Mercurial > sdl-ios-xcode
annotate src/thread/generic/SDL_syscond.c @ 1176:dd2a8deeb26d
Date: Mon, 17 Oct 2005 20:09:03 -0400
From: Mark Schreiber <mark7@alumni.cmu.edu>
To: ryan@clutteredmind.org
Subject: [PATCH]SDL mprotect() crash fix
(I'm going to throw this patch your way at the suggestion of #SDL --
for some reason, I had some difficulty sending it to the main list
last time, and I go bonkers subscribing to send each email or
patch...)
Currently, when I run SDL applications as non-root using
SDL_VIDEODRIVER=dga, the fbdev fallback mprotect()s read/write the
proper size of mmapped /dev/fb0 (7.5MB), but on framebuffer release
mprotect()s read-only the range by the entire size of my video memory
(128MB), which causes a segfault:
#0 0x002a9a27 in ?? () from /lib/libc.so.6
#1 0x04a63eb6 in SDL_XDGAUnmapFramebuffer (screen=3D0) at XF86DGA2.c:978
#2 0x04a63efc in SDL_XDGACloseFramebuffer (dpy=3D0x9d3f008, screen=3D0)
at XF86DGA2.c:268
#3 0x04a68b57 in DGA_Available () at SDL_dgavideo.c:98
#4 0x04a53677 in SDL_VideoInit (driver_name=3D0xbfb0bfc7 "dga", flags=3D0)
at SDL_video.c:180
#5 0x04a2613f in SDL_InitSubSystem (flags=3D32) at SDL.c:74
#6 0x04a2617c in SDL_Init (flags=3D32) at SDL.c:166
#7 0x08049722 in main (argc=3D1, argv=3D0x0) at testwin.c:32
This is SDL 1.2.8 on Fedora Core 4, radeon driver for a Radeon 9250,
xorg-x11-6.8.2-37.
I've attached a one-line patch against SDL CVS that updates the size
of the framebuffer at framebuffer map time so that the mprotect() on
unmap will be the same size. I'm not sure if this is the best
approach (i.e. one might want to retain the original value), but it
does make my SDL applications work without segfaulting.
-- Best of luck, Mark Schreiber
| author | Ryan C. Gordon <icculus@icculus.org> |
|---|---|
| date | Sat, 19 Nov 2005 18:57:00 +0000 |
| parents | b8d311d90021 |
| children | c9b51268668f |
| rev | line source |
|---|---|
| 0 | 1 /* |
| 2 SDL - Simple DirectMedia Layer | |
|
769
b8d311d90021
Updated copyright information for 2004 (Happy New Year!)
Sam Lantinga <slouken@libsdl.org>
parents:
297
diff
changeset
|
3 Copyright (C) 1997-2004 Sam Lantinga |
| 0 | 4 |
| 5 This library is free software; you can redistribute it and/or | |
| 6 modify it under the terms of the GNU Library General Public | |
| 7 License as published by the Free Software Foundation; either | |
| 8 version 2 of the License, or (at your option) any later version. | |
| 9 | |
| 10 This library is distributed in the hope that it will be useful, | |
| 11 but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
| 13 Library General Public License for more details. | |
| 14 | |
| 15 You should have received a copy of the GNU Library General Public | |
| 16 License along with this library; if not, write to the Free | |
| 17 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA | |
| 18 | |
| 19 Sam Lantinga | |
|
252
e8157fcb3114
Updated the source with the correct e-mail address
Sam Lantinga <slouken@libsdl.org>
parents:
0
diff
changeset
|
20 slouken@libsdl.org |
| 0 | 21 */ |
| 22 | |
| 23 #ifdef SAVE_RCSID | |
| 24 static char rcsid = | |
| 25 "@(#) $Id$"; | |
| 26 #endif | |
| 27 | |
