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imc_lkalloc(3)
NAME
  imc_lkalloc - Creates a lock set

LIBRARY
  Memory Channel API library (libimc.a)

SYNOPSIS
  #include <sys/imc.h>
  int imc_lkalloc (
	  imc_key_t  key,
	  int	     *count,
	  imc_perm_t perm,
	  int	     flag,
	  imc_lkid_t *lock );

PARAMETERS
  key	    Identifies the lock set to be allocated.

  count	    Specifies the number of locks created in the lock set, and
	    returns the number of locks actually created.

  perm	    Specifies the access permission for the lock set. The permission
	    code is similar to the UNIX permission convention, except that
	    there is no execute flag. The value of the perm parameter is
	    obtained by carrying out a logical OR operation on the following
	    values:

	    IMC_LKU   User access to locks

	    IMC_LKG   Group access to locks

	    IMC_LKO   Other access to locks

  flag	    Specifies the creation flag for the lock set. The flag parameter
	    has one of the following values:

	    IMC_CREATOR
		      If the lock set does not already exist on the cluster,
		      allocate the lock set and atomically acquire the first
		      lock (that is, lock zero (0)) in the set.	 If the
		      IMC_CREATOR flag is specified for a lock set that
		      already exists, an error condition will result.

	    NULL      Allocate the lock set without attempting to acquire the
		      first lock in the set.

  lock	    Returns a value that uniquely identifies the allocated lock set.
	    If the imc_lkalloc function fails to allocate a lock set, the
	    value of the lock parameter is undefined.

DESCRIPTION
  The imc_lkalloc() function creates a set of locks that enable applications
  to coordinate access to clusterwide resources. The number of locks in the
  lock set is specified by the count parameter.	 The maximum number of locks
  that a set can contain is specified by the IMC_MAXNUMLOCKS value in the
  Memory Channel API library header file.

  The imc_lkalloc() function provides a feature that allows a process to
  atomically (that is, in a single operation) allocate a lock set and acquire
  the first lock in the set. You can use this feature to coordinate
  application initialization in a cluster. To atomically allocate the lock
  set and acquire the first lock, specify the value IMC_CREATOR for the flag
  parameter.

  The method for establishing a relationship between a lock and a resource is
  application-specific, and is beyond the scope of the Memory Channel API
  library.

  All lock sets allocated by a process are automatically deallocated when the
  process exits.

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

  IMC_SUCCESS
	    Normal successful completion.

  IMC_BADPARM
	    An invalid parameter was specified in the call to the
	    imc_lkalloc() function.

  IMC_BADSIZE
	    The lock set is already allocated on the cluster, and the size of
	    the set as specified in this call to the imc_lkalloc() function
	    does not match the size specified in the previous call.

  IMC_EXISTS
	    The lock set already exists on the cluster.

  IMC_MAPENTRIES
	    An attempt has been made to exceed the maximum number of process
	    map entries. This maximum is set by the vm-mapentries parameter.

  IMC_MCFULL
	    There is not enough Memory Channel address space available to
	    allocate the lock set.

  IMC_NOMEM There is insufficient local memory available to allocate the lock
	    set.

  IMC_NORESOURCES
	    There are insufficient Memory Channel data structures available
	    to allocate the lock set.

  IMC_NOTINIT
	    This host has not been initialized to use the Memory Channel
	    Application Programming Interface (API) library.

  IMC_PERMIT
	    The lock set is already allocated, with a permission code that is
	    incompatible with the code specified in the perm parameter.

  IMC_PRIOR The lock set has already been allocated by the calling process.

RELATED INFORMATION
  Introduction: imc(3)

  Commands: imc_init(1), imcs(1)

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

  Cluster Highly Available Applications

Index for Section 3

Alphabetical listing for I

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