PR-1129: Fix main loop timeout bug.

Calls to scheduler_check_fd_events return prematurely, failing to mark
a timeout pending, iff nfds is 0.

This leads to a condition where the deadline never gets reset, so the
next calculated timeout tv will be {0, 0} and we're left spinning in
select()s.

Fixed by separating fd and timeout checks.

Signed-off-by: Daniel Stodden <daniel.stodden@citrix.com>

diff --git a/drivers/scheduler.c b/drivers/scheduler.c
index 3274719ad22850edc4280e8a49dd1a7e8997aa18..43e13835c45b838f58300ed631a0164d5aa9e3e2 100644 (file)
--- a/drivers/scheduler.c
+++ b/drivers/scheduler.c
@@ -35,7 +35,7 @@
 #include "scheduler.h"
 #include "tapdisk-log.h"
 
-#define DBG(_f, _a...)               tlog_write(TLOG_DBG, _f, ##_a)
+#define DBG(_f, _a...)               if (0) { tlog_syslog(TLOG_DBG, _f, ##_a); }
 #define BUG_ON(_cond)                if (_cond) td_panic()
 
 #define SCHEDULER_MAX_TIMEOUT        600
@@ -117,17 +117,14 @@ scheduler_prepare_events(scheduler_t *s)
 }
 
 static int
-scheduler_check_events(scheduler_t *s, int nfds)
+scheduler_check_fd_events(scheduler_t *s, int nfds)
 {
        event_t *event;
-       struct timeval now;
-
-       if (nfds <= 0)
-               return nfds;
-
-       gettimeofday(&now, NULL);
 
        scheduler_for_each_event(s, event) {
+               if (!nfds)
+                       break;
+
                if (event->dead)
                        continue;
 
@@ -151,16 +148,45 @@ scheduler_check_events(scheduler_t *s, int nfds)
                        event->pending |= SCHEDULER_POLL_EXCEPT_FD;
                        --nfds;
                }
+       }
+
+       return nfds;
+}
+
+static void
+scheduler_check_timeouts(scheduler_t *s)
+{
+       struct timeval now;
+       event_t *event;
+
+       gettimeofday(&now, NULL);
+
+       scheduler_for_each_event(s, event) {
+               BUG_ON(event->pending && event->masked);
 
-               if (event->pending) {
-                       BUG_ON(event->masked);
+               if (event->dead)
+                       continue;
+
+               if (event->pending)
+                       continue;
+
+               if (!(event->mode & SCHEDULER_POLL_TIMEOUT))
                        continue;
-               }
 
-               if ((event->mode & SCHEDULER_POLL_TIMEOUT) &&
-                   (event->deadline <= now.tv_sec))
-                       event->pending = SCHEDULER_POLL_TIMEOUT;
+               if (event->deadline > now.tv_sec)
+                       continue;
+
+               event->pending = SCHEDULER_POLL_TIMEOUT;
        }
+}
+
+static int
+scheduler_check_events(scheduler_t *s, int nfds)
+{
+       if (nfds)
+               nfds = scheduler_check_fd_events(s, nfds);
+
+       scheduler_check_timeouts(s);
 
        return nfds;
 }