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[Qemu-devel] [PATCH v3 2/7] net: distinguish & defer nested call to BH
From: |
Liu Ping Fan |
Subject: |
[Qemu-devel] [PATCH v3 2/7] net: distinguish & defer nested call to BH |
Date: |
Thu, 27 Jun 2013 11:38:44 +0800 |
When network layer can run on multi-thread, nested call caused by
nc->receive() will raise issue like deadlock. So postpone it to BH.
We distinguish nested call "A->B->A" from parallel call "A->B, B->A"
by using tls variable net_enter. Here A, B stands for a NetClientState.
Signed-off-by: Liu Ping Fan <address@hidden>
---
net/queue.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 46 insertions(+), 2 deletions(-)
diff --git a/net/queue.c b/net/queue.c
index 1937345..d508b7a 100644
--- a/net/queue.c
+++ b/net/queue.c
@@ -24,6 +24,9 @@
#include "net/queue.h"
#include "qemu/queue.h"
#include "net/net.h"
+#include "block/aio.h"
+#include "qemu/main-loop.h"
+#include "qemu/tls.h"
/* The delivery handler may only return zero if it will call
* qemu_net_queue_flush() when it determines that it is once again able
@@ -58,6 +61,23 @@ struct NetQueue {
unsigned delivering : 1;
};
+typedef struct NetQueueBH {
+ QEMUBH *bh;
+ NetClientState *nc;
+} NetQueueBH;
+
+static void qemu_net_queue_send_bh(void *opaque)
+{
+ NetQueueBH *q_bh = opaque;
+ NetQueue *queue = q_bh->nc->send_queue;
+
+ qemu_net_queue_flush(queue);
+ qemu_bh_delete(q_bh->bh);
+ g_slice_free(NetQueueBH, q_bh);
+}
+
+DEFINE_TLS(int, net_enter) = 0;
+
NetQueue *qemu_new_net_queue(NetClientState *nc)
{
NetQueue *queue;
@@ -183,9 +203,20 @@ ssize_t qemu_net_queue_send(NetQueue *queue,
NetPacketSent *sent_cb)
{
ssize_t ret;
+ int reenter;
- if (queue->delivering || !qemu_can_send_packet(sender)) {
+ reenter = ++tls_var(net_enter);
+ assert(reenter <= 2);
+ if (queue->delivering || !qemu_can_send_packet(sender) ||
+ reenter == 2) {
qemu_net_queue_append(queue, sender, flags, data, size, sent_cb);
+ if (reenter == 2) {
+ NetQueueBH *que_bh = g_slice_new(NetQueueBH);
+ que_bh->bh = qemu_bh_new(qemu_net_queue_send_bh, que_bh);
+ que_bh->nc = queue->nc;
+ qemu_bh_schedule(que_bh->bh);
+ --tls_var(net_enter);
+ }
return 0;
}
@@ -196,6 +227,7 @@ ssize_t qemu_net_queue_send(NetQueue *queue,
}
qemu_net_queue_flush(queue);
+ --tls_var(net_enter);
return ret;
}
@@ -208,9 +240,20 @@ ssize_t qemu_net_queue_send_iov(NetQueue *queue,
NetPacketSent *sent_cb)
{
ssize_t ret;
+ int reenter;
- if (queue->delivering || !qemu_can_send_packet(sender)) {
+ reenter = ++tls_var(net_enter);
+ assert(reenter <= 2);
+ if (queue->delivering || !qemu_can_send_packet(sender) ||
+ reenter == 2) {
qemu_net_queue_append_iov(queue, sender, flags, iov, iovcnt, sent_cb);
+ if (reenter == 2) {
+ NetQueueBH *que_bh = g_slice_new(NetQueueBH);
+ que_bh->bh = qemu_bh_new(qemu_net_queue_send_bh, que_bh);
+ que_bh->nc = queue->nc;
+ qemu_bh_schedule(que_bh->bh);
+ --tls_var(net_enter);
+ }
return 0;
}
@@ -221,6 +264,7 @@ ssize_t qemu_net_queue_send_iov(NetQueue *queue,
}
qemu_net_queue_flush(queue);
+ --tls_var(net_enter);
return ret;
}
--
1.8.1.4
- [Qemu-devel] [PATCH v3 0/7] port network layer onto glib, Liu Ping Fan, 2013/06/26
- [Qemu-devel] [PATCH v3 1/7] net: force NetQue opaque to be NetClientState, Liu Ping Fan, 2013/06/26
- [Qemu-devel] [PATCH v3 2/7] net: distinguish & defer nested call to BH,
Liu Ping Fan <=
- [Qemu-devel] [PATCH v3 3/7] net: introduce lock to protect NetQueue, Liu Ping Fan, 2013/06/26
- [Qemu-devel] [PATCH v3 4/7] net: introduce lock to protect NetClientState's peer's access, Liu Ping Fan, 2013/06/26
- [Qemu-devel] [PATCH v3 5/7] net: introduce lock to protect net clients, Liu Ping Fan, 2013/06/26
- [Qemu-devel] [PATCH v3 6/7] net: using refcnt to manage NetClientState, Liu Ping Fan, 2013/06/26
- [Qemu-devel] [PATCH v3 7/7] net: hub use lock to protect ports list, Liu Ping Fan, 2013/06/26