[Mesa-dev] [PATCH 3/3] st/mesa: guard sampler views changes with a mutex
Marek Olšák
maraeo at gmail.com
Fri Oct 27 22:14:48 UTC 2017
For the series:
Reviewed-by: Marek Olšák <marek.olsak at amd.com>
Marek
On Sun, Oct 22, 2017 at 8:39 PM, Nicolai Hähnle <nhaehnle at gmail.com> wrote:
> From: Nicolai Hähnle <nicolai.haehnle at amd.com>
>
> Some locking is unfortunately required, because well-formed GL programs
> can have multiple threads racing to access the same texture, e.g.: two
> threads/contexts rendering from the same texture, or one thread destroying
> a context while the other is rendering from or modifying a texture.
>
> Since even the simple mutex caused noticable slowdowns in the piglit
> drawoverhead micro-benchmark, this patch uses a slightly more involved
> approach to keep locks out of the fast path:
>
> - the initial lookup of sampler views happens without taking a lock
> - a per-texture lock is only taken when we have to modify the sampler
> view(s)
> - since each thread mostly operates only on the entry corresponding to
> its context, the main issue is re-allocation of the sampler view array
> when it needs to be grown, but the old copy is not freed
>
> Old copies of the sampler views array are kept around in a linked list
> until the entire texture object is deleted. The total memory wasted
> in this way is roughly equal to the size of the current sampler views
> array.
>
> Fixes non-deterministic memory corruption in some
> dEQP-EGL.functional.sharing.gles2.multithread.* tests, e.g.
> dEQP-EGL.functional.sharing.gles2.multithread.simple.images.texture_source.create_texture_render
> ---
> src/mesa/state_tracker/st_atom_sampler.c | 21 +--
> src/mesa/state_tracker/st_cb_texture.c | 12 ++
> src/mesa/state_tracker/st_sampler_view.c | 270 ++++++++++++++++++++++---------
> src/mesa/state_tracker/st_sampler_view.h | 3 +
> src/mesa/state_tracker/st_texture.h | 40 ++++-
> 5 files changed, 250 insertions(+), 96 deletions(-)
>
> diff --git a/src/mesa/state_tracker/st_atom_sampler.c b/src/mesa/state_tracker/st_atom_sampler.c
> index ff3f49fa4e4..6d83f963f0a 100644
> --- a/src/mesa/state_tracker/st_atom_sampler.c
> +++ b/src/mesa/state_tracker/st_atom_sampler.c
> @@ -36,20 +36,21 @@
> #include "main/mtypes.h"
> #include "main/glformats.h"
> #include "main/samplerobj.h"
> #include "main/teximage.h"
> #include "main/texobj.h"
>
> #include "st_context.h"
> #include "st_cb_texture.h"
> #include "st_format.h"
> #include "st_atom.h"
> +#include "st_sampler_view.h"
> #include "st_texture.h"
> #include "pipe/p_context.h"
> #include "pipe/p_defines.h"
>
> #include "cso_cache/cso_context.h"
>
> #include "util/u_format.h"
>
>
> /**
> @@ -157,40 +158,32 @@ st_convert_sampler(const struct st_context *st,
> (sampler->wrap_s | sampler->wrap_t | sampler->wrap_r) & 0x1 &&
> (msamp->BorderColor.ui[0] ||
> msamp->BorderColor.ui[1] ||
> msamp->BorderColor.ui[2] ||
> msamp->BorderColor.ui[3])) {
> const GLboolean is_integer = texobj->_IsIntegerFormat;
> GLenum texBaseFormat = _mesa_base_tex_image(texobj)->_BaseFormat;
>
> if (st->apply_texture_swizzle_to_border_color) {
> const struct st_texture_object *stobj = st_texture_object_const(texobj);
> - const struct pipe_sampler_view *sv = NULL;
> -
> - /* Just search for the first used view. We can do this because the
