If multiple threads call kevent() to get AIO events on same kqueue fd,

it is possible that a single AIO event will be reported to multiple
threads, it is not threading friendly, and the existing API can not
control this behavior.
Allocate a kevent flags field sigev_notify_kevent_flags for AIO event
notification in sigevent, and allow user to pass EV_CLEAR, EV_DISPATCH
or EV_ONESHOT to AIO kernel code, user can control whether the event
should be cleared once it is retrieved by a thread. This change should
be comptaible with existing application, because the field should have
already been zero-filled, and no additional action will be taken by
kernel.

PR:	kern/156567

1 files changed, 2 insertions, 0 deletions

diff --git a/sys/sys/signal.h b/sys/sys/signal.h
index 971683516e3c..73aeea117f7d 100644
--- a/sys/sys/signal.h
+++ b/sys/sys/signal.h
@@ -169,12 +169,14 @@ struct sigevent {
 			void (*_function)(union sigval);
 			void *_attribute; /* pthread_attr_t * */
 		} _sigev_thread;
+		unsigned short _kevent_flags;
 		long __spare__[8];
 	} _sigev_un;
 };
 
 #if __BSD_VISIBLE
 #define	sigev_notify_kqueue		sigev_signo
+#define	sigev_notify_kevent_flags	_sigev_un._kevent_flags
 #define	sigev_notify_thread_id		_sigev_un._threadid
 #endif
 #define	sigev_notify_function		_sigev_un._sigev_thread._function