[Mesa-dev] [PATCH v3 4/4] glthread/gallium: require safe_glthread to start glthread

[Gregory Hainaut]

Print an error message for the user if the requirement isn't met, or
we're not thread safe.

v2: based on Nicolai feedbacks
Check the DRI extension version
v3: based on Emil feedbacks
improve commit and error messages.
use backgroundCallable variable to improve readability

Signed-off-by: Gregory Hainaut <gregory.hainaut at gmail.com>
---
 src/gallium/state_trackers/dri/dri_context.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/src/gallium/state_trackers/dri/dri_context.c b/src/gallium/state_trackers/dri/dri_context.c
index 92d79849c4..8cbab5359f 100644
--- a/src/gallium/state_trackers/dri/dri_context.c
+++ b/src/gallium/state_trackers/dri/dri_context.c
@@ -51,20 +51,22 @@ dri_create_context(gl_api api, const struct gl_config * visual,
 {
    __DRIscreen *sPriv = cPriv->driScreenPriv;
    struct dri_screen *screen = dri_screen(sPriv);
    struct st_api *stapi = screen->st_api;
    struct dri_context *ctx = NULL;
    struct st_context_iface *st_share = NULL;
    struct st_context_attribs attribs;
    enum st_context_error ctx_err = 0;
    unsigned allowed_flags = __DRI_CTX_FLAG_DEBUG |
                             __DRI_CTX_FLAG_FORWARD_COMPATIBLE;
+   const __DRIbackgroundCallableExtension *backgroundCallable =
+      screen->sPriv->dri2.backgroundCallable;
 
    if (screen->has_reset_status_query)
       allowed_flags |= __DRI_CTX_FLAG_ROBUST_BUFFER_ACCESS;
 
    if (flags & ~allowed_flags) {
       *error = __DRI_CTX_ERROR_UNKNOWN_FLAG;
       goto fail;
    }
 
    if (!screen->has_reset_status_query && notify_reset) {
@@ -151,24 +153,35 @@ dri_create_context(gl_api api, const struct gl_config * visual,
    ctx->st->st_manager_private = (void *) ctx;
    ctx->stapi = stapi;
 
    if (ctx->st->cso_context) {
       ctx->pp = pp_init(ctx->st->pipe, screen->pp_enabled, ctx->st->cso_context);
       ctx->hud = hud_create(ctx->st->pipe, ctx->st->cso_context);
    }
 
    /* Do this last. */
    if (ctx->st->start_thread &&
-       /* the driver loader must implement this */
-       screen->sPriv->dri2.backgroundCallable &&
-       driQueryOptionb(&screen->optionCache, "mesa_glthread"))
-      ctx->st->start_thread(ctx->st);
+         driQueryOptionb(&screen->optionCache, "mesa_glthread")) {
+
+      if (backgroundCallable && backgroundCallable->base.version >= 2 &&
+            driQueryOptionb(&screen->optionCache, "mesa_glthread")) {
+
+         if (backgroundCallable->isThreadSafe(cPriv->loaderPrivate))
+            ctx->st->start_thread(ctx->st);
+         else
+            fprintf(stderr, "dri_create_context: glthread isn't thread safe "
+                  "- missing call XInitThreads\n");
+      } else {
+         fprintf(stderr, "dri_create_context: requested glthread but driver "
+               "is missing backgroundCallable V2 extension\n");
+      }
+   }
 
    *error = __DRI_CTX_ERROR_SUCCESS;
    return GL_TRUE;
 
  fail:
    if (ctx && ctx->st)
       ctx->st->destroy(ctx->st);
 
    free(ctx);
    return GL_FALSE;
-- 
2.11.0