Don't use EV_CLEAR for kqueue events.

For the semantics to match the epoll implementation, we need a socket to
continue to appear readable/writable if you wait multiple times without
doing I/O in between (in Linux terminology: level-triggered rather than
edge-triggered).  This distinction will be important for later commits.
Similar to commit 3b790d256f8 for Windows.

Reviewed-by: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Discussion: https://postgr.es/m/CA%2BhUKGJAC4Oqao%3DqforhNey20J8CiG2R%3DoBPqvfR0vOJrFysGw%40mail.gmail.com

diff --git a/src/backend/storage/ipc/latch.c b/src/backend/storage/ipc/latch.c
index d4c6c65baa3db01e1a711d0eeda6349f47f2ce9c..e2f4b116b9bb6d048fc009ba7b511b4189a3d3a0 100644 (file)
--- a/src/backend/storage/ipc/latch.c
+++ b/src/backend/storage/ipc/latch.c
@@ -991,7 +991,7 @@ WaitEventAdjustKqueueAdd(struct kevent *k_ev, int filter, int action,
 {
        k_ev->ident = event->fd;
        k_ev->filter = filter;
-       k_ev->flags = action | EV_CLEAR;
+       k_ev->flags = action;
        k_ev->fflags = 0;
        k_ev->data = 0;
        AccessWaitEvent(k_ev) = event;
@@ -1003,7 +1003,7 @@ WaitEventAdjustKqueueAddPostmaster(struct kevent *k_ev, WaitEvent *event)
        /* For now postmaster death can only be added, not removed. */
        k_ev->ident = PostmasterPid;
        k_ev->filter = EVFILT_PROC;
-       k_ev->flags = EV_ADD | EV_CLEAR;
+       k_ev->flags = EV_ADD;
        k_ev->fflags = NOTE_EXIT;
        k_ev->data = 0;
        AccessWaitEvent(k_ev) = event;