Mercurial > sdl-ios-xcode
annotate sdl-config.in @ 4105:84882a89ca50 SDL-1.2
Date: Thu, 27 Dec 2007 07:38:25 +0000
From: John Bartholomew
Subject: [SDL] SDL Semaphore implementation broken on Windows?
Hi,
Over the past couple of days, I've been battling with SDL, SDL_Mixer and SMPEG to try to find an audio hang bug. I believe I've found the problem, which I think is a race condition inside SDL's semaphore implementation (at least the Windows implementation). The semaphore code uses Windows' built in semaphore functions, but it also maintains a separate count value. This count value is updated with bare increment and decrement operations in SemPost and SemWaitTimeout - no locking primitives to protect them.
In tracking down the apparent audio bug, I found that at some point a semaphore's count value was being decremented to -1, which is clearly not a valid value for it to take.
I'm still not certain exactly what sequence of operations is occuring for this to happen, but I believe that overall it's a race condition between a thread calling SemPost (which increments the count) and the thread on the other end calling SemWait (which decrements it).
I will try to make a test case to verify this, but I'm not sure if I'll be able to (threading errors being difficult to reproduce even in the best circumstances).
However, assuming this is the cause of my problems, there is a very
simple fix:
Windows provides InterlockedIncrement() and InterlockedDecrement()
functions to perform increments and decrements which are guaranteed to be atomic. So the fix is in thread/win32/SDL_syssem.c: replace occurrences of --sem->count with InterlockedDecrement(&sem->count); and replace occurrences of ++sem->count with InterlockedIncrement(&sem->count);
This is using SDL v1.2.12, built with VC++ 2008 Express, running on a
Core 2 duo processor.
author | Sam Lantinga <slouken@libsdl.org> |
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date | Fri, 28 Dec 2007 22:05:17 +0000 |
parents | 56ec4d962487 |
children |
rev | line source |
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0 | 1 #!/bin/sh |
2 | |
3 prefix=@prefix@ | |
4 exec_prefix=@exec_prefix@ | |
5 exec_prefix_set=no | |
3929
56ec4d962487
Date: Sat, 31 Mar 2007 16:39:52 +0200
Ryan C. Gordon <icculus@icculus.org>
parents:
1856
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6 libdir=@libdir@ |
0 | 7 |
1647
2af911d41a08
Date: Thu, 20 Apr 2006 10:13:34 +0200
Sam Lantinga <slouken@libsdl.org>
parents:
1548
diff
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8 @ENABLE_STATIC_FALSE@usage="\ |
2af911d41a08
Date: Thu, 20 Apr 2006 10:13:34 +0200
Sam Lantinga <slouken@libsdl.org>
parents:
1548
diff
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9 @ENABLE_STATIC_FALSE@Usage: sdl-config [--prefix[=DIR]] [--exec-prefix[=DIR]] [--version] [--cflags] [--libs]" |
2af911d41a08
Date: Thu, 20 Apr 2006 10:13:34 +0200
Sam Lantinga <slouken@libsdl.org>
parents:
1548
diff
changeset
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10 @ENABLE_STATIC_TRUE@usage="\ |
2af911d41a08
Date: Thu, 20 Apr 2006 10:13:34 +0200
Sam Lantinga <slouken@libsdl.org>
parents:
1548
diff
changeset
|
11 @ENABLE_STATIC_TRUE@Usage: sdl-config [--prefix[=DIR]] [--exec-prefix[=DIR]] [--version] [--cflags] [--libs] [--static-libs]" |
0 | 12 |
13 if test $# -eq 0; then | |
14 echo "${usage}" 1>&2 | |
15 exit 1 | |
16 fi | |
17 | |
18 while test $# -gt 0; do | |
19 case "$1" in | |
1856
21f13c787b46
Date: Mon, 22 May 2006 01:16:47 -0400
Sam Lantinga <slouken@libsdl.org>
parents:
1647
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20 -*=*) optarg=`echo "$1" | LC_ALL="C" sed 's/[-_a-zA-Z0-9]*=//'` ;; |
0 | 21 *) optarg= ;; |
22 esac | |
23 | |
24 case $1 in | |
25 --prefix=*) | |
26 prefix=$optarg | |
27 if test $exec_prefix_set = no ; then | |
28 exec_prefix=$optarg | |
29 fi | |
30 ;; | |
31 --prefix) | |
32 echo $prefix | |
33 ;; | |
34 --exec-prefix=*) | |
35 exec_prefix=$optarg | |
36 exec_prefix_set=yes | |
37 ;; | |
38 --exec-prefix) | |
39 echo $exec_prefix | |
40 ;; | |
41 --version) | |
42 echo @SDL_VERSION@ | |
43 ;; | |
44 --cflags) | |
490
7e53d17ec798
The portable way of including SDL is #include "SDL.h"
Sam Lantinga <slouken@libsdl.org>
parents:
296
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45 echo -I@includedir@/SDL @SDL_CFLAGS@ |
0 | 46 ;; |
47 @ENABLE_SHARED_TRUE@ --libs) | |
1548
a77c022733fe
EXTRA_LDFLAGS are the linker flags and libraries needed to build SDL.
Sam Lantinga <slouken@libsdl.org>
parents:
1361
diff
changeset
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48 @ENABLE_SHARED_TRUE@ echo -L@libdir@ @SDL_RLD_FLAGS@ @SDL_LIBS@ |
0 | 49 @ENABLE_SHARED_TRUE@ ;; |
50 @ENABLE_STATIC_TRUE@@ENABLE_SHARED_TRUE@ --static-libs) | |
51 @ENABLE_STATIC_TRUE@@ENABLE_SHARED_FALSE@ --libs|--static-libs) | |
1548
a77c022733fe
EXTRA_LDFLAGS are the linker flags and libraries needed to build SDL.
Sam Lantinga <slouken@libsdl.org>
parents:
1361
diff
changeset
|
52 @ENABLE_STATIC_TRUE@ echo -L@libdir@ @SDL_RLD_FLAGS@ @SDL_STATIC_LIBS@ |
0 | 53 @ENABLE_STATIC_TRUE@ ;; |
54 *) | |
55 echo "${usage}" 1>&2 | |
56 exit 1 | |
57 ;; | |
58 esac | |
59 shift | |
60 done |