[RFC PATCH 01/12] xen/manage: keep track of the on-going suspend mode

Anchal Agarwal
2018-06-12T20:56:08Z

From: Munehisa Kamata <kamatam@amazon.com>

To differentiate between Xen suspend, PM suspend and PM hibernation,
keep track of the on-going suspend mode by mainly using a new PM
notifier. Since Xen suspend doesn't have corresponding PM event, its
main logic is modfied to acquire pm_mutex and set the current mode.

Note that we may see deadlock if PM suspend/hibernation is interrupted
by Xen suspend. PM suspend/hibernation depends on xenwatch thread to
process xenbus state transactions, but the thread will sleep to wait
pm_mutex which is already held by PM suspend/hibernation context in the
scenario. Though, acquirng pm_mutex is still right thing to do, and we
would need to modify Xen shutdown code to avoid the issue. This will be
fixed by a separate patch.

Signed-off-by: Munehisa Kamata <kamatam@amazon.com>
Signed-off-by: Anchal Agarwal <anchalag@amazon.com>
Reviewed-by: Sebastian Biemueller <sbiemue@amazon.com>
Reviewed-by: Munehisa Kamata <kamatam@amazon.com>
Reviewed-by: Eduardo Valentin <eduval@amazon.com>
---
drivers/xen/manage.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 58 insertions(+)

diff --git a/drivers/xen/manage.c b/drivers/xen/manage.c
index 8835065..8f9ea87 100644
--- a/drivers/xen/manage.c
+++ b/drivers/xen/manage.c
@@ -13,6 +13,7 @@
#include <linux/freezer.h>
#include <linux/syscore_ops.h>
#include <linux/export.h>
+#include <linux/suspend.h>

#include <xen/xen.h>
#include <xen/xenbus.h>
@@ -39,6 +40,16 @@ enum shutdown_state {
/* Ignore multiple shutdown requests. */
static enum shutdown_state shutting_down = SHUTDOWN_INVALID;

+enum suspend_modes {
+ NO_SUSPEND = 0,
+ XEN_SUSPEND,
+ PM_SUSPEND,
+ PM_HIBERNATION,
+};
+
+/* Protected by pm_mutex */
+static enum suspend_modes suspend_mode = NO_SUSPEND;
+
struct suspend_info {
int cancelled;
};
@@ -98,6 +109,10 @@ static void do_suspend(void)
int err;
struct suspend_info si;

+ lock_system_sleep();
+
+ suspend_mode = XEN_SUSPEND;
+
shutting_down = SHUTDOWN_SUSPEND;

err = freeze_processes();
@@ -161,6 +176,10 @@ static void do_suspend(void)
thaw_processes();
out:
shutting_down = SHUTDOWN_INVALID;
+
+ suspend_mode = NO_SUSPEND;
+
+ unlock_system_sleep();
}
#endif /* CONFIG_HIBERNATE_CALLBACKS */

@@ -372,3 +391,42 @@ int xen_setup_shutdown_event(void)
EXPORT_SYMBOL_GPL(xen_setup_shutdown_event);

subsys_initcall(xen_setup_shutdown_event);
+
+static int xen_pm_notifier(struct notifier_block *notifier,
+ unsigned long pm_event, void *unused)
+{
+ switch (pm_event) {
+ case PM_SUSPEND_PREPARE:
+ suspend_mode = PM_SUSPEND;
+ break;
+ case PM_HIBERNATION_PREPARE:
+ case PM_RESTORE_PREPARE:
+ suspend_mode = PM_HIBERNATION;
+ break;
+ case PM_POST_SUSPEND:
+ case PM_POST_RESTORE:
+ case PM_POST_HIBERNATION:
+ /* Set back to the default */
+ suspend_mode = NO_SUSPEND;
+ break;
+ default:
+ pr_warn("Receive unknown PM event 0x%lx\n", pm_event);
+ return -EINVAL;
+ }
+
+ return 0;
+};
+
+static struct notifier_block xen_pm_notifier_block = {
+ .notifier_call = xen_pm_notifier
+};
+
+static int xen_setup_pm_notifier(void)
+{
+ if (!xen_hvm_domain())
+ return -ENODEV;
+
+ return register_pm_notifier(&xen_pm_notifier_block);
+}
+
+subsys_initcall(xen_setup_pm_notifier);
--
2.7.4