> - swizzle is per-texture, not per context. */
> /* XXX: clean that up to not use the sampler view at all */
> - for (unsigned i = 0; i < stobj->num_sampler_views; ++i) {
> - if (stobj->sampler_views[i].view) {
> - sv = stobj->sampler_views[i].view;
> - break;
> - }
> - }
> + const struct st_sampler_view *sv = st_texture_get_current_sampler_view(st, stobj);
>
> if (sv) {
> + struct pipe_sampler_view *view = sv->view;
> union pipe_color_union tmp;
> const unsigned char swz[4] =
> {
> - sv->swizzle_r,
> - sv->swizzle_g,
> - sv->swizzle_b,
> - sv->swizzle_a,
> + view->swizzle_r,
> + view->swizzle_g,
> + view->swizzle_b,
> + view->swizzle_a,
> };
>
> st_translate_color(&msamp->BorderColor, &tmp,
> texBaseFormat, is_integer);
>
> util_format_apply_color_swizzle(&sampler->border_color,
> &tmp, swz, is_integer);
> } else {
> st_translate_color(&msamp->BorderColor,
> &sampler->border_color,
> diff --git a/src/mesa/state_tracker/st_cb_texture.c b/src/mesa/state_tracker/st_cb_texture.c
> index 3b7a3b5e985..7766273381b 100644
> --- a/src/mesa/state_tracker/st_cb_texture.c
> +++ b/src/mesa/state_tracker/st_cb_texture.c
> @@ -144,40 +144,52 @@ st_DeleteTextureImage(struct gl_context * ctx, struct gl_texture_image *img)
> /* nothing special (yet) for st_texture_image */
> _mesa_delete_texture_image(ctx, img);
> }
>
>
> /** called via ctx->Driver.NewTextureObject() */
> static struct gl_texture_object *
> st_NewTextureObject(struct gl_context * ctx, GLuint name, GLenum target)
> {
> struct st_texture_object *obj = ST_CALLOC_STRUCT(st_texture_object);
> + if (!obj)
> + return NULL;
> +
> + /* Pre-allocate a sampler views container to save a branch in the fast path. */
> + obj->sampler_views = calloc(1, sizeof(struct st_sampler_views) + sizeof(struct st_sampler_view));
> + if (!obj->sampler_views) {
> + free(obj);
> + return NULL;
> + }
> + obj->sampler_views->max = 1;
>
> DBG("%s\n", __func__);
> _mesa_initialize_texture_object(ctx, &obj->base, name, target);
>
> + simple_mtx_init(&obj->validate_mutex, mtx_plain);
> obj->needs_validation = true;
>
> return &obj->base;
> }
>
> /** called via ctx->Driver.DeleteTextureObject() */
> static void
> st_DeleteTextureObject(struct gl_context *ctx,
> struct gl_texture_object *texObj)
> {
> struct st_context *st = st_context(ctx);
> struct st_texture_object *stObj = st_texture_object(texObj);
>
> pipe_resource_reference(&stObj->pt, NULL);
> st_texture_release_all_sampler_views(st, stObj);
> st_texture_free_sampler_views(stObj);
> + simple_mtx_destroy(&stObj->validate_mutex);
> _mesa_delete_texture_object(ctx, texObj);
> }
>
>
> /** called via ctx->Driver.FreeTextureImageBuffer() */
> static void
> st_FreeTextureImageBuffer(struct gl_context *ctx,
> struct gl_texture_image *texImage)
> {
> struct st_context *st = st_context(ctx);
> diff --git a/src/mesa/state_tracker/st_sampler_view.c b/src/mesa/state_tracker/st_sampler_view.c
> index 892725671d2..b737011d501 100644
> --- a/src/mesa/state_tracker/st_sampler_view.c
> +++ b/src/mesa/state_tracker/st_sampler_view.c
> @@ -36,104 +36,216 @@
>
> #include "st_context.h"
> #include "st_sampler_view.h"
> #include "st_texture.h"
> #include "st_format.h"
> #include "st_cb_bufferobjects.h"
> #include "st_cb_texture.h"
>
>
> /**
> - * Try to find a matching sampler view for the given context.
