x86/itmt: Use guard() for itmt_update_mutex

Use guard() for itmt_update_mutex which avoids the extra mutex_unlock()
in the bailout and return paths.

Signed-off-by: K Prateek Nayak <kprateek.nayak@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com>
Link: https://lore.kernel.org/r/20241223043407.1611-3-kprateek.nayak@amd.com

arch/x86/kernel/itmt.c

@@ -44,12 +44,10 @@ static int sched_itmt_update_handler(const struct ctl_table *table, int write,
 	unsigned int old_sysctl;
 	int ret;
 
-	mutex_lock(&itmt_update_mutex);
+	guard(mutex)(&itmt_update_mutex);
 
-	if (!sched_itmt_capable) {
-		mutex_unlock(&itmt_update_mutex);
+	if (!sched_itmt_capable)
 		return -EINVAL;
-	}
 
 	old_sysctl = sysctl_sched_itmt_enabled;
 	ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
@@ -59,8 +57,6 @@ static int sched_itmt_update_handler(const struct ctl_table *table, int write,
 		rebuild_sched_domains();
 	}
 
-	mutex_unlock(&itmt_update_mutex);
-
 	return ret;
 }
 
@@ -97,18 +93,14 @@ static struct ctl_table_header *itmt_sysctl_header;
  */
 int sched_set_itmt_support(void)
 {
-	mutex_lock(&itmt_update_mutex);
+	guard(mutex)(&itmt_update_mutex);
 
-	if (sched_itmt_capable) {
-		mutex_unlock(&itmt_update_mutex);
+	if (sched_itmt_capable)
 		return 0;
-	}
 
 	itmt_sysctl_header = register_sysctl("kernel", itmt_kern_table);
-	if (!itmt_sysctl_header) {
-		mutex_unlock(&itmt_update_mutex);
+	if (!itmt_sysctl_header)
 		return -ENOMEM;
-	}
 
 	sched_itmt_capable = true;
 
@@ -117,8 +109,6 @@ int sched_set_itmt_support(void)
 	x86_topology_update = true;
 	rebuild_sched_domains();
 
-	mutex_unlock(&itmt_update_mutex);
-
 	return 0;
 }
 
@@ -134,12 +124,11 @@ int sched_set_itmt_support(void)
  */
 void sched_clear_itmt_support(void)
 {
-	mutex_lock(&itmt_update_mutex);
+	guard(mutex)(&itmt_update_mutex);
 
-	if (!sched_itmt_capable) {
-		mutex_unlock(&itmt_update_mutex);
+	if (!sched_itmt_capable)
 		return;
-	}
+
 	sched_itmt_capable = false;
 
 	if (itmt_sysctl_header) {
@@ -153,8 +142,6 @@ void sched_clear_itmt_support(void)
 		x86_topology_update = true;
 		rebuild_sched_domains();
 	}
-
-	mutex_unlock(&itmt_update_mutex);
 }
 
 int arch_asym_cpu_priority(int cpu)