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x11bridge: tolerate redundant GEM close for multi-plane DRI3 buffers #231

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x11bridge: tolerate redundant GEM close for multi-plane DRI3 buffers #231

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19 changes: 19 additions & 0 deletions crates/muvm/src/guest/bridge/common.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -479,6 +479,9 @@ pub struct Client<'a, P: ProtocolHandler> {
debug_loop: DebugLoop,
pub send_queue: VecDeque<SendPacket>,
pub sub_poll: SubPoll<'a, P>,
/// Live GemHandleFinalizers per GEM handle. Multi-plane / same-BO DRI3 buffers
/// dedup several fds to one handle, so we refcount and close only on the last.
gem_handle_refs: HashMap<u32, u32>,
}

#[derive(Debug)]
Expand All @@ -493,6 +496,16 @@ pub struct GemHandleFinalizer(u32);

impl GemHandleFinalizer {
pub fn finalize<T: ProtocolHandler>(self, client: &mut Client<T>) -> Result<()> {
// Several fds can dedup to one handle (multi-plane / same-BO buffers), so a
// finalizer per fd would close it more than once -- EINVAL/ENOENT, tearing
// down the client. Close only on the last reference; real errors then matter.
if let Some(refs) = client.gem_handle_refs.get_mut(&self.0) {
if *refs > 1 {
*refs -= 1;
return Ok(());
}
client.gem_handle_refs.remove(&self.0);
}
// SAFETY: we own self.0
unsafe {
let close = DrmGemClose::new(self.0);
Expand Down Expand Up @@ -520,6 +533,7 @@ impl<'a, P: ProtocolHandler> Client<'a, P> {
debug_loop: DebugLoop::new(),
send_queue: VecDeque::new(),
sub_poll,
gem_handle_refs: HashMap::new(),
}));
{
let mut borrow = this.borrow_mut();
Expand Down Expand Up @@ -709,6 +723,11 @@ impl<'a, P: ProtocolHandler> Client<'a, P> {
unsafe {
drm_virtgpu_resource_info(self.gpu_ctx.fd.as_raw_fd() as c_int, &mut res_info)?;
}
// Count a live reference; only the last finalizer for this handle closes it.
self.gem_handle_refs
.entry(to_handle.handle)
.and_modify(|refcount| *refcount += 1)
.or_insert(1);
Ok((
CrossDomainResource {
identifier: res_info.res_handle,
Expand Down
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