From 39ebef82aae86976fc5e1bc293bcb677a064d3ee Mon Sep 17 00:00:00 2001
From: Willy Tarreau <w@1wt.eu>
Date: Fri, 14 Dec 2012 00:17:03 +0100
Subject: [PATCH] BUG/MINOR: poll: the I/O handler was called twice for polled
 I/Os

When a polled I/O event is detected, the event is added to the updates
list and the I/O handler is called. Upon return, if the event handler
did not experience an EAGAIN, the event remains in the updates list so
that it will be processed later. But if the event was already in the
spec list, its state is updated and it will be called again immediately
upon exit, by fd_process_spec_events(), so this creates unfairness
between speculative events and polled events.

So don't call the I/O handler upon I/O detection when the FD already is
in the spec list. The fd events are still updated so that the spec list
is up to date with the possible I/O change.
---
 src/ev_epoll.c  | 5 +++++
 src/ev_kqueue.c | 7 +++++++
 src/ev_poll.c   | 7 +++++++
 src/ev_select.c | 7 +++++++
 4 files changed, 26 insertions(+)

diff --git a/src/ev_epoll.c b/src/ev_epoll.c
index 5f7b7c3d7..90efaee05 100644
--- a/src/ev_epoll.c
+++ b/src/ev_epoll.c
@@ -179,6 +179,11 @@ REGPRM2 static void _do_poll(struct poller *p, int exp)
 			if (fdtab[fd].ev & FD_POLL_OUT)
 				fd_ev_set(fd, DIR_WR);
 
+			if (fdtab[fd].spec_p) {
+				/* This fd was already scheduled for being called as a speculative I/O */
+				continue;
+			}
+
 			/* Save number of updates to detect creation of new FDs. */
 			old_updt = fd_nbupdt;
 			fdtab[fd].iocb(fd);
diff --git a/src/ev_kqueue.c b/src/ev_kqueue.c
index 36a7b7f41..2142132e2 100644
--- a/src/ev_kqueue.c
+++ b/src/ev_kqueue.c
@@ -158,6 +158,13 @@ REGPRM2 static void _do_poll(struct poller *p, int exp)
 			if (fdtab[fd].ev & FD_POLL_OUT)
 				fd_ev_set(fd, DIR_WR);
 
+			if (fdtab[fd].spec_p) {
+				/* This fd was already scheduled for being
+				 * called as a speculative I/O.
+				 */
+				continue;
+			}
+
 			fdtab[fd].iocb(fd);
 		}
 	}
diff --git a/src/ev_poll.c b/src/ev_poll.c
index c09232e4b..e3ea4db63 100644
--- a/src/ev_poll.c
+++ b/src/ev_poll.c
@@ -181,6 +181,13 @@ REGPRM2 static void _do_poll(struct poller *p, int exp)
 			if (fdtab[fd].ev & FD_POLL_OUT)
 				fd_ev_set(fd, DIR_WR);
 
+			if (fdtab[fd].spec_p) {
+				/* This fd was already scheduled for being
+				 * called as a speculative I/O
+				 */
+				continue;
+			}
+
 			fdtab[fd].iocb(fd);
 		}
 	}
diff --git a/src/ev_select.c b/src/ev_select.c
index 48a62da18..dba5928c3 100644
--- a/src/ev_select.c
+++ b/src/ev_select.c
@@ -167,6 +167,13 @@ REGPRM2 static void _do_poll(struct poller *p, int exp)
 				if (fdtab[fd].ev & FD_POLL_OUT)
 					fd_ev_set(fd, DIR_WR);
 
+				if (fdtab[fd].spec_p) {
+					/* This fd was already scheduled for being
+					 * called as a speculative I/O.
+					 */
+					continue;
+				}
+
 				fdtab[fd].iocb(fd);
 			}
 		}