Quoting Michel Thierry (2017-05-22 18:46:24)
> + /* try engine reset first, and continue if fails */
/* Please use sentences when convenient. It looks much neater that way. */
> + if (intel_has_reset_engine(dev_priv)) {
> + struct intel_engine_cs *engine;
> + unsigned int tmp;
> +
> + /* protect against concurrent reset attempts */
> + if (test_and_set_bit(I915_RESET_ENGINE_IN_PROGRESS,
> + &dev_priv->gpu_error.flags))
> + goto out;
> +
> + for_each_engine_masked(engine, dev_priv, engine_mask, tmp) {
> + if (i915_reset_engine(engine) == 0)
> + engine_mask &= ~intel_engine_flag(engine);
> + }
> +
> + /* clear unconditionally, full reset won't care about it */
> + clear_bit(I915_RESET_ENGINE_IN_PROGRESS,
> + &dev_priv->gpu_error.flags);
> +
> + if (!engine_mask)
> + goto out;
> + }
> +
> + /* full reset needs the mutex, stop any other user trying to do so */
> if (test_and_set_bit(I915_RESET_BACKOFF,
> &dev_priv->gpu_error.flags))
We have a big gaping hole here in coordination between a global reset
and per-engine resets.
I think you want to do something like:
if (intel_has_engine_reset()) {
for_each_engine_mask() {
if (test_and_set_bit(I915_RESET_ENGINE + engine->id))
continue;
if (i915_reset_engine() == 0)
engine_mask &= ~engine->mask;
clear_bit(I915_RESET_ENGINE + engine->id);
wake_up_bit(I915_RESET_ENGINE + engine->id);
}
}
if (!engine_mask)
goto out;
if (test_and_set_bit(I915_RESET_BACKOFF))
goto out;
for_each_engine() {
wait_on_bit(I915_RESET_ENGINE + engine->id);
set_bit(I915_RESET_ENGINE);
}
...do global reset...
for_each_engine() {
clear_bit(I915_RESET_ENGINE);
}
The idea is that any per-engine reset that comes in whilst global is in
progress can skip, and that the global waits for any per-engine reset to
finish before clobbering state. The window in which global reset
completes and a new hang is detected before we clear the bits, I am
judiciously ignoring. Also this should allow us to perform parallel
resets between engines. (Now that's a selling point!)
-Chris
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