> - * If none is found an empty slot is initialized with a
> - * template and returned instead.
> + * Set the given view as the current context's view for the texture.
> + *
> + * Overwrites any pre-existing view of the context.
> + *
> + * Takes ownership of the view (i.e., stores the view without incrementing the
> + * reference count).
> + *
> + * \return the view, or NULL on error. In case of error, the reference to the
> + * view is released.
> */
> -static struct st_sampler_view *
> -st_texture_get_sampler_view(struct st_context *st,
> - struct st_texture_object *stObj)
> +static struct pipe_sampler_view *
> +st_texture_set_sampler_view(struct st_context *st,
> + struct st_texture_object *stObj,
> + struct pipe_sampler_view *view,
> + bool glsl130_or_later, bool srgb_skip_decode)
> {
> + struct st_sampler_views *views;
> struct st_sampler_view *free = NULL;
> + struct st_sampler_view *sv;
> GLuint i;
>
> - for (i = 0; i < stObj->num_sampler_views; ++i) {
> - struct st_sampler_view *sv = &stObj->sampler_views[i];
> + simple_mtx_lock(&stObj->validate_mutex);
> + views = stObj->sampler_views;
> +
> + for (i = 0; i < views->count; ++i) {
> + sv = &views->views[i];
> +
> /* Is the array entry used ? */
> if (sv->view) {
> /* check if the context matches */
> if (sv->view->context == st->pipe) {
> - return sv;
> + pipe_sampler_view_release(st->pipe, &sv->view);
> + goto found;
> }
> } else {
> /* Found a free slot, remember that */
> free = sv;
> }
> }
>
> /* Couldn't find a slot for our context, create a new one */
> + if (free) {
> + sv = free;
> + } else {
> + if (views->count >= views->max) {
> + /* Allocate a larger container. */
> + unsigned new_max = 2 * views->max;
> + unsigned new_size = sizeof(*views) + new_max * sizeof(views->views[0]);
> +
> + if (new_max < views->max ||
> + new_max > (UINT_MAX - sizeof(*views)) / sizeof(views->views[0])) {
> + pipe_sampler_view_release(st->pipe, &view);
> + goto out;
> + }
> +
> + struct st_sampler_views *new_views = malloc(new_size);
> + if (!new_views) {
> + pipe_sampler_view_release(st->pipe, &view);
> + goto out;
> + }
> +
> + new_views->count = views->count;
> + new_views->max = new_max;
> + memcpy(&new_views->views[0], &views->views[0],
> + views->count * sizeof(views->views[0]));
> +
> + /* Initialize the pipe_sampler_view pointers to zero so that we don't
> + * have to worry about racing against readers when incrementing
> + * views->count.
> + */
> + memset(&new_views->views[views->count], 0,
> + (new_max - views->count) * sizeof(views->views[0]));
> +
> + /* Use memory release semantics to ensure that concurrent readers will
> + * get the correct contents of the new container.
> + *
> + * Also, the write should be atomic, but that's guaranteed anyway on
> + * all supported platforms.
> + */
> + p_atomic_set(&stObj->sampler_views, new_views);
> +
> + /* We keep the old container around until the texture object is
> + * deleted, because another thread may still be reading from it. We
> + * double the size of the container each time, so we end up with
> + * at most twice the total memory allocation.
> + */
> + views->next = stObj->sampler_views_old;
> + stObj->sampler_views_old = views;
> +
> + views = new_views;
> + }
> +
> + sv = &views->views[views->count];
>
> - if (!free) {
> - /* Haven't even found a free one, resize the array */
> - unsigned new_size = (stObj->num_sampler_views + 1) *
> - sizeof(struct st_sampler_view);
> - stObj->sampler_views = realloc(stObj->sampler_views, new_size);
> - free = &stObj->sampler_views[stObj->num_sampler_views++];
> - free->view = NULL;
> + /* Since modification is guarded by the lock, only the write part of the
> + * increment has to be atomic, and that's already guaranteed on all
> + * supported platforms without using an atomic intrinsic.
