GitLab

SpinningFutex is essentially an OS-provided lock with spinning in
userspace before sleeping. This is implemented on Linux using futex(),
which is not available on Windows. However, SRWLocks have the
TryAcquireSRWLockExclusive() function which is functionally equivalent
to the userspace CAS for futex()s.

This CL:
- Renames SpinningFutex to SpinningMutex
- Extracts the common code
- Extends it to Windows by using SRWLock instead of futex()

The fast path is likely a bit slower than on Linux, as there is still an
external function call, but it should be pretty comparable.

Bug: 1061437
Change-Id: I7d71055865568738a569d7252f38a7a6773795e0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2467916
Commit-Queue: Benoit L <lizeb@chromium.org>
Reviewed-by: Bartek Nowierski <bartekn@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#816987}