[Mesa-dev] [PATCH v4 03/11] gallium: add common pipe_screen reference counting functions

[Ilia Mirkin]

On Fri, Jul 22, 2016 at 12:22 PM, Rob Herring <robh at kernel.org> wrote:
> In order to prevent multiple pipe_screens being created in the same
> process, lookup of the DRM FD and reference counting of the pipe_screen
> are needed. Several implementations of this exist in various gallium
> drivers/winsys already. This creates a common version which is opt-in
> for winsys implementations.
>
> Signed-off-by: Rob Herring <robh at kernel.org>
> ---
>  src/gallium/auxiliary/Makefile.sources |   2 +
>  src/gallium/auxiliary/util/u_screen.c  | 114 +++++++++++++++++++++++++++++++++
>  src/gallium/auxiliary/util/u_screen.h  |  32 +++++++++
>  src/gallium/include/pipe/p_screen.h    |   3 +
>  4 files changed, 151 insertions(+)
>  create mode 100644 src/gallium/auxiliary/util/u_screen.c
>  create mode 100644 src/gallium/auxiliary/util/u_screen.h
>
> diff --git a/src/gallium/auxiliary/Makefile.sources b/src/gallium/auxiliary/Makefile.sources
> index e0311bf..197ed36 100644
> --- a/src/gallium/auxiliary/Makefile.sources
> +++ b/src/gallium/auxiliary/Makefile.sources
> @@ -284,6 +284,8 @@ C_SOURCES := \
>         util/u_ringbuffer.h \
>         util/u_sampler.c \
>         util/u_sampler.h \
> +       util/u_screen.c \
> +       util/u_screen.h \
>         util/u_simple_shaders.c \
>         util/u_simple_shaders.h \
>         util/u_slab.c \
> diff --git a/src/gallium/auxiliary/util/u_screen.c b/src/gallium/auxiliary/util/u_screen.c
> new file mode 100644
> index 0000000..47bad11
> --- /dev/null
> +++ b/src/gallium/auxiliary/util/u_screen.c
> @@ -0,0 +1,114 @@
> +/*
> + * Copyright 2016 Linaro, Ltd., Rob Herring <robh at kernel.org>
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the
> + * "Software"), to deal in the Software without restriction, including
> + * without limitation the rights to use, copy, modify, merge, publish,
> + * distribute, sub license, and/or sell copies of the Software, and to
> + * permit persons to whom the Software is furnished to do so, subject to
> + * the following conditions:
> + *
> + * The above copyright notice and this permission notice (including the
> + * next paragraph) shall be included in all copies or substantial portions
> + * of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
> + * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
> + * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
> + * IN NO EVENT SHALL VMWARE AND/OR ITS SUPPLIERS BE LIABLE FOR
> + * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
> + * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
> + * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
> + */
> +
> +/**
> + * Functions for managing pipe_screen's
> + */
> +
> +#include <sys/stat.h>
> +
> +#include "os/os_thread.h"
> +
> +#include "pipe/p_screen.h"
> +#include "util/u_hash_table.h"
> +#include "util/u_inlines.h"
> +#include "util/u_pointer.h"
> +#include "util/u_screen.h"
> +
> +static struct util_hash_table *fd_tab = NULL;
> +pipe_static_mutex(fd_tab_mutex);
> +
> +static unsigned hash_fd(void *key)
> +{
> +   int fd = pointer_to_intptr(key);
> +   struct stat stat;
> +   fstat(fd, &stat);
> +
> +   return stat.st_dev ^ stat.st_ino ^ stat.st_rdev;
> +}
> +
> +static int compare_fd(void *key1, void *key2)
> +{
> +   int fd1 = pointer_to_intptr(key1);
> +   int fd2 = pointer_to_intptr(key2);
> +   struct stat stat1, stat2;
> +   fstat(fd1, &stat1);
> +   fstat(fd2, &stat2);
> +
> +   return stat1.st_dev != stat2.st_dev ||
> +         stat1.st_ino != stat2.st_ino ||
> +         stat1.st_rdev != stat2.st_rdev;
> +}
> +
> +struct pipe_screen *
> +pipe_screen_reference(int fd)
> +{
> +   struct pipe_screen *pscreen;
> +
> +   if (!fd_tab) {
> +      fd_tab = util_hash_table_create(hash_fd, compare_fd);

Do you need to grab the fd_tab_mutex around this? What if two
pipe_screen_reference() calls race to be the first ones?