> + */
> + views->count++;
> }
>
> - assert(free->view == NULL);
> +found:
> + assert(sv->view == NULL);
> +
> + sv->glsl130_or_later = glsl130_or_later;
> + sv->srgb_skip_decode = srgb_skip_decode;
> + sv->view = view;
> +
> +out:
> + simple_mtx_unlock(&stObj->validate_mutex);
> + return view;
> +}
> +
> +
> +/**
> + * Return the most-recently validated sampler view for the texture \p stObj
> + * in the given context, if any.
> + *
> + * Performs no additional validation.
> + */
> +const struct st_sampler_view *
> +st_texture_get_current_sampler_view(const struct st_context *st,
> + const struct st_texture_object *stObj)
> +{
> + const struct st_sampler_views *views = p_atomic_read(&stObj->sampler_views);
> +
> + for (unsigned i = 0; i < views->count; ++i) {
> + const struct st_sampler_view *sv = &views->views[i];
> + if (sv->view && sv->view->context == st->pipe)
> + return sv;
> + }
>
> - return free;
> + return NULL;
> }
>
>
> /**
> * For the given texture object, release any sampler views which belong
> * to the calling context.
> */
> void
> st_texture_release_sampler_view(struct st_context *st,
> struct st_texture_object *stObj)
> {
> GLuint i;
>
> - for (i = 0; i < stObj->num_sampler_views; ++i) {
> - struct pipe_sampler_view **sv = &stObj->sampler_views[i].view;
> + simple_mtx_lock(&stObj->validate_mutex);
> + struct st_sampler_views *views = stObj->sampler_views;
> + for (i = 0; i < views->count; ++i) {
> + struct pipe_sampler_view **sv = &views->views[i].view;
>
> if (*sv && (*sv)->context == st->pipe) {
> pipe_sampler_view_reference(sv, NULL);
> break;
> }
> }
> + simple_mtx_unlock(&stObj->validate_mutex);
> }
>
>
> /**
> * Release all sampler views attached to the given texture object, regardless
> * of the context.
> */
> void
> st_texture_release_all_sampler_views(struct st_context *st,
> struct st_texture_object *stObj)
> {
> GLuint i;
>
> - for (i = 0; i < stObj->num_sampler_views; ++i)
> - pipe_sampler_view_release(st->pipe, &stObj->sampler_views[i].view);
> + /* TODO: This happens while a texture is deleted, because the Driver API
> + * is asymmetric: the driver allocates the texture object memory, but
> + * mesa/main frees it.
> + */
> + if (!stObj->sampler_views)
> + return;
> +
> + simple_mtx_lock(&stObj->validate_mutex);
> + struct st_sampler_views *views = stObj->sampler_views;
> + for (i = 0; i < views->count; ++i)
> + pipe_sampler_view_release(st->pipe, &views->views[i].view);
> + simple_mtx_unlock(&stObj->validate_mutex);
> }
>
>
> void
> st_texture_free_sampler_views(struct st_texture_object *stObj)
> {
> free(stObj->sampler_views);
> stObj->sampler_views = NULL;
> - stObj->num_sampler_views = 0;
> +
> + while (stObj->sampler_views_old) {
> + struct st_sampler_views *views = stObj->sampler_views_old;
> + stObj->sampler_views_old = views->next;
> + free(views);
> + }
> }
>
>
> /**
> * Return swizzle1(swizzle2)
> */
> static unsigned
> swizzle_swizzle(unsigned swizzle1, unsigned swizzle2)
> {
> unsigned i, swz[4];
> @@ -403,115 +515,117 @@ st_create_texture_sampler_view_from_stobj(struct st_context *st,
> }
>
>
> struct pipe_sampler_view *
> st_get_texture_sampler_view_from_stobj(struct st_context *st,
> struct st_texture_object *stObj,
> const struct gl_sampler_object *samp,
> bool glsl130_or_later,
> bool ignore_srgb_decode)
> {
> - struct st_sampler_view *sv;
> - struct pipe_sampler_view *view;
> + const struct st_sampler_view *sv;
> bool srgb_skip_decode = false;
>
> - sv = st_texture_get_sampler_view(st, stObj);
> - view = sv->view;
> -
> if (!ignore_srgb_decode && samp->sRGBDecode == GL_SKIP_DECODE_EXT)
> srgb_skip_decode = true;
>
> - if (view &&
> + sv = st_texture_get_current_sampler_view(st, stObj);
> +
> + if (sv &&
> sv->glsl130_or_later == glsl130_or_later &&
> sv->srgb_skip_decode == srgb_skip_decode) {
> /* Debug check: make sure that the sampler view's parameters are
> * what they're supposed to be.