| 28 /* An implementation of condition variables using semaphores and mutexes */ | |
| 29 /* | |
| 30 This implementation borrows heavily from the BeOS condition variable | |
| 31 implementation, written by Christopher Tate and Owen Smith. Thanks! | |
| 32 */ | |
| 33 | |
| 34 #include <stdio.h> | |
| 35 #include <stdlib.h> | |
| 36 | |
| 37 #include "SDL_error.h" | |
| 38 #include "SDL_thread.h" | |
| 39 | |
| 40 struct SDL_cond | |
| 41 { | |
| 42 SDL_mutex *lock; | |
| 43 int waiting; | |
| 44 int signals; | |
| 45 SDL_sem *wait_sem; | |
| 46 SDL_sem *wait_done; | |
| 47 }; | |
| 48 | |
| 49 /* Create a condition variable */ | |
| 50 SDL_cond * SDL_CreateCond(void) | |
| 51 { | |
| 52 SDL_cond *cond; | |
| 53 | |
| 54 cond = (SDL_cond *) malloc(sizeof(SDL_cond)); | |
| 55 if ( cond ) { | |
| 56 cond->lock = SDL_CreateMutex(); | |
| 57 cond->wait_sem = SDL_CreateSemaphore(0); | |
| 58 cond->wait_done = SDL_CreateSemaphore(0); | |
| 59 cond->waiting = cond->signals = 0; | |
| 60 if ( ! cond->lock || ! cond->wait_sem || ! cond->wait_done ) { | |
| 61 SDL_DestroyCond(cond); | |
| 62 cond = NULL; | |
| 63 } | |
| 64 } else { | |
| 65 SDL_OutOfMemory(); | |
| 66 } | |
| 67 return(cond); | |
| 68 } | |
| 69 | |
| 70 /* Destroy a condition variable */ | |
| 71 void SDL_DestroyCond(SDL_cond *cond) | |
| 72 { | |
| 73 if ( cond ) { | |
| 74 if ( cond->wait_sem ) { | |
| 75 SDL_DestroySemaphore(cond->wait_sem); | |
| 76 } | |
| 77 if ( cond->wait_done ) { | |
| 78 SDL_DestroySemaphore(cond->wait_done); | |
| 79 } | |
| 80 if ( cond->lock ) { | |
| 81 SDL_DestroyMutex(cond->lock); | |
| 82 } | |
| 83 free(cond); | |
| 84 } | |
| 85 } | |
| 86 | |
| 87 /* Restart one of the threads that are waiting on the condition variable */ | |
| 88 int SDL_CondSignal(SDL_cond *cond) | |
| 89 { | |
| 90 if ( ! cond ) { | |
| 91 SDL_SetError("Passed a NULL condition variable"); | |
| 92 return -1; | |
| 93 } | |
| 94 | |
| 95 /* If there are waiting threads not already signalled, then | |
| 96 signal the condition and wait for the thread to respond. | |
| 97 */ | |
| 98 SDL_LockMutex(cond->lock); | |
| 99 if ( cond->waiting > cond->signals ) { | |
| 100 ++cond->signals; | |
| 101 SDL_SemPost(cond->wait_sem); | |
| 102 SDL_UnlockMutex(cond->lock); | |
| 103 SDL_SemWait(cond->wait_done); | |
| 104 } else { | |
| 105 SDL_UnlockMutex(cond->lock); | |
| 106 } | |
| 107 | |
| 108 return 0; | |
| 109 } | |
| 110 | |
| 111 /* Restart all threads that are waiting on the condition variable */ | |
| 112 int SDL_CondBroadcast(SDL_cond *cond) | |
| 113 { | |
| 114 if ( ! cond ) { | |
| 115 SDL_SetError("Passed a NULL condition variable"); | |
| 116 return -1; | |
| 117 } | |
| 118 | |
| 119 /* If there are waiting threads not already signalled, then | |
| 120 signal the condition and wait for the thread to respond. | |
| 121 */ | |
| 122 SDL_LockMutex(cond->lock); | |
| 123 if ( cond->waiting > cond->signals ) { | |
| 124 int i, num_waiting; | |
| 125 | |
| 126 num_waiting = (cond->waiting - cond->signals); | |
| 127 cond->signals = cond->waiting; | |
| 128 for ( i=0; i<num_waiting; ++i ) { | |
| 129 SDL_SemPost(cond->wait_sem); | |
