tree 3ec6be0d664633e7ed50eb684c715b64f0a1f230
parent 275a320702c057fd4d39f9f726e8df6465f3d447
author Shintaro Kawamura <kawasin@google.com> 1680245450 +0900
committer crosvm LUCI <crosvm-scoped@luci-project-accounts.iam.gserviceaccount.com> 1680501798 +0000

swap: fix deadlock on the vmm-swap enable operation

The deadlock could happen on this scenario:

1. User enables vmm-swap. The main process sends Command::Enable to the
   monitor process.
2. User request the current status at the same time. The main process
   sends Command::Status to the monitor process and wait for the
   response from the monitor process.
3. The monitor process start enabling vmm-swap. Sends
   VmSwapCommand::Suspend to the main process and wait for
   VmSwapResponse::SuspendCompleted.
4. The main process is blocked by the step 2 and the request from step 3
   is never consumed.

The root issue issue is that Command::Status can be inserted between
Command::Enable and VmSwapCommand::Suspend. This CL simplifies the
communication between the main and monitor processes on enabling
vmm-swap and resolve the deadlock.

VmSwapCommand and corresponding Tube was added by
https://crrev.com/c/4293656, but is now removed by this CL.

BUG=b:275671628
TEST=manual test

Change-Id: Ia838b1feddb4a3f41bd729e9147adc5e2df866aa
Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/4387662
Reviewed-by: David Stevens <stevensd@chromium.org>
Commit-Queue: Shin Kawamura <kawasin@google.com>