Suspend: Testing facility (rev. 2)

Introduce sysfs attribute /sys/power/pm_test allowing one to test the suspend
core code.  Namely, writing one of the strings:

freezer
devices
platform
processors
core

to this file causes the suspend code to work in one of the test modes defined as
follows:

freezer
- test the freezing of processes

devices
- test the freezing of processes and suspending of devices

platform
- test the freezing of processes, suspending of devices and platform global
  control methods(*)

processors
- test the freezing of processes, suspending of devices, platform global
  control methods and the disabling of nonboot CPUs

core
- test the freezing of processes, suspending of devices, platform global
  control methods, the disabling of nonboot CPUs and suspending of
  platform/system devices

(*) These are ACPI global control methods on ACPI systems

Then, if a suspend is started by normal means, the suspend core will perform
its normal operations up to the point indicated by given test level.  Next, it
will wait for 5 seconds and carry out the resume operations needed to transition
the system back to the fully functional state.

Writing "none" to /sys/power/pm_test turns the testing off.

When open for reading, /sys/power/pm_test contains a space-separated list of all
available tests (including "none" that represents the normal functionality) in
which the current test level is indicated by square brackets.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Len Brown <len.brown@intel.com>

2 files changed, 117 insertions, 9 deletions

diff --git a/kernel/power/main.c b/kernel/power/main.c
index efc08360e627..84e1ae63bb8c 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -31,6 +31,79 @@ DEFINE_MUTEX(pm_mutex);
 unsigned int pm_flags;
 EXPORT_SYMBOL(pm_flags);
 
+#ifdef CONFIG_PM_DEBUG
+int pm_test_level = TEST_NONE;
+
+static int suspend_test(int level)
+{
+        if (pm_test_level == level) {
+                printk(KERN_INFO "suspend debug: Waiting for 5 seconds.\n");
+                mdelay(5000);
+                return 1;
+        }
+        return 0;
+}
+
+static const char * const pm_tests[__TEST_AFTER_LAST] = {
+        [TEST_NONE] = "none",
+        [TEST_CORE] = "core",
+        [TEST_CPUS] = "processors",
+        [TEST_PLATFORM] = "platform",
+        [TEST_DEVICES] = "devices",
+        [TEST_FREEZER] = "freezer",
+};
+
+static ssize_t pm_test_show(struct kset *kset, char *buf)
+{
+        char *s = buf;
+        int level;
+
+        for (level = TEST_FIRST; level <= TEST_MAX; level++)
+                if (pm_tests[level]) {
+                        if (level == pm_test_level)
+                                s += sprintf(s, "[%s] ", pm_tests[level]);
+                        else
+                                s += sprintf(s, "%s ", pm_tests[level]);
+                }
+
+        if (s != buf)
+                /* convert the last space to a newline */
+                *(s-1) = '\n';
+
+        return (s - buf);
+}
+
+static ssize_t pm_test_store(struct kset *kset, const char *buf, size_t n)
+{
+        const char * const *s;
+        int level;
+        char *p;
+        int len;
+        int error = -EINVAL;
+
+        p = memchr(buf, '\n', n);
+        len = p ? p - buf : n;
+
+        mutex_lock(&pm_mutex);
+
+        level = TEST_FIRST;
+        for (s = &pm_tests[level]; level <= TEST_MAX; s++, level++)
+                if (*s && len == strlen(*s) && !strncmp(buf, *s, len)) {
+                        pm_test_level = level;
+                        error = 0;
+                        break;
+                }
+
+        mutex_unlock(&pm_mutex);
+
+        return error ? error : n;
+}
+
+power_attr(pm_test);
+#else /* !CONFIG_PM_DEBUG */
+static inline int suspend_test(int level) { return 0; }
+#endif /* !CONFIG_PM_DEBUG */
+
 #ifdef CONFIG_SUSPEND
 
 /* This is just an arbitrary number */
@@ -136,7 +209,10 @@ static int suspend_enter(suspend_state_t state)
                 printk(KERN_ERR "Some devices failed to power down\n");
                 goto Done;
         }
-        error = suspend_ops->enter(state);
+
+        if (!suspend_test(TEST_CORE))
+                error = suspend_ops->enter(state);
+
         device_power_up();
  Done:
         arch_suspend_enable_irqs();
@@ -167,16 +243,25 @@ int suspend_devices_and_enter(suspend_state_t state)
                 printk(KERN_ERR "Some devices failed to suspend\n");
                 goto Resume_console;
         }
+
+        if (suspend_test(TEST_DEVICES))
+                goto Resume_devices;
+
         if (suspend_ops->prepare) {
                 error = suspend_ops->prepare();
                 if (error)
                         goto Resume_devices;
         }
+
+        if (suspend_test(TEST_PLATFORM))
+                goto Finish;
+
         error = disable_nonboot_cpus();
-        if (!error)
+        if (!error && !suspend_test(TEST_CPUS))
                 suspend_enter(state);
 
         enable_nonboot_cpus();
+ Finish:
         if (suspend_ops->finish)
                 suspend_ops->finish();
  Resume_devices:
@@ -243,12 +328,17 @@ static int enter_state(suspend_state_t state)
         printk("done.\n");
 
         pr_debug("PM: Preparing system for %s sleep\n", pm_states[state]);
-        if ((error = suspend_prepare()))
+        error = suspend_prepare();
+        if (error)
                 goto Unlock;
 
+        if (suspend_test(TEST_FREEZER))
+                goto Finish;
+
         pr_debug("PM: Entering %s sleep\n", pm_states[state]);
         error = suspend_devices_and_enter(state);
 
+ Finish:
         pr_debug("PM: Finishing wakeup.\n");
         suspend_finish();
  Unlock:
@@ -369,18 +459,18 @@ pm_trace_store(struct kobject *kobj, struct kobj_attribute *attr,
 }
 
 power_attr(pm_trace);
+#endif /* CONFIG_PM_TRACE */
 
 static struct attribute * g[] = {
         &state_attr.attr,
+#ifdef CONFIG_PM_TRACE
         &pm_trace_attr.attr,
+#endif
+#ifdef CONFIG_PM_DEBUG
+        &pm_test_attr.attr,
+#endif
         NULL,
 };
-#else
-static struct attribute * g[] = {
-        &state_attr.attr,
-        NULL,
-};
-#endif /* CONFIG_PM_TRACE */
 
 static struct attribute_group attr_group = {
         .attrs = g,
diff --git a/kernel/power/power.h b/kernel/power/power.h
index c5321eb1f7c8..9f9e16e33962 100644
--- a/kernel/power/power.h
+++ b/kernel/power/power.h
@@ -188,3 +188,21 @@ int restore_highmem(void);
 static inline unsigned int count_highmem_pages(void) { return 0; }
 static inline int restore_highmem(void) { return 0; }
 #endif
+
+/*
+ * Suspend test levels
+ */
+enum {
+        /* keep first */
+        TEST_NONE,
+        TEST_CORE,
+        TEST_CPUS,
+        TEST_PLATFORM,
+        TEST_DEVICES,
+        TEST_FREEZER,
+        /* keep last */
+        __TEST_AFTER_LAST
+};
+
+#define TEST_FIRST      TEST_NONE
+#define TEST_MAX        (__TEST_AFTER_LAST - 1)