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imc_lkacquire(3)
NAME
  imc_lkacquire - Acquires a lock from a lock set

LIBRARY
  Memory Channel API library (libimc.a)

SYNOPSIS
  #include <sys/imc.h>
  int imc_lkacquire (
	  imc_lkid_t lock,
	  int	     index,
	  int	     flag,
	  int	     trylock );

PARAMETERS
  lock	    Identifies the lock set from which the lock is to be acquired.
	    The lock set specified by the lock parameter must previously have
	    been allocated by a call to the imc_lkalloc() function.

  index	    Specifies the lock to be acquired. The value of the index
	    parameter is in the range zero (0) to (count-1), where count is
	    the value returned by the imc_lkalloc() function when it created
	    the lock set.

  flag	    This parameter is reserved for future use by Compaq. You must set
	    the value of this parameter to ZERO (0).

  trylock   Specifies whether the imc_lkacquire() function should return
	    immediately if the lock is busy or wait until it can acquire the
	    lock.  The trylock parameter contains one of the following
	    values:

	    IMC_LOCKWAIT
		      Wait until the lock becomes free and then acquire the
		      lock before returning.

	    IMC_LOCKNOWAIT
		      Return immediately if the lock is in use.

DESCRIPTION
  The imc_lkacquire() function tries to acquire the lock specified by the
  index parameter from the lock set specified in the lock parameter. If the
  lock is in use, the function can wait until the lock becomes free, or it
  can immediately return without acquiring the lock.  The return values for
  the function indicate whether the lock was successfully acquired.

  When a process acquires a lock, no other process executing on the cluster
  can acquire that lock.

  Waiting for busy locks to become free entails busy spinning, which has a
  significant effect on performance. Therefore, in the interest of overall
  system performance, applications should acquire locks only as they are
  needed and promptly release them.

  If a system failure occurs on a host on which a process that holds a lock
  is executing, all locks associated with the host are automatically
  released.

  All locks acquired by a process are automatically released when the process
  exits.

  It is illegal for a process to acquire locks recursively. If a process
  acquires a lock that it has already acquired and not released, an error
  will occur. The correct sequence is for the process to acquire the lock,
  release it, and then acquire it again.

RETURN VALUES
  The imc_lkacquire() function returns one of the following values:

  IMC_SUCCESS
	    Normal successful completion.

  IMC_BADLOCK
	    Either the lock set specified by the lock parameter or the lock
	    specified by the index parameter is out of range.

  IMC_BADPARM
	    An invalid parameter was specified in the call to the
	    imc_lkacquire function.

  IMC_CORRUPTLOCK
	    An attempt was made to acquire a lock from an invalid or
	    corrupted lock set.

  IMC_LOCKPRIOR
	    The process attempted to acquire a lock that it already holds.

  IMC_NOLOCKGOT
	    The imc_lkacquire() function returned without gaining ownership
	    of the lock.

RELATED INFORMATION
  Introduction: imc(3)

  Commands: imc_init(1), imcs(1)

  Functions: imc_api_init(3), imc_lkalloc(3), imc_lkdealloc(3),
  imc_lkrelease(3)

  Cluster Highly Available Applications

Index for Section 3

Alphabetical listing for I

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