XFree86 Bug/Test Report Form
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VERSION:
CVS tree on 1/21/2003
XF86_VERSION
4.2.99.4
VIDEO DRIVER:
radeon mobile 9600
OPERATING SYSTEM:
Linux
VIDEO CARD:
MODEL:
Radeon Mobility 9000
GRAPHICS CHIPSET:
ATI Radeon R250
RAMDAC:
CLOCKCHIP:
VIDEO MEMORY:
BUS TYPE:
PCI
REPORT:
I have an OpenGL program that crashes after opening the GL
context (I believe) - but then dies. The Xserver tries to cleanup
after this mishap and free memory. In the Mesa server code,
xc/extras/Mesa/src/tnl, a context structure element "freed_immesiate"
is used to cache the last freed memory - for possible reuse. Clearly a
performance gain.
The problem: If no memory has been freed - because none has been
allocated yet, _tnl_DestroyContext (t_context.c:146) invokes
_tnl_free_immediate with a second argument the pointer to the
freed_immediate memory. This will be "0" if no memory has been freed -
or if t_imm_alloc.c has given the memory to someone else already.
_tnl_free_immediate (t_imm_alloc.c:129) places the second argument into a
variable IM.
Almost immediately at line 130 - IM is derefenced with
ASSERT(IM->ref_count == 0);
Oops....
Two possible fixes: a) _tnl_free_immediate should test for IM being 0,
or _tnl_DestroyContext should not call _tnl_free_immediate if freed_immediate
is 0.
I chose the later.... Seems that the DRI development CVS tree suffers
from the same.
Ezra
--- xc/extras/Mesa/src/tnl/t_context.c.ezra 2003-01-27 17:22:23.000000000 -0500
+++ xc/extras/Mesa/src/tnl/t_context.c 2003-01-27 17:11:58.000000000 -0500
@@ -144,7 +144,8 @@
_tnl_array_destroy( ctx );
_tnl_imm_destroy( ctx );
_tnl_destroy_pipeline( ctx );
- _tnl_free_immediate( ctx, tnl->freed_immediate );
+ if (tnl->freed_immediate)
+ _tnl_free_immediate( ctx, tnl->freed_immediate );
FREE(tnl);
ctx->swtnl_context = 0;
$XFree86: xc/programs/Xserver/hw/xfree86/doc/BugReport.cpp,v 1.1 2001/01/15 23:00:01
dawes Exp $
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