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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH v2] systemd: Add hooks to stop/start xen-watchdog on suspend/resume
From: Mykola Kvach <mykola_kvach@xxxxxxxx>
This patch adds a systemd sleep hook script to stop the xen-watchdog
service before system suspend and start it again after resume.
Stopping the watchdog before a system suspend operation may look unsafe.
Let's imagine the following situation: 'systemctl suspend' does not
interact with the running service at all. In such a case, the Xen
watchdog daemon freezes just before suspend. If this happens, for
example, right before sending a ping, and Xen has not yet marked the
domain as suspended (is_shutting_down), the Xen watchdog timer may
trigger a false alert.
This is an almost impossible situation, because typically:
ping time = watchdog timeout / 2
and the watchdog timeout is usually set to a relatively large value
(dozens of seconds).
Still, this is more likely with very short watchdog timeouts. It may
happen in the following scenarios:
* Significant delays occur between freezing Linux tasks and
triggering the ACPI or PSCI sleep request or handler.
* Long delays happen inside Xen between the entrance to the sleep
trigger and the actual forwarding of the sleep request further.
A similar situation may occur on resume with short timeouts. During the
resume operation, Xen restores timers and the domain context. The Xen
watchdog timer also resumes. If it schedules the domain right before the
watchdog timeout expires, and the daemon responsible for pinging is not
yet running, a timeout might occur.
Both scenarios are rare and typically require very small watchdog
timeouts combined with significant delays in Xen or the Linux kernel
during suspend/resume flows.
Conceptually, however, if activating and pinging the Xen watchdog is the
responsibility of the domain and its services, then the domain should
also manage the watchdog service/daemon lifecycle. This is similar to
what is already done by the Xen watchdog driver inside the Linux kernel.
Signed-off-by: Mykola Kvach <mykola_kvach@xxxxxxxx>
---
Changes in V2:
- drop logging to separate files
- remove checks for xen-watchdog service existence at start of sleep script
- use XEN_RUN_DIR for saving watchdog service state before sleep
- remove loop when installing sleep script for xen-watchdog service
- introduce new configs XEN_SYSTEMD_SLEEP_DIR, SYSTEMD_SLEEP_DIR, and
with-systemd-sleep
---
config/Tools.mk.in | 1 +
m4/systemd.m4 | 14 ++++++++
tools/hotplug/Linux/systemd/Makefile | 8 ++++-
.../Linux/systemd/xen-watchdog-sleep.sh | 34 +++++++++++++++++++
4 files changed, 56 insertions(+), 1 deletion(-)
create mode 100644 tools/hotplug/Linux/systemd/xen-watchdog-sleep.sh
diff --git a/config/Tools.mk.in b/config/Tools.mk.in
index 463ab75965..e47ac23d11 100644
--- a/config/Tools.mk.in
+++ b/config/Tools.mk.in
@@ -53,6 +53,7 @@ CONFIG_LIBFSIMAGE := @libfsimage@
CONFIG_SYSTEMD := @systemd@
XEN_SYSTEMD_DIR := @SYSTEMD_DIR@
XEN_SYSTEMD_MODULES_LOAD := @SYSTEMD_MODULES_LOAD@
+XEN_SYSTEMD_SLEEP_DIR := @SYSTEMD_SLEEP_DIR@
CONFIG_9PFS := @ninepfs@
LINUX_BACKEND_MODULES := @LINUX_BACKEND_MODULES@
diff --git a/m4/systemd.m4 b/m4/systemd.m4
index ab12ea313d..ee684d3391 100644
--- a/m4/systemd.m4
+++ b/m4/systemd.m4
@@ -28,6 +28,12 @@ AC_DEFUN([AX_SYSTEMD_OPTIONS], [
