[PULL 15/15] migration/rdma: source: poll cm_event from return path

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

From: Li Zhijian <lizhijian@cn.fujitsu.com>

source side always blocks if postcopy is only enabled at source side.
users are not able to cancel this migration in this case.

Let source side have chance to cancel this migration

Signed-off-by: Li Zhijian <lizhijian@cn.fujitsu.com>
Message-Id: <20210525080552.28259-4-lizhijian@cn.fujitsu.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
  Typo fix
---
 migration/rdma.c | 42 ++++++++++++++++++++++++++++++++++++++----
 1 file changed, 38 insertions(+), 4 deletions(-)

diff --git a/migration/rdma.c b/migration/rdma.c
index d829d08d07..1cdb4561f3 100644
--- a/migration/rdma.c
+++ b/migration/rdma.c
@@ -36,6 +36,7 @@
 #include <rdma/rdma_cma.h>
 #include "trace.h"
 #include "qom/object.h"
+#include <poll.h>
 
 /*
  * Print and error on both the Monitor and the Log file.
@@ -2460,7 +2461,36 @@ err_rdma_source_init:
     return -1;
 }
 
-static int qemu_rdma_connect(RDMAContext *rdma, Error **errp)
+static int qemu_get_cm_event_timeout(RDMAContext *rdma,
+                                     struct rdma_cm_event **cm_event,
+                                     long msec, Error **errp)
+{
+    int ret;
+    struct pollfd poll_fd = {
+                                .fd = rdma->channel->fd,
+                                .events = POLLIN,
+                                .revents = 0
+                            };
+
+    do {
+        ret = poll(&poll_fd, 1, msec);
+    } while (ret < 0 && errno == EINTR);
+
+    if (ret == 0) {
+        ERROR(errp, "poll cm event timeout");
+        return -1;
+    } else if (ret < 0) {
+        ERROR(errp, "failed to poll cm event, errno=%i", errno);
+        return -1;
+    } else if (poll_fd.revents & POLLIN) {
+        return rdma_get_cm_event(rdma->channel, cm_event);
+    } else {
+        ERROR(errp, "no POLLIN event, revent=%x", poll_fd.revents);
+        return -1;
+    }
+}
+
+static int qemu_rdma_connect(RDMAContext *rdma, Error **errp, bool return_path)
 {
     RDMACapabilities cap = {
                                 .version = RDMA_CONTROL_VERSION_CURRENT,
@@ -2498,7 +2528,11 @@ static int qemu_rdma_connect(RDMAContext *rdma, Error **errp)
         goto err_rdma_source_connect;
     }
 
-    ret = rdma_get_cm_event(rdma->channel, &cm_event);
+    if (return_path) {
+        ret = qemu_get_cm_event_timeout(rdma, &cm_event, 5000, errp);
+    } else {
+        ret = rdma_get_cm_event(rdma->channel, &cm_event);
+    }
     if (ret) {
         perror("rdma_get_cm_event after rdma_connect");
         ERROR(errp, "connecting to destination!");
@@ -4111,7 +4145,7 @@ void rdma_start_outgoing_migration(void *opaque,
     }
 
     trace_rdma_start_outgoing_migration_after_rdma_source_init();
-    ret = qemu_rdma_connect(rdma, errp);
+    ret = qemu_rdma_connect(rdma, errp, false);
 
     if (ret) {
         goto err;
@@ -4132,7 +4166,7 @@ void rdma_start_outgoing_migration(void *opaque,
             goto return_path_err;
         }
 
-        ret = qemu_rdma_connect(rdma_return_path, errp);
+        ret = qemu_rdma_connect(rdma_return_path, errp, true);
 
         if (ret) {
             goto return_path_err;
-- 
2.31.1