> */
> - MAYBE_UNUSED struct pipe_sampler_view *view = sv->view;
> + struct pipe_sampler_view *view = sv->view;
> assert(stObj->pt == view->texture);
> assert(!check_sampler_swizzle(st, stObj, view, glsl130_or_later));
> assert(get_sampler_view_format(st, stObj, srgb_skip_decode) == view->format);
> assert(gl_target_to_pipe(stObj->base.Target) == view->target);
> assert(stObj->level_override ||
> stObj->base.MinLevel + stObj->base.BaseLevel == view->u.tex.first_level);
> assert(stObj->level_override || last_level(stObj) == view->u.tex.last_level);
> assert(stObj->layer_override || stObj->base.MinLayer == view->u.tex.first_layer);
> assert(stObj->layer_override || last_layer(stObj) == view->u.tex.last_layer);
> assert(!stObj->layer_override ||
> (stObj->layer_override == view->u.tex.first_layer &&
> stObj->layer_override == view->u.tex.last_layer));
> + return view;
> }
> - else {
> - /* create new sampler view */
> - enum pipe_format format = get_sampler_view_format(st, stObj, srgb_skip_decode);
> -
> - sv->glsl130_or_later = glsl130_or_later;
> - sv->srgb_skip_decode = srgb_skip_decode;
>
> - pipe_sampler_view_release(st->pipe, &sv->view);
> - view = sv->view =
> + /* create new sampler view */
> + enum pipe_format format = get_sampler_view_format(st, stObj, srgb_skip_decode);
> + struct pipe_sampler_view *view =
> st_create_texture_sampler_view_from_stobj(st, stObj, format, glsl130_or_later);
> - }
> +
> + view = st_texture_set_sampler_view(st, stObj, view, glsl130_or_later, srgb_skip_decode);
>
> return view;
> }
>
>
> struct pipe_sampler_view *
> st_get_buffer_sampler_view_from_stobj(struct st_context *st,
> struct st_texture_object *stObj)
> {
> - struct st_sampler_view *sv;
> + const struct st_sampler_view *sv;
> struct st_buffer_object *stBuf =
> st_buffer_object(stObj->base.BufferObject);
>
> if (!stBuf || !stBuf->buffer)
> return NULL;
>
> - sv = st_texture_get_sampler_view(st, stObj);
> + sv = st_texture_get_current_sampler_view(st, stObj);
>
> struct pipe_resource *buf = stBuf->buffer;
> - struct pipe_sampler_view *view = sv->view;
>
> - if (view && view->texture == buf) {
> - /* Debug check: make sure that the sampler view's parameters are
> - * what they're supposed to be.
> - */
> - assert(st_mesa_format_to_pipe_format(st, stObj->base._BufferObjectFormat)
> + if (sv) {
> + struct pipe_sampler_view *view = sv->view;
> +
> + if (view->texture == buf) {
> + /* Debug check: make sure that the sampler view's parameters are
> + * what they're supposed to be.
