DAT_EVD_WAIT(3DAT)DAT_EVD_WAIT(3DAT)NAMEdat_evd_wait - remove first event from the Event Dispatcher event queue
cc [ flag... ] file... -ldat [ library... ]
IN DAT_EVD_HANDLE evd_handle,
IN DAT_TIMEOUT timeout,
IN DAT_COUNT threshold,
OUT DAT_EVENT *event,
OUT DAT_COUNT *nmore
Handle for an instance of the Event Dispatcher.
The duration of time, in microseconds, that the Consumer
is willing to wait for the event.
The number of events that should be on the EVD queue
before the operation should return with DAT_SUCCESS. The
threshold must be at least 1.
Pointer to the Consumer-allocated structure that the
Provider fills with the event data.
The snapshot of the queue size at the time of the opera‐
The dat_evd_wait() function removes the first event from the Event Dis‐
patcher event queue and fills the Consumer-allocated event structure
with event data. The first element in this structure provides the type
of the event; the rest provides the event type-specific parameters. The
Consumer should allocate an event structure big enough to hold any
event that the Event Dispatcher can deliver.
For all events, the Provider fills the dat_event that the Consumer
allocates. Therefore, for all events, all fields of dat_event are OUT
from the Consumer point of view. For DAT_CONNECTION_REQUEST_EVENT, the
Provider creates a Connection Request whose cr_handle is returned to
the Consumer in DAT_CR_ARRIVAL_EVENT_DATA. That object is destroyed by
the Provider as part of dat_cr_accept(3DAT), dat_cr_reject(3DAT), or
dat_cr_handoff(3DAT). The Consumer should not use cr_handle or any of
its parameters, including private_data, after one of these operations
destroys the Connection Request.
For DAT_CONNECTION_EVENT_ESTABLISHED for the Active side of connection
establishment, the Provider returns the pointer for private_data and
the private_data_size. For the Passive side, DAT_CONNEC‐
TION_EVENT_ESTABLISHED event private_data is not defined and pri‐
vate_data_size returns zero. The Provider is responsible for the memory
allocation and deallocation for private_data. The private_data is valid
until the Active side Consumer destroys the connected Endpoint
(dat_ep_free(3DAT)), or transitions the Endpoint into Unconnected state
so it is ready for the next connection. So, while the Endpoint is in
Connected, Disconnect Pending, or Disconnected state, the private_data
of DAT_CONNECTION_REQUEST_EVENT is still valid for Active side Con‐
Provider must pass to the Consumer the entire Private Data that the
remote Consumer provided for dat_ep_connect(3DAT), dat_ep_dup_con‐
nect(3DAT), and dat_cr_accept(). If the Consumer provides more data
than the Provider and Transport can support (larger than IA Attribute
of max_private_data_size), DAT_INVALID_PARAMETER is returned for that
A Consumer that blocks performing a dat_evd_wait() on an Event Dis‐
patcher effectively takes exclusive ownership of that Event Dispatcher.
Any other dequeue operation (dat_evd_wait() or dat_evd_dequeue(3DAT))
on the Event Dispatcher is rejected with a DAT_INVALID_STATE error
The CNO associated with the evd_handle() is not triggered upon event
arrival if there is a Consumer blocked on dat_evd_wait() on this Event
The timeout allows the Consumer to restrict the amount of time it is
blocked waiting for the event arrival. The value of DAT_TIMEOUT_INFI‐
NITE indicates that the Consumer waits indefinitely for an event
arrival. Consumers should use extreme caution in using this value.
When timeout value is reached and the number of events on the EVD queue
is below the threshold value, the operation fails and returns DAT_TIME‐
OUT_EXPIRED. In this case, no event is dequeued from the EVD and the
return value for the event argument is undefined. However, an nmore
value is returned that specifies the snapshot of the number of the
events on the EVD queue that is returned.
The threshold allows the Consumer to wait for a requested number of
event arrivals prior to waking the Consumer. If the value of the
threshold is larger than the Event Dispatcher queue length, the opera‐
tion fails with the return DAT_INVALID_PARAMETER. If a non-positive
value is specified for threshold, the operation fails and returns
If EVD is used by an Endpoint for a DTO completion stream that is con‐
figured for a Consumer-controlled event Notification (DAT_COMPLE‐
TION_UNSIGNALLED_FLAG or DAT_COMPLETION_SOLICITED_WAIT_FLAG for Receive
Completion Type for Receives; DAT_COMPLETION_UNSIGNALLED_FLAG for
Request Completion Type for Send, RDMA Read, RDMA Write and RMR Bind),
the threshold value must be 1. An attempt to specify some other value
for threshold for this case results in DAT_INVALID_STATE.
The returned value of nmore indicates the number of events left on the
Event Dispatcher queue after the dat_evd_wait() returns. If the opera‐
tion return value is DAT_SUCCESS, the nmore value is at least the value
of (threshold -1). Notice that nmore is only a snapshot and the number
of events can be changed by the time the Consumer tries to dequeue
events with dat_evd_wait() with timeout of zero or with
For returns other than DAT_SUCCESS, DAT_TIMEOUT_EXPIRED, and DAT_INTER‐
RUPTED_CALL, the returned value of nmore is undefined.
The returned event that was posted from an Event Stream guarantees Con‐
sumers that all events that were posted from the same Event Stream
prior to the returned event were already returned to a Consumer
directly through a dat_evd_dequeue() or dat_evd_wait() operation.
If the return value is neither DAT_SUCCESS nor DAT_TIMEOUT_EXPIRED,
then returned values of nmore and event are undefined. If the return
value is DAT_TIMEOUT_EXPIRED, then the return value of event is unde‐
fined, but the return value of nmore is defined. If the return value is
DAT_SUCCESS, then the return values of nmore and event are defined.
If this function is called on an EVD in an unwaitable state, or if
dat_evd_set_unwaitable(3DAT) is called on an EVD on which a thread is
blocked in this function, the function returns with DAT_INVALID_STATE.
The ordering of events dequeued by overlapping calls to dat_evd_wait()
or dat_evd_dequeue() is not specified.
The operation was successful. An event was
returned to a Consumer.
The evd_handle parameter is invalid.
The timeout or threshold parameter is invalid.
For example, threshold is larger than the
The operation was aborted because IA was
closed or EVD was destroyed
One of the parameters was invalid for this
operation. There is already a waiter on the
EVD, or the EVD is in an unwaitable state.
The operation timed out.
The operation was interrupted by a signal.
Consumers should be cautioned against using threshold combined with
Consumers should not mix different models for control of unblocking a
waiter. If the Consumer uses Notification Suppression or Solicited
Wait to control the Notification events for unblocking a waiter, the
threshold must be set to 1. If the Consumer uses threshold to control
when a waiter is unblocked, DAT_COMPLETION_UNSIGNALLED_FLAG locally and
DAT_COMPLETION_SOLICITED_WAIT remotely shall not be used. By default,
all completions are Notification events.
See attributes(5) for descriptions of the following attributes:
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
│Interface Stability │ Standard: uDAPL, 1.1, 1.2 │
│MT-Level │ Safe │
SEE ALSOdat_cr_accept(3DAT), dat_cr_handoff(3DAT), dat_cr_reject(3DAT),
dat_evd_dequeue(3DAT), dat_evd_set_unwaitable(3DAT), libdat(3LIB),
Jul 16, 2004 DAT_EVD_WAIT(3DAT)