iofunc_lock()

Lock a resource

Synopsis:

#include <sys/iofunc.h>

int iofunc_lock( resmgr_context_t * ctp,
                 io_lock_t * msg,
                 iofunc_ocb_t * ocb,
                 iofunc_attr_t * attr );

Arguments:

ctp

A pointer to a resmgr_context_t structure that the resource-manager library uses to pass context information between functions.

msg

A pointer to the io_lock_t structure that contains the message that the resource manager received.

ocb

A pointer to the iofunc_ocb_t structure for the Open Control Block that was created when the client opened the resource.

attr

A pointer to the iofunc_attr_t structure that describes the characteristics of the device that's associated with your resource manager.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The function iofunc_lock() does what is required for POSIX locks. For more information, see lockf().

Returns:

EACCES or EAGAIN

The operation is F_TLOCK or F_TEST, and the section is already locked by another process.

EAGAIN

The operation is F_LOCK or F_TLOCK, and the file is mapped with mmap().

EBADF

The file descripter isn't valid, or the operation is F_LOCK or F_TLOCK, and the file descriptor isn't open for writing.

EDEADLK

The operation is F_LOCK, and a deadlock was detected.

EINTR

A signal was caught during execution of the function.

EINVAL

The operation isn't one of F_LOCK, F_TLOCK, F_TEST, or F_ULOCK, or the size plus the current file offset is less than 0.

ENOMEM

The system can't allocate sufficient memory to store lock resources.

EOPNOTSUPP or EINVAL

The implementation doesn't support the locking of files of the type indicated by the file descriptor.

EOVERFLOW

The offset of the first, or if the size isn't 0 then the last, byte in the requested section can't be represented correctly in an object of type off_t.

Classification:

QNX Neutrino

See also:

iofunc_lock_calloc(), iofunc_lock_free(), lockf()

Writing a Resource Manager

Resource Managers chapter of Getting Started with QNX Neutrino