[Mesa-users] Mesa XWindows memory leak causing application instability
Rick Irons
Rick.Irons at mathworks.com
Fri Jun 16 20:17:33 UTC 2017
Hi Brian,
We are using the old Mesa Xlib driver. The configure options we use are the following...
./autogen.sh --enable-glx=xlib --disable-driglx-direct --disable-dri --without-gallium-drivers --disable-egl --disable-gbm -with-platforms=x11
Output of glxinfo is attached.
Thanks,
Rick
-----Original Message-----
From: Brian Paul [mailto:brianp at vmware.com]
Sent: Friday, June 16, 2017 4:06 PM
To: Rick Irons <Rick.Irons at mathworks.com>
Cc: Chuck Atkins <chuck.atkins at kitware.com>; mesa-users at lists.freedesktop.org
Subject: Re: [Mesa-users] Mesa XWindows memory leak causing application instability
Rick,
Which Mesa driver are you using? What's the output of glxinfo?
Both the old Mesa Xlib driver and the newer gallium softpipe/llvmpipe drivers use XShm and I'm not sure which one you're using.
-Brian
On 06/16/2017 01:28 PM, Chuck Atkins wrote:
> Hi Rick,
> If you file a bug report it will usually get looked at by the
> necessary devs. If you don't hear anything back on the bug after a
> few days then try the dev list directly. You can also check the IRC
> channel #dri-devel on freenode.
>
> - Chuck
>
> On Tue, Jun 13, 2017 at 12:10 PM, Rick Irons <Rick.Irons at mathworks.com
> <mailto:Rick.Irons at mathworks.com>> wrote:
>
> Hi all,____
>
> __ __
>
> Any thoughts on the issue identified below? ____
>
> __ __
>
> Perhaps this issue is something for the mesa-dev mailing list.____
>
> __ __
>
> Thanks,____
>
> Rick____
>
> __ __
>
> *From:* Rick Irons
> *Sent:* Friday, June 9, 2017 5:59 PM
> *To:* mesa-users at lists.freedesktop.org
> <mailto:mesa-users at lists.freedesktop.org>
> *Subject:* Mesa XWindows memory leak causing application
> instability____
>
> __ __
>
> Hi,____
>
> __ __
>
> We are encountering sporadic application instability with an
> XWindows based implementation of Mesa. The source of the
> instability appears to be a memory leak. The details of our
> investigation are included below.____
>
> __ __
>
> This issue appears to have been introduced in Mesa 8.0.0 and is
> present in the current 17.1.2 release.____
>
> __ __
>
> Our workaround is identified below. We are interested to know if
> this is a valid fix or if there is an alternative preferred approach
> to addressing the problem.____
>
> __ __
>
> Thanks for any help that you can provide.____
>
> __ __
>
> Rick____
>
> __ __
>
> __ __
>
> __ __
>
> *Problem description:____*
>
> It looks like Mesa is dependent on MIT-SHM extension in the sense
> that if the MIT-SHM loads, it needs to be left in the same state
> such that Mesa's call to XShmDetatch() works correctly, with no
> unintended side-effects.____
>
> __ __
>
> The order of extension "close" callbacks appear to be driven by a
> loop in XCloseDisplay() where "Display *" points to a linked-list
> identified in the "ext_procs" field.____
>
> __ __
>
> We find that in Mesa’s current state, MIT-SHM's close_display
> extension hook is called _before_ Mesa's extension hook has been
> called. Thus, MIT-SHM's shm_info has removed/deleted the
> _XExtDisplayInfo entry associated with the Display * being closed
> _before_ Mesa has called XShmDetach as part of its close
> callback.____
>
> __ __
>
> The effect is to create a new _XExtDisplayInfo pointer that's left
> pointing to a freed "codes" field. If the _next_ caller of
> XOpenDisplay() is unlucky enough to a) obtain a recycled address of
> a "Display *" matching the previous one and b) call
> XShmQueryVersion(), there is a chance that the "codes" value(s) have
> been overwritten resulting in XError of BadRequest, BadLength, or
> hanging (all have been observed). This appears to be what
> https://github.com/mesa3d/mesa/commit/0a20051e6da99e91b7bf589ea457c77a8b618f26
> <https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_mesa3d_mesa_commit_0a20051e6da99e91b7bf589ea457c77a8b618f26&d=DwMFaQ&c=uilaK90D4TOVoH58JNXRgQ&r=Ie7_encNUsqxbSRbqbNgofw0ITcfE8JKfaUjIQhncGA&m=sDFaHTXy_QwKdQ0mlORDT6cCzkRnbjEwsqTMtCQJVsY&s=WErP_2_7ibjVwY_O0qnVjtrreVBAWiiSUt7LW_qKVxg&e=>
> alludes to. In fact, I added XShmQueryVersion() back in to xm_api.c,
> removed the XShmQueryVersion() I'd incorporated into glxgears-based
> test program, and reproduced this failure:____
>
> __ __
>
> X Error of failed request: BadRequest (invalid request code or no
> such operation)____
>
> Major opcode of failed request: 0 ()____
>
> Serial number of failed request: 17____
>
> Current serial number in output stream: 17 ____
>
> __ __
>
> which is exactly what we see when our glxgears-based test program
> calls XShmQueryVersion() after a few loops.____
>
> __ __
>
> *Reproduction:____*
>
> See the modified "glxgears" demo. If possible, run on Debian 8.3 and
> keep hitting escape to close the current gears demo window and
> advance the loop. ____
>
> __ __
>
> *Possible workaround:____*
>
> If src/mesa/drivers/x11/fakeglx.c references MIT-SHM _before_
> registering itself as an extension with the current display, this
> appears to allow Mesa's call to XShmDetach to occur with no
> unintended consequence. MIT-SHM's close callback is called _after_
> Mesa has performed its clean up and we see no stranded entries in
> shm_info associated with the current display.____
>
> __ __
>
>
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