if (mis->preempt_thread_status == PREEMPT_THREAD_CREATED) {
/* Notify the fast load thread to quit */
mis->preempt_thread_status = PREEMPT_THREAD_QUIT;
+ /*
+ * Update preempt_thread_status before reading count. Note: mutex
+ * lock only provide ACQUIRE semantic, and it doesn't stops this
+ * write to be reordered after reading the count.
+ */
+ smp_mb();
+ /*
+ * It's possible that the preempt thread is still handling the last
+ * pages to arrive which were requested by guest page faults.
+ * Making sure nothing is left behind by waiting on the condvar if
+ * that unlikely case happened.
+ */
+ WITH_QEMU_LOCK_GUARD(&mis->page_request_mutex) {
+ if (qatomic_read(&mis->page_requested_count)) {
+ /*
+ * It is guaranteed to receive a signal later, because the
+ * count>0 now, so it's destined to be decreased to zero
+ * very soon by the preempt thread.
+ */
+ qemu_cond_wait(&mis->page_request_cond,
+ &mis->page_request_mutex);
+ }
+ }
+ /* Notify the fast load thread to quit */
if (mis->postcopy_qemufile_dst) {
qemu_file_shutdown(mis->postcopy_qemufile_dst);
}
*/
if (g_tree_lookup(mis->page_requested, host_addr)) {
g_tree_remove(mis->page_requested, host_addr);
- mis->page_requested_count--;
+ int left_pages = qatomic_dec_fetch(&mis->page_requested_count);
+
trace_postcopy_page_req_del(host_addr, mis->page_requested_count);
+ /* Order the update of count and read of preempt status */
+ smp_mb();
+ if (mis->preempt_thread_status == PREEMPT_THREAD_QUIT &&
+ left_pages == 0) {
+ /*
+ * This probably means the main thread is waiting for us.
+ * Notify that we've finished receiving the last requested
+ * page.
+ */
+ qemu_cond_signal(&mis->page_request_cond);
+ }
}
qemu_mutex_unlock(&mis->page_request_mutex);
mark_postcopy_blocktime_end((uintptr_t)host_addr);