dg_lcntl(2) DG/UX 5.4.2 dg_lcntl(2)
NAME
dglcntl - process a record lock request on a filehandle
SYNOPSIS
#include <sys/fcntl.h>
#include <sys/nfs.h>
int dglcntl(cmd, fileptr, clientid, clientidinuseptr, flockptr)
int cmd;
fhandlet * fileptr;
int clientid;
int * clientidinuseptr;
struct flock * flockptr;
where:
cmd A lock command
fileptr An nfs file handle
clientid A client id for the lock
clientidinuseptr Whether lock client id is in use
flockptr Lock parameters
DESCRIPTION
Dglcntl processes the cmd lock request on the file given by the file
handle fileptr and lock client identifier clientid with the lock
parameters given in flockptr. Upon return, the value of
clientidinuseptr equals 1 if the clientid currently holds any
locks or lock requests, otherwise the value of clientidinuseptr
equals 0.
Dglcntl provides a variety of lock operations on file handles. It
is similar to fcntl(2), but takes a file handle argument rather than
a file descriptor, and a lock client identifier rather than using the
process id of the caller. A lock client id is a small integer
specified by the caller. Cmd is the lock command to be performed on
fileptr with clientid and flockptr specifying the lock parameters.
The flockptr parameters are treated the same as the fcntl(2) lock
parameters. On return, clientidinuseptr specifies whether
clientid holds any locks or pending lock requests. The commands
available are:
DG_LCNTL_SETLK Set or clear a file lock according to flockptr.
DG_LCNTL_SETLK is used to set read and write
locks, or remove either type of lock. If a read
or a write lock cannot be set, dglcntl returns
immediately with the value -1 and errno set to
EACCES. [See the fcntl(2) command F_SETLK.]
DG_LCNTL_SETLKD This command is the same as DG_LCNTL_SETLK except
if a read or write lock is blocked by other
locks, dglcntl queues a delayed lock request and
returns with the value -1, and errno set to
EINPROGRESS. The lock request is attempted when
the blocking lock is released. The results of
the delayed request are returned by the
Licensed material--property of copyright holder(s) 1
dg_lcntl(2) DG/UX 5.4.2 dg_lcntl(2)
dglockwait(2) call. If clientid already owns
a delayed lock request, then dglcntl returns -1
and errno is set to ENOLOCK.
DG_LCNTL_GETLK Get the first lock that blocks the lock
description specified by flockptr. The
information retrieved overwrites the information
passed to dglcntl in flockptr. If no lock is
found that would prevent this lock from being
set, then flockptr is unchanged, except for the
lock type, which is set to DG_LCNTL_UNLCK. [See
the fcntl(2) command F_GETLK.]
DG_LCNTL_CANCEL Remove the delayed lock request specified by
flockptr. If there is no delayed lock request,
then this command removes the lock specified by
flockptr. This is the only command that may be
issued for clientid while a delayed lock request
exists for clientid.
DG_LCNTL_RECLAIM Set or clear a file lock according to flockptr.
DG_LCNTL_RECLAIM is used during the system
restart grace period to reclaim read and write
locks. If a read or a write lock cannot be set,
dglcntl returns immediately with the value -1,
and errno is set to ENOLINK.
The only process that uses this function is the network lock server,
rpc.lockd.
ACCESS CONTROL
The caller must be super-user.
RETURN VALUE
0 The dglcntl operation was successful.
-1 An error occurred. errno indicates the error.
DIAGNOSTICS
Errno may be set to one of the following error codes regardless of
the value of cmd:
EPERM Must be super-user to use this system call.
EINVAL cmd is not one of the known values.
EACCES The cmd is DG_LCNTL_SETLK and the type of lock sought
is a read lock (DG_LCNTL_RDLCK) or write lock
(DG_LCNTL_WRLCK), and either the segment of a file to
be locked is already write-locked by another process,
or the type is a write lock and the segment of a file
to be locked is already read-locked or write-locked by
another process.
Licensed material--property of copyright holder(s) 2
dg_lcntl(2) DG/UX 5.4.2 dg_lcntl(2)
EFAULT One of the arguments points outside of the process's
readable address space.
ESTALE The filehandle specified in the request is no longer
valid.
EINTR The process received a signal while processing the
lock request.
EDEADLK The cmd is DG_LCNTL_SETLKW or DG_LCNTL_SETLKD and a
deadlock would exist if the lock were granted or
allowed to pend.
EINPROGRESS The cmd is DG_LCNTL_SETLKD and the lock request can
not be granted immediately, but has been queued for
later completion. When the lock currently blocking
the request is released, the request will be retried.
The results of the delayed request are returned by the
dglockwait(2) call.
ENOLCK The cmd can not be satisfied because there are no more
record locks available.
ENOLCK The cmd is DG_LCNTL_SETLKD and the clientid already
has a pending lock request.
ENOLCK The cmd is DG_LCNTL_RECLAIM but the lock specified by
flockptr can not be granted.
SEE ALSO
fcntl(2), dglockreset(2), dglockwait(2), lockf(3C), fcntl(5).
Licensed material--property of copyright holder(s) 3