[PATCH v2 06/10] PM: sleep: stats: Use locking in dpm_save_failed_dev()

["Rafael J. Wysocki" <rjw@rjwysocki.net>]

From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Because dpm_save_failed_dev() may be called simultaneously by multiple
failing device PM functions, the state of the suspend_stats fields
updated by it may become inconsistent.

Prevent that from happening by using a lock in dpm_save_failed_dev().

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Stanislaw Gruszka <stanislaw.gruszka@linux.intel.com>
---

v1 -> v2: Added R-by from Stanislaw.

---
 kernel/power/main.c |    5 +++++
 1 file changed, 5 insertions(+)

Index: linux-pm/kernel/power/main.c
===================================================================
--- linux-pm.orig/kernel/power/main.c
+++ linux-pm/kernel/power/main.c
@@ -325,13 +325,18 @@ struct suspend_stats {
 };
 
 static struct suspend_stats suspend_stats;
+static DEFINE_MUTEX(suspend_stats_lock);
 
 void dpm_save_failed_dev(const char *name)
 {
+	mutex_lock(&suspend_stats_lock);
+
 	strscpy(suspend_stats.failed_devs[suspend_stats.last_failed_dev],
 		name, sizeof(suspend_stats.failed_devs[0]));
 	suspend_stats.last_failed_dev++;
 	suspend_stats.last_failed_dev %= REC_FAILED_NUM;
+
+	mutex_unlock(&suspend_stats_lock);
 }
 
 void dpm_save_failed_step(enum suspend_stat_step step)