Attachment 44414 Details for Bug 20708 – Proposed patch which fixes Reinhard Nißl's test case for me

[patch] Proposed patch which fixes Reinhard Nißl's test case for me

0001-Fix-deadlock-in-_XReply.patch (text/plain), 1.58 KB, created by Uli Schlachter on 2011-03-13 07:00:23 UTC

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Creator: Uli Schlachter

Created: 2011-03-13 07:00:23 UTC

Size: 1.58 KB

patch

obsolete

>From 829da0516bd81bd548abec2927e8f538cf5b5629 Mon Sep 17 00:00:00 2001
>From: Uli Schlachter <psychon@znc.in>
>Date: Sun, 13 Mar 2011 14:53:31 +0100
>Subject: [PATCH] Fix deadlock in _XReply
>
>_XReply waited for user locks from other thread. However, if the other thread is
>in _XReply, too, it might be waiting for this thread to handle the current
>reply.
>
>Since this code already had the internal dock prior to the UnlockDisplay() two
>lines prior to the InternalLockDisplay() in question, it doesn't make sense to
>wait for user locks anyway. Ignoring those makes the deadlock go away.
>
>Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=20708
>
>Signed-off-by: Uli Schlachter <psychon@znc.in>
>---
> src/xcb_io.c |    7 ++++++-
> 1 files changed, 6 insertions(+), 1 deletions(-)
>
>diff --git a/src/xcb_io.c b/src/xcb_io.c
>index 7e685de..75f16ef 100644
>--- a/src/xcb_io.c
>+++ b/src/xcb_io.c
>@@ -531,7 +531,12 @@ Status _XReply(Display *dpy, xReply *rep, int extra, Bool discard)
> 		req->reply_waiter = 1;
> 		UnlockDisplay(dpy);
> 		response = xcb_wait_for_reply(c, req->sequence, &error);
>-		InternalLockDisplay(dpy, /* don't skip user locks */ 0);
>+		/* This skips user locks, because we already had the lock before
>+		 * the UnlockDisplay() above, so we don't care if some other
>+		 * threads has a user lock. (The thread with the user lock
>+		 * might be in the ConditionWait() above waiting for us to handle
>+		 * this reply!) */
>+		InternalLockDisplay(dpy, /* do skip user locks */ 1);
> 
> 		/* We have the response we're looking for. Now, before
> 		 * letting anyone else process this sequence number, we
>-- 
>1.7.2.3
>

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Attachments on bug 20708: 23963 | 44413 | 44414 | 44621

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