> + */
> + assert(st_mesa_format_to_pipe_format(st, stObj->base._BufferObjectFormat)
> == view->format);
> - assert(view->target == PIPE_BUFFER);
> - unsigned base = stObj->base.BufferOffset;
> - MAYBE_UNUSED unsigned size = MIN2(buf->width0 - base,
> + assert(view->target == PIPE_BUFFER);
> + unsigned base = stObj->base.BufferOffset;
> + MAYBE_UNUSED unsigned size = MIN2(buf->width0 - base,
> (unsigned) stObj->base.BufferSize);
> - assert(view->u.buf.offset == base);
> - assert(view->u.buf.size == size);
> - } else {
> - unsigned base = stObj->base.BufferOffset;
> + assert(view->u.buf.offset == base);
> + assert(view->u.buf.size == size);
> + return view;
> + }
> + }
>
> - if (base >= buf->width0)
> - return NULL;
> + unsigned base = stObj->base.BufferOffset;
>
> - unsigned size = buf->width0 - base;
> - size = MIN2(size, (unsigned)stObj->base.BufferSize);
> - if (!size)
> - return NULL;
> + if (base >= buf->width0)
> + return NULL;
> +
> + unsigned size = buf->width0 - base;
> + size = MIN2(size, (unsigned)stObj->base.BufferSize);
> + if (!size)
> + return NULL;
> +
> + /* Create a new sampler view. There is no need to clear the entire
> + * structure (consider CPU overhead).
> + */
> + struct pipe_sampler_view templ;
> +
> + templ.format =
> + st_mesa_format_to_pipe_format(st, stObj->base._BufferObjectFormat);
> + templ.target = PIPE_BUFFER;
> + templ.swizzle_r = PIPE_SWIZZLE_X;
> + templ.swizzle_g = PIPE_SWIZZLE_Y;
> + templ.swizzle_b = PIPE_SWIZZLE_Z;
> + templ.swizzle_a = PIPE_SWIZZLE_W;
> + templ.u.buf.offset = base;
> + templ.u.buf.size = size;
> +
> + struct pipe_sampler_view *view =
> + st->pipe->create_sampler_view(st->pipe, buf, &templ);
> +
> + view = st_texture_set_sampler_view(st, stObj, view, false, false);
>
> - /* Create a new sampler view. There is no need to clear the entire
> - * structure (consider CPU overhead).
> - */
> - struct pipe_sampler_view templ;
> -
> - templ.format =
> - st_mesa_format_to_pipe_format(st, stObj->base._BufferObjectFormat);
> - templ.target = PIPE_BUFFER;
> - templ.swizzle_r = PIPE_SWIZZLE_X;
> - templ.swizzle_g = PIPE_SWIZZLE_Y;
> - templ.swizzle_b = PIPE_SWIZZLE_Z;
> - templ.swizzle_a = PIPE_SWIZZLE_W;
> - templ.u.buf.offset = base;
> - templ.u.buf.size = size;
> -
> - pipe_sampler_view_release(st->pipe, &sv->view);
> - view = sv->view = st->pipe->create_sampler_view(st->pipe, buf, &templ);
> - }
> return view;
> }
> diff --git a/src/mesa/state_tracker/st_sampler_view.h b/src/mesa/state_tracker/st_sampler_view.h
> index cf46513f1b4..47c100df647 100644
> --- a/src/mesa/state_tracker/st_sampler_view.h
> +++ b/src/mesa/state_tracker/st_sampler_view.h
> @@ -61,20 +61,23 @@ extern void
> st_texture_release_sampler_view(struct st_context *st,
> struct st_texture_object *stObj);
>
> extern void
> st_texture_release_all_sampler_views(struct st_context *st,
> struct st_texture_object *stObj);
>
> void
> st_texture_free_sampler_views(struct st_texture_object *stObj);
>
> +const struct st_sampler_view *
> +st_texture_get_current_sampler_view(const struct st_context *st,
> + const struct st_texture_object *stObj);
>
> struct pipe_sampler_view *
> st_get_texture_sampler_view_from_stobj(struct st_context *st,
> struct st_texture_object *stObj,
> const struct gl_sampler_object *samp,
> bool glsl130_or_later,
> bool ignore_srgb_decode);
>
> struct pipe_sampler_view *
> st_get_buffer_sampler_view_from_stobj(struct st_context *st,
> diff --git a/src/mesa/state_tracker/st_texture.h b/src/mesa/state_tracker/st_texture.h
