[Bug 56981] New: Mouse movement causes huge CPU spikes when using WINEESYNC.

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=56981

Bug ID: 56981
           Summary: Mouse movement causes huge CPU spikes when using
                    WINEESYNC.
           Product: Wine-staging
           Version: 9.13
          Hardware: x86-64
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: -unknown
          Assignee: [e-mail]
          Reporter: [e-mail]
                CC: [e-mail], [e-mail]
   Regression SHA1: e479cad86f1f7de5d2a0a0d1398e7733c0aaef3e
      Distribution: ArchLinux

The problem occurs every time when Wine is launched with WINEESYNC=1 - doesn't
matter the application or the type of desktop used (virtual/non-virtual). It
also happens when wine apps are in background, i.e. the topmost window is from
a Linux app, etc. (As a side note Proton's fsync patchset is also affected.)

The process with highest CPU usage is c:\windows\system32\explorer.exe (~70%)
followed by /usr/bin/wineserver (~40%) - on a 6 core Intel CPU (12 virtual
cores).
Normally these processes have very low CPU usage (<1%) on mouse movement.

I did manual bisect on the wine-development tree and found that commit
90dcd2eaa6b6a2afaf298f1e457938350b0becfc "win32u: Use the thread message queue
shared memory in peek_message." was causing the problem with the
eventfd_synchronization patchset.
After reverting this commit + the other two related win32u commits, CPU usage
is back to normal when using esync.

Steps to reproduce:
1. Launch any Wine app - for example "winecfg".
2. Move the mouse pointer intensively.
3. See the CPU usage.