Copyright (c) 2016 John H. Baldwin <jhb@FreeBSD.org>
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$FreeBSD: stable/11/share/man/man3/sigevent.3 367457 2020-11-07 18:10:59Z dim $
.Dd July 15, 2016 .Dt SIGEVENT 3 .Os .Sh NAME .Nm sigevent .Nd "asynchronous event notification" .Sh SYNOPSIS n signal.h .Sh DESCRIPTION Some operations permit threads to request asychronous notification of events via a .Vt struct sigevent structure. This structure contains several fields that describe the requested notification: l -column ".Vt void (*)(union sigval)" ".Va sigev_notify_kevent_flags" t Sy Type Ta Sy Member Ta Sy Description t Vt int Ta sigev_notify Ta notification method t Vt int Ta sigev_signo Ta signal number t Vt union sigval Ta sigev_value Ta signal value t Vt int Ta sigev_notify_kqueue Ta .Xr kqueue 2 file descriptor t Vt unsigned short Ta sigev_notify_kevent_flags Ta kevent flags t Vt lwpid_t Ta sigev_notify_thread_id Ta LWP ID t Vt void (*)(union sigval) Ta sigev_notify_function Ta callback function pointer t Vt pthread_attr_t * Ta sigev_notify_attributes Ta callback thread attributes .El
p The .Va sigev_notify field specifies the notification method used when the event triggers: l -tag -width ".Dv SIGEV_THREAD_ID" t Dv SIGEV_NONE No notification is sent. t Dv SIGEV_SIGNAL The signal .Va sigev_signo is queued as a real-time signal to the calling process. The value stored in .Va sigev_value will be present in the .Va si_value of the .Vt siginfo_t structure of the queued signal. t Dv SIGEV_THREAD The notification function in .Va sigev_notify_function is called in a separate thread context. The thread is created with the attributes specified in .Va *sigev_notify_attributes . The value stored in .Va sigev_value is passed as the sole argument to .Va sigev_notify_function . If .Va sigev_notify_attributes is .Dv NULL , the thread is created with default attributes. t Dv SIGEV_KEVENT A new kevent is posted to the kqueue .Va sigev_notify_kqueue . The .Va udata member of the kevent structure contains the value stored in .Va sigev_value . The meaning of other fields in the kevent are specific to the type of triggered event. t Dv SIGEV_THREAD_ID The signal .Va sigev_signo is queued to the thread whose LWP ID is .Va sigev_notify_thread_id . The value stored in .Va sigev_value will be present in the .Va si_value of the .Vt siginfo_t structure of the queued signal. .El .Sh NOTES Note that programs wishing to use .Dv SIGEV_THREAD notifications must link against the .Lb librt . .Sh SEE ALSO .Xr aio_read 2 , .Xr mq_notify 2 , .Xr timer_create 2 , .Xr siginfo 3 .Sh STANDARDS The .Vt struct sigevent type conforms to .St -p1003.1-2004 .