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QemuEvents are used heavily by call_rcu. We do not want them to be slow, but the current implementation does a kernel call on every invocation of qemu_event_* and won't cut it. So, wrap a Win32 manual-reset event with a fast userspace path. The states and transitions are the same as for the futex and mutex/condvar implementations, but the slow path is different of course. The idea is to reset the Win32 event lazily, as part of a test-reset-test-wait sequence. Such a sequence is, indeed, how QemuEvents are used by RCU and other subsystems! The patch includes a formal model of the algorithm. Tested-by: Stefan Weil <sw@weilnetz.de> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Stefan Weil <sw@weilnetz.de>
Read the documentation in qemu-doc.html or on http://wiki.qemu-project.org - QEMU team