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wl: avoid inserting empty virtio queue entries

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The kernel driver currently short circuits the check for empty queue
entries if the entry arrives empty. Ordinarily the check is run every
time data is taken out of a queue entry and would recycle the entry once
empty. The short circuiting is being fixed in the kernel, but this
device change fixes the unnecessary empty queue entries from happening
in the first place.

BUG=chromium:791724
TEST=test code from the BUG

Change-Id: I5b72aac843def052bfe1234dfbde236274ae02bb
Reviewed-on: https://chromium-review.googlesource.com/974883
Commit-Ready: Zach Reizner <zachr@chromium.org>
Tested-by: Zach Reizner <zachr@chromium.org>
Reviewed-by: Stephen Barber <smbarber@chromium.org>
This commit is contained in:
Zach Reizner 2018-03-21 21:40:53 -07:00 committed by chrome-bot
parent 63be8cb9d3
commit 5fc80ebd71
1 changed files with 5 additions and 0 deletions
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5
devices/src/virtio/wl.rs
View file

@ -642,6 +642,11 @@ impl WlState {
Some(vfd) => vfd.recv(&mut self.scm, &mut self.in_file_queue)?,
None => return Ok(()),
};
// Short-circuit the empty recv case to avoid putting empty recv commands into the virtio
// queue.
if self.in_file_queue.is_empty() && buf.is_empty() {
return Ok(())
}
for file in self.in_file_queue.drain(..) {
self.vfds
.insert(self.next_vfd_id, WlVfd::from_file(self.vm.clone(), file)?);