RAMBlock *block;
/* The list is protected by the iothread lock here. */
- block = ram_list.mru_block;
+ block = atomic_rcu_read(&ram_list.mru_block);
if (block && addr - block->offset < block->max_length) {
goto found;
}
abort();
found:
+ /* It is safe to write mru_block outside the iothread lock. This
+ * is what happens:
+ *
+ * mru_block = xxx
+ * rcu_read_unlock()
+ * xxx removed from list
+ * rcu_read_lock()
+ * read mru_block
+ * mru_block = NULL;
+ * call_rcu(reclaim_ramblock, xxx);
+ * rcu_read_unlock()
+ *
+ * atomic_rcu_set is not needed here. The block was already published
+ * when it was placed into the list. Here we're just making an extra
+ * copy of the pointer.
+ */
ram_list.mru_block = block;
return block;
}
QTAILQ_REMOVE(&ram_list.blocks, block, next);
ram_list.mru_block = NULL;
ram_list.version++;
- g_free(block);
+ g_free_rcu(block, rcu);
break;
}
}
qemu_mutex_unlock_ramlist();
}
+static void reclaim_ramblock(RAMBlock *block)
+{
+ if (block->flags & RAM_PREALLOC) {
+ ;
+ } else if (xen_enabled()) {
+ xen_invalidate_map_cache_entry(block->host);
+#ifndef _WIN32
+ } else if (block->fd >= 0) {
+ munmap(block->host, block->max_length);
+ close(block->fd);
+#endif
+ } else {
+ qemu_anon_ram_free(block->host, block->max_length);
+ }
+ g_free(block);
+}
+
+/* Called with the iothread lock held */
void qemu_ram_free(ram_addr_t addr)
{
RAMBlock *block;
QTAILQ_REMOVE(&ram_list.blocks, block, next);
ram_list.mru_block = NULL;
ram_list.version++;
- if (block->flags & RAM_PREALLOC) {
- ;
- } else if (xen_enabled()) {
- xen_invalidate_map_cache_entry(block->host);
-#ifndef _WIN32
- } else if (block->fd >= 0) {
- munmap(block->host, block->max_length);
- close(block->fd);
-#endif
- } else {
- qemu_anon_ram_free(block->host, block->max_length);
- }
- g_free(block);
+ call_rcu(block, reclaim_ramblock, rcu);
break;
}
}