> index 8b549b86085..c10a2753104 100644
> --- a/src/mesa/state_tracker/st_texture.h
> +++ b/src/mesa/state_tracker/st_texture.h
> @@ -24,20 +24,21 @@
> * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
> *
> **************************************************************************/
>
> #ifndef ST_TEXTURE_H
> #define ST_TEXTURE_H
>
>
> #include "pipe/p_context.h"
> #include "util/u_sampler.h"
> +#include "util/simple_mtx.h"
>
> #include "main/mtypes.h"
>
>
> struct pipe_resource;
>
>
> struct st_texture_image_transfer {
> struct pipe_transfer *transfer;
>
> @@ -55,20 +56,30 @@ struct st_sampler_view {
> struct pipe_sampler_view *view;
>
> /** The glsl version of the shader seen during validation */
> bool glsl130_or_later;
> /** Derived from the sampler's sRGBDecode state during validation */
> bool srgb_skip_decode;
> };
>
>
> /**
> + * Container for per-context sampler views of a texture.
> + */
> +struct st_sampler_views {
> + struct st_sampler_views *next;
> + uint32_t max;
> + uint32_t count;
> + struct st_sampler_view views[0];
> +};
> +
> +/**
> * Subclass of gl_texure_image.
> */
> struct st_texture_image
> {
> struct gl_texture_image base;
>
> /* If stImage->pt != NULL, image data is stored here.
> * Else there is no image data.
> */
> struct pipe_resource *pt;
> @@ -98,27 +109,48 @@ struct st_texture_object
> GLuint lastLevel;
>
> unsigned int validated_first_level;
> unsigned int validated_last_level;
>
> /* On validation any active images held in main memory or in other
> * textures will be copied to this texture and the old storage freed.
> */
> struct pipe_resource *pt;
>
> - /* Number of views in sampler_views array */
> - GLuint num_sampler_views;
> + /* Protect modifications of the sampler_views array */
> + simple_mtx_t validate_mutex;
>
> - /* Array of sampler views (one per context) attached to this texture
> + /* Container of sampler views (one per context) attached to this texture
> * object. Created lazily on first binding in context.
> + *
> + * Purely read-only accesses to the current context's own sampler view
> + * require no locking. Another thread may simultaneously replace the
> + * container object in order to grow the array, but the old container will
> + * be kept alive.
> + *
> + * Writing to the container (even for modifying the current context's own
> + * sampler view) always requires taking the validate_mutex to protect against
> + * concurrent container switches.
> + *
> + * NULL'ing another context's sampler view is allowed only while
> + * implementing an API call that modifies the texture: an application which
> + * calls those while simultaneously reading the texture in another context
> + * invokes undefined behavior. (TODO: a dubious violation of this rule is
> + * st_finalize_texture, which is a lazy operation that corresponds to a
> + * texture modification.)
> + */
> + struct st_sampler_views *sampler_views;
> +
> + /* Old sampler views container objects that have not been freed yet because
> + * other threads/contexts may still be reading from them.
> */
> - struct st_sampler_view *sampler_views;
> + struct st_sampler_views *sampler_views_old;
>
> /* True if this texture comes from the window system. Such a texture
> * cannot be reallocated and the format can only be changed with a sampler
> * view or a surface.
> */
> GLboolean surface_based;
>
> /* If surface_based is true, this format should be used for all sampler
> * views and surfaces instead of pt->format.
> */
> --
> 2.11.0
>
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