[set directory for systemd modules load files
[PREFIX/lib/modules-load.d/]]),
[SYSTEMD_MODULES_LOAD="$withval"], [SYSTEMD_MODULES_LOAD=""])
AC_SUBST(SYSTEMD_MODULES_LOAD)
+
+ AC_ARG_WITH(systemd-sleep,
+ AS_HELP_STRING([--with-systemd-sleep=DIR],
+ [set directory for systemd sleep script files
[PREFIX/lib/systemd/system-sleep/]]),
+ [SYSTEMD_SLEEP_DIR="$withval"], [SYSTEMD_SLEEP_DIR=""])
+ AC_SUBST(SYSTEMD_SLEEP_DIR)
])
AC_DEFUN([AX_ENABLE_SYSTEMD_OPTS], [
@@ -69,6 +75,14 @@ AC_DEFUN([AX_CHECK_SYSTEMD_LIBS], [
AS_IF([test "x$SYSTEMD_MODULES_LOAD" = x], [
AC_MSG_ERROR([SYSTEMD_MODULES_LOAD is unset])
], [])
+
+ AS_IF([test "x$SYSTEMD_SLEEP_DIR" = x], [
+ SYSTEMD_SLEEP_DIR="\$(prefix)/lib/systemd/system-sleep/"
+ ], [])
+
+ AS_IF([test "x$SYSTEMD_SLEEP_DIR" = x], [
+ AC_MSG_ERROR([SYSTEMD_SLEEP_DIR is unset])
+ ], [])
])
AC_DEFUN([AX_CHECK_SYSTEMD], [
diff --git a/tools/hotplug/Linux/systemd/Makefile
b/tools/hotplug/Linux/systemd/Makefile
index e29889156d..579ef9d87d 100644
--- a/tools/hotplug/Linux/systemd/Makefile
+++ b/tools/hotplug/Linux/systemd/Makefile
@@ -5,6 +5,8 @@ XEN_SYSTEMD_MODULES := xen.conf
XEN_SYSTEMD_MOUNT := proc-xen.mount
+XEN_SYSTEMD_SLEEP_SCRIPT := xen-watchdog-sleep.sh
+
XEN_SYSTEMD_SERVICE := xenstored.service
XEN_SYSTEMD_SERVICE += xenconsoled.service
XEN_SYSTEMD_SERVICE += xen-qemu-dom0-disk-backend.service
@@ -15,7 +17,8 @@ XEN_SYSTEMD_SERVICE += xendriverdomain.service
ALL_XEN_SYSTEMD := $(XEN_SYSTEMD_MODULES) \
$(XEN_SYSTEMD_MOUNT) \
- $(XEN_SYSTEMD_SERVICE)
+ $(XEN_SYSTEMD_SERVICE) \
+ $(XEN_SYSTEMD_SLEEP_SCRIPT)
.PHONY: all
all: $(ALL_XEN_SYSTEMD)
@@ -31,15 +34,18 @@ distclean: clean
install: $(ALL_XEN_SYSTEMD)
$(INSTALL_DIR) $(DESTDIR)$(XEN_SYSTEMD_DIR)
$(INSTALL_DIR) $(DESTDIR)$(XEN_SYSTEMD_MODULES_LOAD)
+ $(INSTALL_DIR) $(DESTDIR)$(XEN_SYSTEMD_SLEEP_DIR)
$(INSTALL_DATA) *.service $(DESTDIR)$(XEN_SYSTEMD_DIR)
$(INSTALL_DATA) *.mount $(DESTDIR)$(XEN_SYSTEMD_DIR)
$(INSTALL_DATA) *.conf $(DESTDIR)$(XEN_SYSTEMD_MODULES_LOAD)
+ $(INSTALL_PROG) $(XEN_SYSTEMD_SLEEP_SCRIPT)
$(DESTDIR)$(XEN_SYSTEMD_SLEEP_DIR)
.PHONY: uninstall
uninstall:
rm -f $(DESTDIR)$(XEN_SYSTEMD_MODULES_LOAD)/*.conf
rm -f $(DESTDIR)$(XEN_SYSTEMD_DIR)/*.mount
rm -f $(DESTDIR)$(XEN_SYSTEMD_DIR)/*.service
+ rm -f $(DESTDIR)$(XEN_SYSTEMD_SLEEP_DIR)/$(XEN_SYSTEMD_SLEEP_SCRIPT)
$(XEN_SYSTEMD_MODULES):
rm -f $@.tmp
diff --git a/tools/hotplug/Linux/systemd/xen-watchdog-sleep.sh
b/tools/hotplug/Linux/systemd/xen-watchdog-sleep.sh
new file mode 100644
index 0000000000..e9bdadc8fa
--- /dev/null
+++ b/tools/hotplug/Linux/systemd/xen-watchdog-sleep.sh
@@ -0,0 +1,34 @@
+#!/bin/sh
+
+# The first argument ($1) is:
+# "pre" or "post"
+# The second argument ($2) is:
+# "suspend", "hibernate", "hybrid-sleep", or "suspend-then-hibernate"
+
+. /etc/xen/scripts/hotplugpath.sh
+
+SERVICE_NAME="xen-watchdog.service"
+STATE_FILE="${XEN_RUN_DIR}/xen-watchdog-sleep-flag"
+
+case "$1" in
+pre)
+ if systemctl is-active --quiet "${SERVICE_NAME}"; then
+ touch "${STATE_FILE}"
+ echo "Stopping ${SERVICE_NAME} before $2."
+ systemctl stop "${SERVICE_NAME}"
+ fi
+ ;;
+post)
+ if [ -f "${STATE_FILE}" ]; then
+ echo "Starting ${SERVICE_NAME} after $2."
+ systemctl start "${SERVICE_NAME}"
+ rm "${STATE_FILE}"
+ fi
+ ;;
+*)
+ echo "Script called with unknown action '$1'. Arguments: '$@'"
+ exit 1
+ ;;
+esac
+
+exit 0
--
2.48.1
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