From: Willy Tarreau <w@1wt.eu>
Date: Thu, 13 Dec 2012 23:17:03 +0000 (+0100)
Subject: BUG/MINOR: poll: the I/O handler was called twice for polled I/Os
X-Git-Tag: v1.5-dev16~34
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=39ebef82aae86976fc5e1bc293bcb677a064d3ee;p=thirdparty%2Fhaproxy.git

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.
---

diff --git a/src/ev_epoll.c b/src/ev_epoll.c
index 5f7b7c3d7b..90efaee054 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 36a7b7f41f..2142132e21 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 c09232e4b9..e3ea4db63c 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 48a62da18a..dba5928c36 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);
 			}
 		}