Add patch to fix wine deadlock, bug #436780.

(Portage version: 2.2.0_alpha134/cvs/Linux x86_64)

1 files changed, 46 insertions, 0 deletions

diff --git a/x11-libs/libxcb/files/libxcb-1.8.1-multithread-deadlock.patch b/x11-libs/libxcb/files/libxcb-1.8.1-multithread-deadlock.patch
new file mode 100644
index 000000000000..d09b24dbe88f
--- /dev/null
+++ b/x11-libs/libxcb/files/libxcb-1.8.1-multithread-deadlock.patch
@@ -0,0 +1,46 @@
+From 23911a707b8845bff52cd7853fc5d59fb0823cef Mon Sep 17 00:00:00 2001
+From: Uli Schlachter <psychon@znc.in>
+Date: Mon, 24 Sep 2012 20:07:51 +0000
+Subject: Fix a multi-thread deadlock
+
+This fixes a deadlock which was seen in-the-wild with wine.
+
+It could happen that two threads tried to read from the socket at the same time
+and one of the thread got stuck inside of poll()/select().
+
+The fix works by making sure that the writing thread doesn't steal the reading
+thread's reply.
+
+Debugged-by: Erich Hoover <ehoover@mines.edu>
+Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=54671
+Signed-off-by: Uli Schlachter <psychon@znc.in>
+---
+diff --git a/src/xcb_conn.c b/src/xcb_conn.c
+index e01d566..6a7a806 100644
+--- a/src/xcb_conn.c
++++ b/src/xcb_conn.c
+@@ -432,10 +432,20 @@ int _xcb_conn_wait(xcb_connection_t *c, pthread_cond_t *cond, struct iovec **vec
+ 
+     if(ret)
+     {
++        /* The code allows two threads to call select()/poll() at the same time.
++         * First thread just wants to read, a second thread wants to write, too.
++         * We have to make sure that we don't steal the reading thread's reply
++         * and let it get stuck in select()/poll().
++         * So a thread may read if either:
++         * - There is no other thread that wants to read (the above situation
++         *   did not occur).
++         * - It is the reading thread (above situation occurred).
++         */
++        int may_read = c->in.reading == 1 || !count;
+ #if USE_POLL
+-        if((fd.revents & POLLIN) == POLLIN)
++        if(may_read && (fd.revents & POLLIN) == POLLIN)
+ #else
+-        if(FD_ISSET(c->fd, &rfds))
++        if(may_read && FD_ISSET(c->fd, &rfds))
+ #endif
+             ret = ret && _xcb_in_read(c);
+ 
+--
+cgit v0.9.0.2-2-gbebe