK(D3) TRYLOCK(D3)
Level
Base or Interrupt.
Synchronization Constraints
Does not sleep.
Driver-defined basic locks, read/write locks, and sleep locks
may be held across calls to this function.
REFERENCES
LOCK(D3), LOCK_ALLOC(D3), LOCK_DEALLOC(D3), UNLOCK(D3)
NOTICES
Portability
All processors
Applicability
ddi: 5, 5mp, 6, 6mp, 7, 7mp
Copyright 1994 Novell, Inc. Page 2