PORT_ALERT(3C) Standard C Library Functions PORT_ALERT(3C)


NAME


port_alert - set a port in alert mode

SYNOPSIS


#include <port.h>

int port_alert(int port, int flags, int events, void *user);


DESCRIPTION


The port_alert() function transitions a port into or out of alert mode.
A port in alert mode immediately awakens all threads blocked in
port_get(3C) or port_getn(3C). These threads return with an alert
notification that consists of a single port_event_t structure with the
source PORT_SOURCE_ALERT. Subsequent threads trying to retrieve events
from a port that is in alert mode will return immediately with the alert
notification.


A port is transitioned into alert mode by calling the port_alert()
function with a non-zero events parameter. The specified events and user
parameters will be made available in the portev_events and the
portev_user members of the alert notification, respectively. The flags
argument determines the mode of operation of the alert mode:

o If flags is set to PORT_ALERT_SET, port_alert() sets the port
in alert mode independent of the current state of the port.
The portev_events and portev_user members are set or updated
accordingly.

o If flags is set to PORT_ALERT_UPDATE and the port is not in
alert mode, port_alert() transitions the port into alert mode.
The portev_events and portev_user members are set accordingly.

o If flags is set to PORT_ALERT_UPDATE and the port is already
in alert mode, port_alert() returns with an error value of
EBUSY.


PORT_ALERT_SET and PORT_ALERT_UPDATE are mutually exclusive.


A port is transitioned out of alert mode by calling the port_alert()
function with a zero events parameter.


Events can be queued to a port that is in alert mode, but they will not
be retrievable until the port is transitioned out of alert mode.

RETURN VALUES


Upon successful completion, 0 is returned. Otherwise, -1 is returned and
errno is set to indicate the error.

ERRORS


The port_alert() function will fail if:

EBADF
The port identifier is not valid.


EBADFD
The port argument is not an event port file descriptor.


EBUSY
The port is already in alert mode.


EINVAL
Mutually exclusive flags are set.


ATTRIBUTES


See attributes(5) for descriptions of the following attributes:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Architecture | all |
+--------------------+-----------------+
|Interface Stability | Evolving |
+--------------------+-----------------+
|MT-Level | Safe |
+--------------------+-----------------+

SEE ALSO


port_associate(3C), port_create(3C), port_get(3C), port_send(3C),
attributes(5)


April 9, 2016 PORT_ALERT(3C)