[Help-smalltalk] [PATCH 5/5] libgst: Fix a race when polling on a filedescriptor

[Holger Hans Peter Freyther]

From: Paolo Bonzini <address@hidden>

It is possible that data arrives after the initial poll
and before enabling SIGIO/SIGPOLL of the filedescriptor.
This would lead to a read on a sockey being blocked forever
even when data is available.

2012-09-09  Paolo Bonzini  <address@hidden>

        * libgst/sysdep/posix/events.c: Register the fd with gst
        before polling.
---
 libgst/ChangeLog             |    5 +++++
 libgst/sysdep/posix/events.c |    5 ++++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/libgst/ChangeLog b/libgst/ChangeLog
index e04612c..31cd69a 100644
--- a/libgst/ChangeLog
+++ b/libgst/ChangeLog
@@ -1,3 +1,8 @@
+2012-09-09  Paolo Bonzini  <address@hidden>
+
+       * libgst/sysdep/posix/events.c: Register the fd with gst
+       before polling.
+
 2012-07-15  Paolo Bonzini  <address@hidden>
 
        * libgst/opt.c: Fix error in compute_jump_length that could lead
diff --git a/libgst/sysdep/posix/events.c b/libgst/sysdep/posix/events.c
index da3a784..2525b37 100644
--- a/libgst/sysdep/posix/events.c
+++ b/libgst/sysdep/posix/events.c
@@ -395,6 +395,10 @@ _gst_async_file_polling (int fd,
   polling_queue *new;
 
   index = num_used_pollfds++;
+
+  /* Enable async io on the fd before we poll as data could arrive after
+     the fd was polled and before the async io was enabled. */
+  set_file_interrupt (fd, file_polling_handler);
   result = _gst_sync_file_polling (fd, cond);
   if (result != 0)
     {
@@ -431,7 +435,6 @@ _gst_async_file_polling (int fd,
     }
   pollfds[index].revents = 0;
 
-  set_file_interrupt (fd, file_polling_handler);
 
   /* Even if I/O was made possible while setting up our machinery,
      the list will only be walked before the next bytecode, so there
-- 
1.7.10.4