SIGEVENT(7) Linux Programmer's Manual SIGEVENT(7)


sigevent - structure for notification from asynchronous routines


union sigval { /* Data passed with notification */
int sival_int; /* Integer value */
void *sival_ptr; /* Pointer value */

struct sigevent {
int sigev_notify; /* Notification method */
int sigev_signo; /* Notification signal */
union sigval sigev_value; /* Data passed with
notification */
void (*sigev_notify_function) (union sigval);
/* Function used for thread
notification (SIGEV_THREAD) */
void *sigev_notify_attributes;
/* Attributes for notification thread
pid_t sigev_notify_thread_id;
/* ID of thread to signal (SIGEV_THREAD_ID) */


The sigevent structure is used by various APIs to describe the way a process is to be notified about an event (e.g., completion of an asynchronous request, expiration of a timer, or the arrival of a message).

The definition shown in the SYNOPSIS is approximate: some of the fields in the sigevent structure may be defined as part of a union. Programs should employ only those fields relevant to the value specified in sigev_notify.

The sigev_notify field specifies how notification is to be performed. This field can have one of the following values:

A "null" notification: don't do anything when the event occurs.
Notify the process by sending the signal specified in sigev_signo.
If the signal is caught with a signal handler that was registered using the sigaction(2) SA_SIGINFO flag, then the following fields are set in the siginfo_t structure that is passed as the second argument of the handler:
This field is set to a value that depends on the API delivering the notification.
This field is set to the signal number (i.e., the same value as in sigev_signo).
This field is set to the value specified in sigev_value.
Depending on the API, other fields may also be set in the siginfo_t structure.
The same information is also available if the signal is accepted using sigwaitinfo(2).
Notify the process by invoking sigev_notify_function "as if" it were the start function of a new thread. (Among the implementation possibilities here are that each timer notification could result in the creation of a new thread, or that a single thread is created to receive all notifications.) The function is invoked with sigev_value as its sole argument. If sigev_notify_attributes is not NULL, it should point to a pthread_attr_t structure that defines attributes for the new thread (see pthread_attr_init(3)).
SIGEV_THREAD_ID (Linux-specific)
Currently used only by POSIX timers; see timer_create(2).




timer_create(2), aio_fsync(3), aio_read(3), aio_write(3), getaddrinfo_a(3), lio_listio(3), mq_notify(3), aio(7), pthreads(7)


This page is part of release 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.
2011-09-09 GNU