[Mesa-dev] [PATCH] egl/drm: Try to use CLOEXEC for drm fds

[Emil Velikov]

Hi Derek,

On 1 May 2015 at 18:34, Derek Foreman <derekf at osg.samsung.com> wrote:
> These fds can propagate to child processes if we don't set CLOEXEC,
> so make a best effort to do that.
>
> Signed-off-by: Derek Foreman <derekf at osg.samsung.com>
> ---
> Noticed this when fixing up similar problems in weston - weston's
> drm fd gets dup()ed here and loses CLOEXEC and ends up in every child
> process the shell launches.
>
>  src/egl/drivers/dri2/platform_drm.c | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/src/egl/drivers/dri2/platform_drm.c b/src/egl/drivers/dri2/platform_drm.c
> index 486b003..c326d6c 100644
> --- a/src/egl/drivers/dri2/platform_drm.c
> +++ b/src/egl/drivers/dri2/platform_drm.c
> @@ -596,7 +596,11 @@ dri2_initialize_drm(_EGLDriver *drv, _EGLDisplay *disp)
>     struct dri2_egl_display *dri2_dpy;
>     struct gbm_device *gbm;
>     int fd = -1;
> -   int i;
> +   int i, flags = O_RDWR;
> +
> +#ifdef O_CLOEXEC
> +   flags |= O_CLOEXEC;
> +#endif
>
>     loader_set_logger(_eglLog);
>
> @@ -611,9 +615,9 @@ dri2_initialize_drm(_EGLDriver *drv, _EGLDisplay *disp)
>        char buf[64];
>        int n = snprintf(buf, sizeof(buf), DRM_DEV_NAME, DRM_DIR_NAME, 0);
>        if (n != -1 && n < sizeof(buf))
> -         fd = open(buf, O_RDWR);
> +         fd = open(buf, flags);
>        if (fd < 0)
> -         fd = open("/dev/dri/card0", O_RDWR);
> +         fd = open("/dev/dri/card0", flags);
>        dri2_dpy->own_device = 1;
>        gbm = gbm_create_device(fd);
>        if (gbm == NULL)
> @@ -639,6 +643,10 @@ dri2_initialize_drm(_EGLDriver *drv, _EGLDisplay *disp)
>        }
>     }
>
> +   flags = fcntl(dri2_dpy->fd, F_GETFD);
> +   if (flags >= 0 && !(flags & FD_CLOEXEC))
> +      fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
> +
In other places in mesa we explicitly check for EINVAL if open()
fails, and use that as indication that O_CLOEXEC is not supported
(note that we only use the O_RDWR and O_CLOEXEC flags). Curious which
would be the better approach to use through mesa ?

-Emil