[v10,12/25] tools/xenstore: allow live update only with no transaction active

Commit Message

Jürgen Groß Dec. 15, 2020, 4:35 p.m. UTC

In order to simplify live update state dumping only allow live update
to happen when no transaction is active.

A timeout is used to detect guests which have a transaction active for
longer periods of time. In case such a guest is detected when trying
to do a live update it will be reported and the update will fail.

The admin can then either use a longer timeout, or use the force flag
to just ignore the transactions of such a guest, or kill the guest
before retrying.

Transactions that have been active for a shorter time than the timeout
will end in the live update starting to respond "BUSY" without
aborting the complete live update process. The xenstore-control
program will then just repeat the live update starting until a
different result is returned.

Signed-off-by: Juergen Gross <[e-mail]>
Reviewed-by: Paul Durrant <[e-mail]>
Acked-by: Julien Grall <[e-mail]>
---
 tools/xenstore/xenstored_control.c     | 20 +++++++++++++++++++-
 tools/xenstore/xenstored_core.h        |  1 +
 tools/xenstore/xenstored_transaction.c |  5 +++++
 3 files changed, 25 insertions(+), 1 deletion(-)

Patch

diff --git a/tools/xenstore/xenstored_control.c b/tools/xenstore/xenstored_control.c
index 940b717741..af64a9a2d4 100644
--- a/tools/xenstore/xenstored_control.c
+++ b/tools/xenstore/xenstored_control.c
@@ -22,6 +22,7 @@  Interactive commands for Xen Store Daemon.
 #include <stdlib.h>
 #include <string.h>
 #include <syslog.h>
+#include <time.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <unistd.h>
@@ -307,7 +308,24 @@  static const char *lu_arch(const void *ctx, struct connection *conn,
 static const char *lu_check_lu_allowed(const void *ctx, bool force,
 				       unsigned int to)
 {
-	return NULL;
+	char *ret = NULL;
+	struct connection *conn;
+	time_t now = time(NULL);
+	bool busy = false;
+
+	list_for_each_entry(conn, &connections, list) {
+		if (conn->ta_start_time - now >= to && !force) {
+			ret = talloc_asprintf(ctx, "%s\nDomain %u: %ld s",
+					      ret ? : "Domains with long running transactions:",
+					      conn->id,
+					      conn->ta_start_time - now);
+			if (!ret)
+				busy = true;
+		} else if (conn->ta_start_time)
+			busy = true;
+	}
+
+	return ret ? (const char *)ret : (busy ? "BUSY" : NULL);
 }
 
 static const char *lu_dump_state(const void *ctx, struct connection *conn)
diff --git a/tools/xenstore/xenstored_core.h b/tools/xenstore/xenstored_core.h
index 27826c125c..a009b182fd 100644
--- a/tools/xenstore/xenstored_core.h
+++ b/tools/xenstore/xenstored_core.h
@@ -93,6 +93,7 @@  struct connection
 	struct list_head transaction_list;
 	uint32_t next_transaction_id;
 	unsigned int transaction_started;
+	time_t ta_start_time;
 
 	/* The domain I'm associated with, if any. */
 	struct domain *domain;
diff --git a/tools/xenstore/xenstored_transaction.c b/tools/xenstore/xenstored_transaction.c
index 52355f4ed8..cd07fb0f21 100644
--- a/tools/xenstore/xenstored_transaction.c
+++ b/tools/xenstore/xenstored_transaction.c
@@ -473,6 +473,8 @@  int do_transaction_start(struct connection *conn, struct buffered_data *in)
 	list_add_tail(&trans->list, &conn->transaction_list);
 	talloc_steal(conn, trans);
 	talloc_set_destructor(trans, destroy_transaction);
+	if (!conn->transaction_started)
+		conn->ta_start_time = time(NULL);
 	conn->transaction_started++;
 	wrl_ntransactions++;
 
@@ -511,6 +513,8 @@  int do_transaction_end(struct connection *conn, struct buffered_data *in)
 	conn->transaction = NULL;
 	list_del(&trans->list);
 	conn->transaction_started--;
+	if (!conn->transaction_started)
+		conn->ta_start_time = 0;
 
 	/* Attach transaction to in for auto-cleanup */
 	talloc_steal(in, trans);
@@ -589,6 +593,7 @@  void conn_delete_all_transactions(struct connection *conn)
 	assert(conn->transaction == NULL);
 
 	conn->transaction_started = 0;
+	conn->ta_start_time = 0;
 }
 
 int check_transactions(struct hashtable *hash)