runtime: for kqueue treat EVFILT_READ with EV_EOF as permitting a write
On systems that use kqueue, we always register descriptors for both
EVFILT_READ and EVFILT_WRITE. On at least FreeBSD and OpenBSD, when
the write end of a pipe is registered for EVFILT_READ and EVFILT_WRITE
events, and the read end of the pipe is closed, kqueue reports an
EVFILT_READ event with EV_EOF set, but does not report an EVFILT_WRITE
event. Since the write to the pipe is waiting for an EVFILT_WRITE
event, closing the read end of a pipe can cause the write end to hang
rather than attempt another write which will fail with EPIPE.
Fix this by treating EVFILT_READ with EV_EOF set as making both reads
and writes ready to proceed.
The real test for this is in CL 71770, which tests using various
timeouts with pipes.
Updates #22114
Change-Id: Ib23fbaaddbccd8eee77bdf18f27a7f0aa50e2742
Reviewed-on: https://go-review.googlesource.com/71973
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
diff --git a/src/runtime/defs_dragonfly.go b/src/runtime/defs_dragonfly.go
index ed00be0..95014fe 100644
--- a/src/runtime/defs_dragonfly.go
+++ b/src/runtime/defs_dragonfly.go
@@ -103,6 +103,7 @@
EV_DELETE = C.EV_DELETE
EV_CLEAR = C.EV_CLEAR
EV_ERROR = C.EV_ERROR
+ EV_EOF = C.EV_EOF
EVFILT_READ = C.EVFILT_READ
EVFILT_WRITE = C.EVFILT_WRITE
)