> +      return NULL;
> +   }
> +
> +   pipe_mutex_lock(fd_tab_mutex);
> +   pscreen = util_hash_table_get(fd_tab, intptr_to_pointer(fd));
> +   if (pscreen)
> +      pipe_reference(NULL, &pscreen->reference);
> +   pipe_mutex_unlock(fd_tab_mutex);
> +
> +   return pscreen;
> +}
> +
> +boolean
> +pipe_screen_unreference(struct pipe_screen *pscreen)
> +{
> +   boolean destroy;
> +
> +   if (!pscreen)
> +      return FALSE;
> +
> +   /* Work-around until all pipe_screens have ref counting */
> +   if (!pipe_is_referenced(&pscreen->reference)) {
> +      pscreen->destroy(pscreen);
> +      return TRUE;
> +   }
> +
> +   pipe_mutex_lock(fd_tab_mutex);
> +   destroy = pipe_reference(&pscreen->reference, NULL);
> +   if (destroy) {
> +      pscreen->destroy(pscreen);
> +      util_hash_table_remove(fd_tab, intptr_to_pointer(pscreen->fd));
> +      close(pscreen->fd);

It seems a little odd that you're closing a fd that you didn't
open/dup in this library. It's a bit of asymmetry in the calling
convention.

Your call if you want to flip it, but if you don't, I'd appreciate a
bit of doc somewhere about it.

> +   }
> +   pipe_mutex_unlock(fd_tab_mutex);
> +   return destroy;
> +}
> +
> +
> +void pipe_screen_reference_init(struct pipe_screen *pscreen, int fd)
> +{
> +   pscreen->fd = fd;
> +   pipe_reference_init(&pscreen->reference, 1);
> +   util_hash_table_set(fd_tab, intptr_to_pointer(pscreen->fd), pscreen);
> +}
> diff --git a/src/gallium/auxiliary/util/u_screen.h b/src/gallium/auxiliary/util/u_screen.h
> new file mode 100644
> index 0000000..fc91782
> --- /dev/null
> +++ b/src/gallium/auxiliary/util/u_screen.h
> @@ -0,0 +1,32 @@
> +/*
> + * Copyright 2016 Linaro, Ltd., Rob Herring <robh at kernel.org>
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the
> + * "Software"), to deal in the Software without restriction, including
> + * without limitation the rights to use, copy, modify, merge, publish,
> + * distribute, sub license, and/or sell copies of the Software, and to
> + * permit persons to whom the Software is furnished to do so, subject to
> + * the following conditions:
> + *
> + * The above copyright notice and this permission notice (including the
> + * next paragraph) shall be included in all copies or substantial portions
> + * of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
> + * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
> + * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
> + * IN NO EVENT SHALL VMWARE AND/OR ITS SUPPLIERS BE LIABLE FOR
> + * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
> + * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
> + * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
> + */
> +#include "pipe/p_defines.h"
> +
> +struct pipe_screen;
> +
> +struct pipe_screen *pipe_screen_reference(int fd);
> +
> +boolean pipe_screen_unreference(struct pipe_screen *pscreen);
> +
> +void pipe_screen_reference_init(struct pipe_screen *pscreen, int fd);
> diff --git a/src/gallium/include/pipe/p_screen.h b/src/gallium/include/pipe/p_screen.h
> index 755291a..1119bde 100644
> --- a/src/gallium/include/pipe/p_screen.h
> +++ b/src/gallium/include/pipe/p_screen.h
> @@ -41,6 +41,7 @@
>  #include "pipe/p_compiler.h"
>  #include "pipe/p_format.h"
>  #include "pipe/p_defines.h"
> +#include "pipe/p_state.h"
>  #include "pipe/p_video_enums.h"
>
>
> @@ -66,6 +67,8 @@ struct pipe_memory_info;
>   * context.
>   */
>  struct pipe_screen {
> +   struct pipe_reference reference;
> +   int fd;
>     void (*destroy)( struct pipe_screen * );
>
>     const char *(*get_name)( struct pipe_screen * );
> --
> 2.9.2
>