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

[Anchal Agarwal <anchalag@xxxxxxxxxx>]

From: Munehisa Kamata <kamatam@xxxxxxxxxx>

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@xxxxxxxxxx>
Signed-off-by: Anchal Agarwal <anchalag@xxxxxxxxxx>
Reviewed-by: Sebastian Biemueller <sbiemue@xxxxxxxxxx>
Reviewed-by: Munehisa Kamata <kamatam@xxxxxxxxxx>
Reviewed-by: Eduardo Valentin <eduval@xxxxxxxxxx>
---
 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


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel