Wrap variable with mutex

Valgrind's drd tool reported a race condition on a variable, so
mutex was added to wrap it. The chances of this causing a problem
are nill, but this makes it zero.

src/common/slurm_acct_gather.c

@@ -42,7 +42,8 @@
 #include "src/common/slurm_strcasestr.h"
 #include "src/common/xstring.h"
 
-bool acct_gather_suspended = false;
+static bool acct_gather_suspended = false;
+static pthread_mutex_t suspended_mutex = PTHREAD_MUTEX_INITIALIZER;
 
 static bool inited = 0;
 
@@ -244,10 +245,23 @@ extern int acct_gather_check_acct_freq_task(
 
 extern void acct_gather_suspend_poll(void)
 {
+	slurm_mutex_lock(&suspended_mutex);
 	acct_gather_suspended = true;
+	slurm_mutex_unlock(&suspended_mutex);
 }
 
 extern void acct_gather_resume_poll(void)
 {
+	slurm_mutex_lock(&suspended_mutex);
 	acct_gather_suspended = false;
+	slurm_mutex_unlock(&suspended_mutex);
+}
+
+extern bool acct_gather_suspend_test(void)
+{
+	bool rc;
+	slurm_mutex_lock(&suspended_mutex);
+	rc = acct_gather_suspended;
+	slurm_mutex_unlock(&suspended_mutex);
+	return rc;
 }

src/common/slurm_acct_gather.h

@@ -57,8 +57,6 @@
 #include "slurm_acct_gather_infiniband.h"
 #include "slurm_acct_gather_filesystem.h"
 
-extern bool acct_gather_suspended;
-
 extern int acct_gather_conf_init(void);
 extern int acct_gather_conf_destroy(void);
 
@@ -69,5 +67,6 @@ extern int acct_gather_check_acct_freq_task(
 	uint32_t job_mem_lim, char *acctg_freq);
 extern void acct_gather_suspend_poll(void);
 extern void acct_gather_resume_poll(void);
+extern bool acct_gather_suspend_test(void);
 
 #endif

src/common/slurm_acct_gather_profile.c

@@ -147,7 +147,7 @@ static void *_timer_thread(void *args)
 		now = time(NULL);
 
 		for (i=0; i<PROFILE_CNT; i++) {
-			if (acct_gather_suspended) {
+			if (acct_gather_suspend_test()) {
 				/* Handle suspended time as if it
 				 * didn't happen */
 				if (!acct_gather_profile_timer[i].freq)