[Mesa-dev] [PATCH] winsys/sw/xlib: Prevent shared memory segment leakage.

[Brian Paul]

On 04/24/2013 03:54 AM, jfonseca at vmware.com wrote:
> From: José Fonseca<jfonseca at vmware.com>
>
> Running piglit with this was causing all sort of weird stuff happening
> to my desktop (Chromium webpages become blank, Qt Creator flickered,
> etc).  I tracked this down to shared memory segment leakage when GL is
> not shutdown properly. The segments can be seen running `ipcs` and
> looking for nattch==0.
>
> This changes fixes this by calling shmctl(IPC_RMID) soon after creation
> (which does not remove the segment immediately, but simply marks it for
> removal when no more processes are attached).
>
> This matches src/mesa/drivers/x11/xm_buffer.c behaviour.
>
> v2:
> - move shmctl(IPC_RMID) after XShmAttach() for *BSD, per Chris Wilson
> - remove stray debug printfs, spotted by Ian Romanick
>
> NOTE: This is a candidate for stable branches.
> ---
>   src/gallium/winsys/sw/xlib/xlib_sw_winsys.c |    6 ++++++
>   1 file changed, 6 insertions(+)
>
> diff --git a/src/gallium/winsys/sw/xlib/xlib_sw_winsys.c b/src/gallium/winsys/sw/xlib/xlib_sw_winsys.c
> index 3aef8da..6e71530 100644
> --- a/src/gallium/winsys/sw/xlib/xlib_sw_winsys.c
> +++ b/src/gallium/winsys/sw/xlib/xlib_sw_winsys.c
> @@ -165,6 +165,7 @@ alloc_shm_ximage(struct xlib_displaytarget *xlib_dt,
>                                         &xlib_dt->shminfo,
>                                         width, height);
>      if (xlib_dt->tempImage == NULL) {
> +      shmctl(xlib_dt->shminfo.shmid, IPC_RMID, 0);
>         xlib_dt->shm = False;
>         return;
>      }
> @@ -176,6 +177,11 @@ alloc_shm_ximage(struct xlib_displaytarget *xlib_dt,
>      XShmAttach(xlib_dt->display,&xlib_dt->shminfo);
>      XSync(xlib_dt->display, False);
>
> +   /* Mark the segment to be destroyed, so that it is automatically destroyed
> +    * when this process dies.  Needs to be after XShmAttach() for *BSD.
> +    */
> +   shmctl(xlib_dt->shminfo.shmid, IPC_RMID, 0);
> +
>      if (XErrorFlag) {
>         /* we are on a remote display, this error is normal, don't print it */
>         XFlush(xlib_dt->display);

Reviewed-by: Brian Paul <brianp at vmware.com>

Thanks for fixing this.  I've been aware of this for a while and had 
been meaning to fix it too.

-Brian