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From:   Anchal Agarwal <anchalag@amazon.com>
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Subject: [RFC PATCH 01/12] xen/manage: keep track of the on-going suspend mode
Date:   Tue, 12 Jun 2018 20:56:08 +0000
Message-ID: <20180612205619.28156-2-anchalag@amazon.com>
In-Reply-To: <20180612205619.28156-1-anchalag@amazon.com>
References: <20180612205619.28156-1-anchalag@amazon.com>
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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