diff options
| -rw-r--r-- | src/modules/snow/snow.c | 47 |
1 files changed, 38 insertions, 9 deletions
diff --git a/src/modules/snow/snow.c b/src/modules/snow/snow.c index 8968e47..3e6331a 100644 --- a/src/modules/snow/snow.c +++ b/src/modules/snow/snow.c @@ -9,13 +9,37 @@ /* This implements white noise / snow just using rand() */ -/* To avoid the contention around rand() I'm just using rand_r() - * in an entirely racy fashion with a single seed from the threaded - * render_fragment(). It should really be per-cpu but the module - * api doesn't currently send down a cpu identifier to the render - * function, so TODO in the future add that. - */ -static int snow_seed; +typedef union snow_seed_t { + char __padding[256]; /* prevent seeds sharing a cache-line */ + int seed; +} snow_seed_t; + +typedef struct snow_context_t { + int foo; /* make the compiler happy */ + snow_seed_t seeds[]; +} snow_context_t; + + +static void * snow_create_context(unsigned n_cpus) +{ + snow_context_t *ctxt; + + ctxt = calloc(1, sizeof(snow_context_t) + n_cpus * sizeof(snow_seed_t)); + if (!ctxt) + return NULL; + + for (unsigned i = 0; i < n_cpus; i++) + ctxt->seeds[i].seed = rand(); + + return ctxt; +} + + +static void snow_destroy_context(void *context) +{ + free(context); +} + static int snow_fragmenter(void *context, const fb_fragment_t *fragment, unsigned number, fb_fragment_t *res_fragment) { @@ -31,9 +55,12 @@ static void snow_prepare_frame(void *context, unsigned n_cpus, fb_fragment_t *fr static void snow_render_fragment(void *context, unsigned cpu, fb_fragment_t *fragment) { + snow_context_t *ctxt = context; + int *seed = &ctxt->seeds[cpu].seed; + for (unsigned y = fragment->y; y < fragment->y + fragment->height; y++) { for (unsigned x = fragment->x; x < fragment->x + fragment->width; x++) { - uint32_t pixel = rand_r(&snow_seed) % 256; + uint32_t pixel = rand_r(seed) % 256; fb_fragment_put_pixel_unchecked(fragment, x, y, pixel << 16 | pixel << 8 | pixel); } @@ -42,10 +69,12 @@ static void snow_render_fragment(void *context, unsigned cpu, fb_fragment_t *fra rototiller_module_t snow_module = { + .create_context = snow_create_context, + .destroy_context = snow_destroy_context, .prepare_frame = snow_prepare_frame, .render_fragment = snow_render_fragment, .name = "snow", - .description = "TV snow / white noise", + .description = "TV snow / white noise (threaded)", .author = "Vito Caputo <vcaputo@pengaru.com>", .license = "GPLv2", }; |