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[PATCH v2 2/7] Implement drain_call_rcu and use it in hmp_device_del
From: |
Maxim Levitsky |
Subject: |
[PATCH v2 2/7] Implement drain_call_rcu and use it in hmp_device_del |
Date: |
Mon, 11 May 2020 19:09:46 +0300 |
This allows to preserve the semantics of hmp_device_del,
that the device is deleted immediatly which was changed by previos
patch that delayed this to RCU callback
Suggested-by: Stefan Hajnoczi <address@hidden>
Signed-off-by: Maxim Levitsky <address@hidden>
---
include/qemu/rcu.h | 1 +
qdev-monitor.c | 3 +++
util/rcu.c | 33 +++++++++++++++++++++++++++++++++
3 files changed, 37 insertions(+)
diff --git a/include/qemu/rcu.h b/include/qemu/rcu.h
index 570aa603eb..0e375ebe13 100644
--- a/include/qemu/rcu.h
+++ b/include/qemu/rcu.h
@@ -133,6 +133,7 @@ struct rcu_head {
};
extern void call_rcu1(struct rcu_head *head, RCUCBFunc *func);
+extern void drain_call_rcu(void);
/* The operands of the minus operator must have the same type,
* which must be the one that we specify in the cast.
diff --git a/qdev-monitor.c b/qdev-monitor.c
index 56cee1483f..70877840a2 100644
--- a/qdev-monitor.c
+++ b/qdev-monitor.c
@@ -812,6 +812,8 @@ void qmp_device_add(QDict *qdict, QObject **ret_data, Error
**errp)
return;
}
dev = qdev_device_add(opts, &local_err);
+ drain_call_rcu();
+
if (!dev) {
error_propagate(errp, local_err);
qemu_opts_del(opts);
@@ -904,6 +906,7 @@ void qmp_device_del(const char *id, Error **errp)
}
qdev_unplug(dev, errp);
+ drain_call_rcu();
}
}
diff --git a/util/rcu.c b/util/rcu.c
index 60a37f72c3..e8b1c4d6c5 100644
--- a/util/rcu.c
+++ b/util/rcu.c
@@ -293,6 +293,39 @@ void call_rcu1(struct rcu_head *node, void (*func)(struct
rcu_head *node))
qemu_event_set(&rcu_call_ready_event);
}
+
+struct rcu_drain {
+ struct rcu_head rcu;
+ QemuEvent drain_complete_event;
+};
+
+static void drain_rcu_callback(struct rcu_head *node)
+{
+ struct rcu_drain *event = (struct rcu_drain *)node;
+ qemu_event_set(&event->drain_complete_event);
+}
+
+void drain_call_rcu(void)
+{
+ struct rcu_drain rcu_drain;
+ bool locked = qemu_mutex_iothread_locked();
+
+ memset(&rcu_drain, 0, sizeof(struct rcu_drain));
+
+ if (locked) {
+ qemu_mutex_unlock_iothread();
+ }
+
+ qemu_event_init(&rcu_drain.drain_complete_event, false);
+ call_rcu1(&rcu_drain.rcu, drain_rcu_callback);
+ qemu_event_wait(&rcu_drain.drain_complete_event);
+
+ if (locked) {
+ qemu_mutex_lock_iothread();
+ }
+
+}
+
void rcu_register_thread(void)
{
assert(rcu_reader.ctr == 0);
--
2.17.2
- [PATCH v2 0/7] RFC/WIP: Fix scsi devices plug/unplug races w.r.t virtio-scsi iothread, Maxim Levitsky, 2020/05/11
- [PATCH v2 1/7] scsi/scsi_bus: switch search direction in scsi_device_find, Maxim Levitsky, 2020/05/11
- [PATCH v2 2/7] Implement drain_call_rcu and use it in hmp_device_del,
Maxim Levitsky <=
- [PATCH v2 3/7] device-core: use RCU for list of childs of a bus, Maxim Levitsky, 2020/05/11
- [PATCH v2 4/7] device-core: use atomic_set on .realized property, Maxim Levitsky, 2020/05/11
- [PATCH v2 5/7] virtio-scsi: don't touch scsi devices that are not yet realized or about to be un-realized, Maxim Levitsky, 2020/05/11
- [PATCH v2 6/7] scsi: Add scsi_device_get, Maxim Levitsky, 2020/05/11
- [PATCH v2 7/7] virtio-scsi: use scsi_device_get, Maxim Levitsky, 2020/05/11