Mercurial > sdl-ios-xcode
view 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 |
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/* SDL - Simple DirectMedia Layer Copyright (C) 1997-2004 Sam Lantinga This library is free software; you can redistribute it and/or modify it under the terms of the GNU Library General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public License for more details. You should have received a copy of the GNU Library General Public License along with this library; if not, write to the Free Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA Sam Lantinga slouken@libsdl.org */ #ifdef SAVE_RCSID static char rcsid = "@(#) $Id$"; #endif /* An implementation of condition variables using semaphores and mutexes */ /* This implementation borrows heavily from the BeOS condition variable implementation, written by Christopher Tate and Owen Smith. Thanks! */ #include <stdio.h> #include <stdlib.h> #include "SDL_error.h" #include "SDL_thread.h" struct SDL_cond { SDL_mutex *lock; int waiting; int signals; SDL_sem *wait_sem; SDL_sem *wait_done; }; /* Create a condition variable */ SDL_cond * SDL_CreateCond(void) { SDL_cond *cond; cond = (SDL_cond *) malloc(sizeof(SDL_cond)); if ( cond ) { cond->lock = SDL_CreateMutex(); cond->wait_sem = SDL_CreateSemaphore(0); cond->wait_done = SDL_CreateSemaphore(0); cond->waiting = cond->signals = 0; if ( ! cond->lock || ! cond->wait_sem || ! cond->wait_done ) { SDL_DestroyCond(cond); cond = NULL; } } else { SDL_OutOfMemory(); } return(cond); } /* Destroy a condition variable */ void SDL_DestroyCond(SDL_cond *cond) { if ( cond ) { if ( cond->wait_sem ) { SDL_DestroySemaphore(cond->wait_sem); } if ( cond->wait_done ) { SDL_DestroySemaphore(cond->wait_done); } if ( cond->lock ) { SDL_DestroyMutex(cond->lock); } free(cond); } } /* Restart one of the threads that are waiting on the condition variable */ int SDL_CondSignal(SDL_cond *cond) { if ( ! cond ) { SDL_SetError("Passed a NULL condition variable"); return -1; } /* If there are waiting threads not already signalled, then signal the condition and wait for the thread to respond. */ SDL_LockMutex(cond->lock); if ( cond->waiting > cond->signals ) { ++cond->signals; SDL_SemPost(cond->wait_sem); SDL_UnlockMutex(cond->lock); SDL_SemWait(cond->wait_done); } else { SDL_UnlockMutex(cond->lock); } return 0; } /* Restart all threads that are waiting on the condition variable */ int SDL_CondBroadcast(SDL_cond *cond) { if ( ! cond ) { SDL_SetError("Passed a NULL condition variable"); return -1; } /* If there are waiting threads not already signalled, then signal the condition and wait for the thread to respond. */ SDL_LockMutex(cond->lock); if ( cond->waiting > cond->signals ) { int i, num_waiting; num_waiting = (cond->waiting - cond->signals); cond->signals = cond->waiting; for ( i=0; i<num_waiting; ++i ) { SDL_SemPost(cond->wait_sem); } /* Now all released threads are blocked here, waiting for us. Collect them all (and win fabulous prizes!) :-) */ SDL_UnlockMutex(cond->lock); for ( i=0; i<num_waiting; ++i ) { SDL_SemWait(cond->wait_done); } } else { SDL_UnlockMutex(cond->lock); } return 0; } /* Wait on the condition variable for at most 'ms' milliseconds. The mutex must be locked before entering this function! The mutex is unlocked during the wait, and locked again after the wait. Typical use: Thread A: SDL_LockMutex(lock); while ( ! condition ) { SDL_CondWait(cond); } SDL_UnlockMutex(lock); Thread B: SDL_LockMutex(lock); ... condition = true; ... SDL_UnlockMutex(lock); */ int SDL_CondWaitTimeout(SDL_cond *cond, SDL_mutex *mutex, Uint32 ms) { int retval; if ( ! cond ) { SDL_SetError("Passed a NULL condition variable"); return -1; } /* Obtain the protection mutex, and increment the number of waiters. This allows the signal mechanism to only perform a signal if there are waiting threads. */ SDL_LockMutex(cond->lock); ++cond->waiting; SDL_UnlockMutex(cond->lock); /* Unlock the mutex, as is required by condition variable semantics */ SDL_UnlockMutex(mutex); /* Wait for a signal */ if ( ms == SDL_MUTEX_MAXWAIT ) { retval = SDL_SemWait(cond->wait_sem); } else { retval = SDL_SemWaitTimeout(cond->wait_sem, ms); } /* Let the signaler know we have completed the wait, otherwise the signaler can race ahead and get the condition semaphore if we are stopped between the mutex unlock and semaphore wait, giving a deadlock. See the following URL for details: http://www-classic.be.com/aboutbe/benewsletter/volume_III/Issue40.html */ SDL_LockMutex(cond->lock); if ( cond->signals > 0 ) { /* If we timed out, we need to eat a condition signal */ if ( retval > 0 ) { SDL_SemWait(cond->wait_sem); } /* We always notify the signal thread that we are done */ SDL_SemPost(cond->wait_done); /* Signal handshake complete */ --cond->signals; } --cond->waiting; SDL_UnlockMutex(cond->lock); /* Lock the mutex, as is required by condition variable semantics */ SDL_LockMutex(mutex); return retval; } /* Wait on the condition variable forever */ int SDL_CondWait(SDL_cond *cond, SDL_mutex *mutex) { return SDL_CondWaitTimeout(cond, mutex, SDL_MUTEX_MAXWAIT); }