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output: rejigger attach/clear for back buffer

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In wlr_output_attach_render(), stop setting
wlr_output.pending.buffer. This removes one footgun: using the
wlr_buffer at that stage is invalid, because rendering operations
haven't been flushed to the GPU yet. We need to wait until
output_clear_back_buffer() for the wlr_buffer to be used safely.

Instead, set wlr_output.pending.buffer in wlr_output_test() and
wlr_output_commit().

Additionally, move the output_clear_back_buffer() from
wlr_output_commit_state() to wlr_output_commit(). This reduces the
number of calls in the failure path.
This commit is contained in:
Simon Ser 2022-09-18 16:29:36 +02:00 • committed by Simon Zeni
parent 0213da60bb
commit 0556aa0c59
2 changed files with 22 additions and 22 deletions
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37
types/output/output.c
View file

@ -700,7 +700,15 @@ bool wlr_output_test_state(struct wlr_output *output,
} }
bool wlr_output_test(struct wlr_output *output) { bool wlr_output_test(struct wlr_output *output) {
return wlr_output_test_state(output, &output->pending); struct wlr_output_state state = output->pending;
if (output->back_buffer != NULL) {
assert((state.committed & WLR_OUTPUT_STATE_BUFFER) == 0);
state.committed |= WLR_OUTPUT_STATE_BUFFER;
state.buffer = output->back_buffer;
}
return wlr_output_test_state(output, &state);
} }
bool wlr_output_commit_state(struct wlr_output *output, bool wlr_output_commit_state(struct wlr_output *output,
@ -714,21 +722,17 @@ bool wlr_output_commit_state(struct wlr_output *output,
if (!output_basic_test(output, &pending)) { if (!output_basic_test(output, &pending)) {
wlr_log(WLR_ERROR, "Basic output test failed for %s", output->name); wlr_log(WLR_ERROR, "Basic output test failed for %s", output->name);
output_clear_back_buffer(output);
return false; return false;
} }
bool new_back_buffer = false; bool new_back_buffer = false;
if (!output_ensure_buffer(output, &pending, &new_back_buffer)) { if (!output_ensure_buffer(output, &pending, &new_back_buffer)) {
output_clear_back_buffer(output);
return false; return false;
} }
if (new_back_buffer) { if (new_back_buffer) {
assert((pending.committed & WLR_OUTPUT_STATE_BUFFER) == 0); assert((pending.committed & WLR_OUTPUT_STATE_BUFFER) == 0);
pending.committed |= WLR_OUTPUT_STATE_BUFFER; output_state_attach_buffer(&pending, output->back_buffer);
// Lock the buffer to ensure it stays valid past the output_clear_back_buffer(output);
// output_clear_back_buffer() call below.
pending.buffer = wlr_buffer_lock(output->back_buffer);
} }
if ((pending.committed & WLR_OUTPUT_STATE_BUFFER) && if ((pending.committed & WLR_OUTPUT_STATE_BUFFER) &&
@ -747,15 +751,6 @@ bool wlr_output_commit_state(struct wlr_output *output,
}; };
wl_signal_emit_mutable(&output->events.precommit, &pre_event); wl_signal_emit_mutable(&output->events.precommit, &pre_event);
// output_clear_back_buffer detaches the buffer from the renderer. This is
// important to do before calling impl->commit(), because this marks an
// implicit rendering synchronization point. The backend needs it to avoid
// displaying a buffer when asynchronous GPU work isn't finished.
if ((pending.committed & WLR_OUTPUT_STATE_BUFFER) &&
output->back_buffer != NULL) {
output_clear_back_buffer(output);
}
if (!output->impl->commit(output, &pending)) { if (!output->impl->commit(output, &pending)) {
if (new_back_buffer) { if (new_back_buffer) {
wlr_buffer_unlock(pending.buffer); wlr_buffer_unlock(pending.buffer);
@ -845,6 +840,16 @@ bool wlr_output_commit(struct wlr_output *output) {
// Make sure the pending state is cleared before the output is committed // Make sure the pending state is cleared before the output is committed
struct wlr_output_state state = {0}; struct wlr_output_state state = {0};
output_state_move(&state, &output->pending); output_state_move(&state, &output->pending);
// output_clear_back_buffer detaches the buffer from the renderer. This is
// important to do before calling impl->commit(), because this marks an
// implicit rendering synchronization point. The backend needs it to avoid
// displaying a buffer when asynchronous GPU work isn't finished.
if (output->back_buffer != NULL) {
output_state_attach_buffer(&state, output->back_buffer);
output_clear_back_buffer(output);
}
bool ok = wlr_output_commit_state(output, &state); bool ok = wlr_output_commit_state(output, &state);
output_state_finish(&state); output_state_finish(&state);
return ok; return ok;

7
types/output/render.c
View file

@ -142,12 +142,7 @@ void output_clear_back_buffer(struct wlr_output *output) {
} }
bool wlr_output_attach_render(struct wlr_output *output, int *buffer_age) { bool wlr_output_attach_render(struct wlr_output *output, int *buffer_age) {
struct wlr_output_state *state = &output->pending; return output_attach_back_buffer(output, &output->pending, buffer_age);
if (!output_attach_back_buffer(output, state, buffer_age)) {
return false;
}
output_state_attach_buffer(state, output->back_buffer);
return true;
} }
static bool output_attach_empty_back_buffer(struct wlr_output *output, static bool output_attach_empty_back_buffer(struct wlr_output *output,