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-rw-r--r--util/qemu-thread-posix.c148
1 files changed, 0 insertions, 148 deletions
diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c
index b2e26e2..ba72544 100644
--- a/util/qemu-thread-posix.c
+++ b/util/qemu-thread-posix.c
@@ -317,154 +317,6 @@ void qemu_sem_wait(QemuSemaphore *sem)
qemu_mutex_unlock(&sem->mutex);
}
-#ifdef __linux__
-#include "qemu/futex.h"
-#else
-static inline void qemu_futex_wake(QemuEvent *ev, int n)
-{
- assert(ev->initialized);
- pthread_mutex_lock(&ev->lock);
- if (n == 1) {
- pthread_cond_signal(&ev->cond);
- } else {
- pthread_cond_broadcast(&ev->cond);
- }
- pthread_mutex_unlock(&ev->lock);
-}
-
-static inline void qemu_futex_wait(QemuEvent *ev, unsigned val)
-{
- assert(ev->initialized);
- pthread_mutex_lock(&ev->lock);
- if (ev->value == val) {
- pthread_cond_wait(&ev->cond, &ev->lock);
- }
- pthread_mutex_unlock(&ev->lock);
-}
-#endif
-
-/* Valid transitions:
- * - free->set, when setting the event
- * - busy->set, when setting the event, followed by qemu_futex_wake
- * - set->free, when resetting the event
- * - free->busy, when waiting
- *
- * set->busy does not happen (it can be observed from the outside but
- * it really is set->free->busy).
- *
- * busy->free provably cannot happen; to enforce it, the set->free transition
- * is done with an OR, which becomes a no-op if the event has concurrently
- * transitioned to free or busy.
- */
-
-#define EV_SET 0
-#define EV_FREE 1
-#define EV_BUSY -1
-
-void qemu_event_init(QemuEvent *ev, bool init)
-{
-#ifndef __linux__
- pthread_mutex_init(&ev->lock, NULL);
- pthread_cond_init(&ev->cond, NULL);
-#endif
-
- ev->value = (init ? EV_SET : EV_FREE);
- ev->initialized = true;
-}
-
-void qemu_event_destroy(QemuEvent *ev)
-{
- assert(ev->initialized);
- ev->initialized = false;
-#ifndef __linux__
- pthread_mutex_destroy(&ev->lock);
- pthread_cond_destroy(&ev->cond);
-#endif
-}
-
-void qemu_event_set(QemuEvent *ev)
-{
- assert(ev->initialized);
-
- /*
- * Pairs with both qemu_event_reset() and qemu_event_wait().
- *
- * qemu_event_set has release semantics, but because it *loads*
- * ev->value we need a full memory barrier here.
- */
- smp_mb();
- if (qatomic_read(&ev->value) != EV_SET) {
- int old = qatomic_xchg(&ev->value, EV_SET);
-
- /* Pairs with memory barrier in kernel futex_wait system call. */
- smp_mb__after_rmw();
- if (old == EV_BUSY) {
- /* There were waiters, wake them up. */
- qemu_futex_wake(ev, INT_MAX);
- }
- }
-}
-
-void qemu_event_reset(QemuEvent *ev)
-{
- assert(ev->initialized);
-
- /*
- * If there was a concurrent reset (or even reset+wait),
- * do nothing. Otherwise change EV_SET->EV_FREE.
- */
- qatomic_or(&ev->value, EV_FREE);
-
- /*
- * Order reset before checking the condition in the caller.
- * Pairs with the first memory barrier in qemu_event_set().
- */
- smp_mb__after_rmw();
-}
-
-void qemu_event_wait(QemuEvent *ev)
-{
- unsigned value;
-
- assert(ev->initialized);
-
- /*
- * qemu_event_wait must synchronize with qemu_event_set even if it does
- * not go down the slow path, so this load-acquire is needed that
- * synchronizes with the first memory barrier in qemu_event_set().
- *
- * If we do go down the slow path, there is no requirement at all: we
- * might miss a qemu_event_set() here but ultimately the memory barrier in
- * qemu_futex_wait() will ensure the check is done correctly.
- */
- value = qatomic_load_acquire(&ev->value);
- if (value != EV_SET) {
- if (value == EV_FREE) {
- /*
- * Leave the event reset and tell qemu_event_set that there are
- * waiters. No need to retry, because there cannot be a concurrent
- * busy->free transition. After the CAS, the event will be either
- * set or busy.
- *
- * This cmpxchg doesn't have particular ordering requirements if it
- * succeeds (moving the store earlier can only cause qemu_event_set()
- * to issue _more_ wakeups), the failing case needs acquire semantics
- * like the load above.
- */
- if (qatomic_cmpxchg(&ev->value, EV_FREE, EV_BUSY) == EV_SET) {
- return;
- }
- }
-
- /*
- * This is the final check for a concurrent set, so it does need
- * a smp_mb() pairing with the second barrier of qemu_event_set().
- * The barrier is inside the FUTEX_WAIT system call.
- */
- qemu_futex_wait(ev, EV_BUSY);
- }
-}
-
static __thread NotifierList thread_exit;
/*