Quoting Chris Wilson (2018-03-06 10:41:41)
> static void *thread(void *arg)
> {
> + static const char acquire_error[] = "acquire";
> + static const char release_error[] = "release";
> +
> struct thread *t = arg;
> - uint32_t *forcewake_mt = (uint32_t *)((char *)t->mmio + FORCEWAKE_MT);
> - uint32_t bit = 1 << t->bit;
> + const uint32_t bit = 1 << t->bit;
> + volatile uint32_t *forcewake_mt = t->forcewake_mt;
> + void *result = NULL;
> +
> + while (!result && !READ_ONCE(t->done)) {
> + /*
> + * The HW is fubar; concurrent mmio access to even
> + * the FORCEWAKE_MT results in a machine lockup, nullifying
> + * the entire purpose of FORCEWAKE_MT... Sigh.
> + */
> + pthread_mutex_lock(t->lock);
>
> - while (1) {
> *forcewake_mt = bit << 16 | bit;
> - igt_assert(*forcewake_mt & bit);
> + if (!igt_wait(*forcewake_mt & bit, 50, 1))
> + result = (void *)acquire_error;
> +
Imagine there was
pthread_mutex_unlock(t->lock);
usleep(10000);
pthread_mutex_lock(t->lock);
here.
> *forcewake_mt = bit << 16;
> - igt_assert((*forcewake_mt & bit) == 0);
> + if (!igt_wait((*forcewake_mt & bit) == 0, 50, 1))
> + result = (void *)release_error;
> +
> + pthread_mutex_unlock(t->lock);
> }
-Chris
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