iofunc_lock_default()
Default handler for _IO_LOCK messages
Synopsis:
#include <sys/iofunc.h>
int iofunc_lock_default( resmgr_context_t * ctp,
io_lock_t * msg,
iofunc_ocb_t * ocb );
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; see iofunc_lock().
- ocb
- A pointer to the iofunc_ocb_t structure for the Open Control Block that was created when the client opened the resource.
Library:
libc
Use the -l c option to qcc to link against this library. This library is usually included automatically.
Description:
The iofunc_lock_default() function implements POSIX semantics for the _IO_LOCK message (generated as a result of a client fcntl() call).
You can place this function directly into the resmgr_io_funcs_t table passed as the io_funcs argument to resmgr_attach(), at the lock position, or you can call iofunc_func_init() to initialize all of the functions to their default values.
The iofunc_lock_default() function verifies that the client has the necessary permissions to effect a lock on the resource. This includes checking for read and write permissions against the type of lock being effected. If so, the lock is performed, modifying elements of the ocb->attr structure, and updating ocb->attr->locklist to reflect the new lock. This function calls iofunc_lock() to do the actual work.
Returns:
- -1
- Success; the resource manager library should return a one-part IOV to the client.
- EINVAL
- An invalid range was specified for the lock operation, or an invalid lock operation was attempted.
- EBADF
- An attempt to perform a read lock on a write-only resource, or a write lock on a read-only resource was attempted.
- ENOMEM
- Insufficient memory exists to allocate an internal lock structure.
Classification:
| Safety: | |
|---|---|
| Cancellation point | No |
| Signal handler | Yes |
| Thread | Yes |