| 130 } | |
| 131 /* Now all released threads are blocked here, waiting for us. | |
| 132 Collect them all (and win fabulous prizes!) :-) | |
| 133 */ | |
| 134 SDL_UnlockMutex(cond->lock); | |
| 135 for ( i=0; i<num_waiting; ++i ) { | |
| 136 SDL_SemWait(cond->wait_done); | |
| 137 } | |
| 138 } else { | |
| 139 SDL_UnlockMutex(cond->lock); | |
| 140 } | |
| 141 | |
| 142 return 0; | |
| 143 } | |
| 144 | |
| 145 /* Wait on the condition variable for at most 'ms' milliseconds. | |
| 146 The mutex must be locked before entering this function! | |
| 147 The mutex is unlocked during the wait, and locked again after the wait. | |
| 148 | |
| 149 Typical use: | |
| 150 | |
| 151 Thread A: | |
| 152 SDL_LockMutex(lock); | |
| 153 while ( ! condition ) { | |
| 154 SDL_CondWait(cond); | |
| 155 } | |
| 156 SDL_UnlockMutex(lock); | |
| 157 | |
| 158 Thread B: | |
| 159 SDL_LockMutex(lock); | |
| 160 ... | |
| 161 condition = true; | |
| 162 ... | |
| 163 SDL_UnlockMutex(lock); | |
| 164 */ | |
| 165 int SDL_CondWaitTimeout(SDL_cond *cond, SDL_mutex *mutex, Uint32 ms) | |
| 166 { | |
| 167 int retval; | |
| 168 | |
| 169 if ( ! cond ) { | |
| 170 SDL_SetError("Passed a NULL condition variable"); | |
| 171 return -1; | |
| 172 } | |
| 173 | |
| 174 /* Obtain the protection mutex, and increment the number of waiters. | |
| 175 This allows the signal mechanism to only perform a signal if there | |
| 176 are waiting threads. | |
| 177 */ | |
| 178 SDL_LockMutex(cond->lock); | |
| 179 ++cond->waiting; | |
| 180 SDL_UnlockMutex(cond->lock); | |
| 181 | |
| 182 /* Unlock the mutex, as is required by condition variable semantics */ | |
| 183 SDL_UnlockMutex(mutex); | |
| 184 | |
| 185 /* Wait for a signal */ | |
| 186 if ( ms == SDL_MUTEX_MAXWAIT ) { | |
| 187 retval = SDL_SemWait(cond->wait_sem); | |
| 188 } else { | |
| 189 retval = SDL_SemWaitTimeout(cond->wait_sem, ms); | |
| 190 } | |
| 191 | |
| 192 /* Let the signaler know we have completed the wait, otherwise | |
| 193 the signaler can race ahead and get the condition semaphore | |
| 194 if we are stopped between the mutex unlock and semaphore wait, | |
| 195 giving a deadlock. See the following URL for details: | |
| 196 http://www-classic.be.com/aboutbe/benewsletter/volume_III/Issue40.html | |
| 197 */ | |
| 198 SDL_LockMutex(cond->lock); | |
| 199 if ( cond->signals > 0 ) { | |
| 200 /* If we timed out, we need to eat a condition signal */ | |
| 201 if ( retval > 0 ) { | |
| 202 SDL_SemWait(cond->wait_sem); | |
| 203 } | |
| 204 /* We always notify the signal thread that we are done */ | |
| 205 SDL_SemPost(cond->wait_done); | |
| 206 | |
| 207 /* Signal handshake complete */ | |
| 208 --cond->signals; | |
| 209 } | |
| 210 --cond->waiting; | |
| 211 SDL_UnlockMutex(cond->lock); | |
| 212 | |
| 213 /* Lock the mutex, as is required by condition variable semantics */ | |
| 214 SDL_LockMutex(mutex); | |
| 215 | |
| 216 return retval; | |
| 217 } | |
| 218 | |
| 219 /* Wait on the condition variable forever */ | |
| 220 int SDL_CondWait(SDL_cond *cond, SDL_mutex *mutex) | |
| 221 { | |
| 222 return SDL_CondWaitTimeout(cond, mutex, SDL_MUTEX_MAXWAIT); | |
| 223 } |