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7c9b2bf677
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>
35 lines
555 B
C
35 lines
555 B
C
#ifndef __QEMU_THREAD_WIN32_H
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#define __QEMU_THREAD_WIN32_H 1
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#include "windows.h"
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struct QemuMutex {
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CRITICAL_SECTION lock;
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LONG owner;
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};
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struct QemuCond {
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LONG waiters, target;
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HANDLE sema;
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HANDLE continue_event;
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};
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struct QemuSemaphore {
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HANDLE sema;
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};
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struct QemuEvent {
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int value;
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HANDLE event;
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};
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typedef struct QemuThreadData QemuThreadData;
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struct QemuThread {
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QemuThreadData *data;
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unsigned tid;
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};
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/* Only valid for joinable threads. */
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HANDLE qemu_thread_get_handle(QemuThread *thread);
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#endif
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