tracing: Switch trace_osnoise.c code over to use guard() and __free()

The osnoise_hotplug_workfn() grabs two mutexes and cpu_read_lock(). It has
various gotos to handle unlocking them. Switch them over to guard() and
let the compiler worry about it.

The osnoise_cpus_read() has a temporary mask_str allocated and there's
some gotos to make sure it gets freed on error paths. Switch that over to
__free() to let the compiler worry about it.

Cc: Masami Hiramatsu <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: https://lore.kernel.org/[email protected]
Signed-off-by: Steven Rostedt (Google) <[email protected]>

Author: rostedt

kernel/trace/trace_osnoise.c

@@ -2083,26 +2083,21 @@ static void osnoise_hotplug_workfn(struct work_struct *dummy)
 {
 	unsigned int cpu = smp_processor_id();
 
-	mutex_lock(&trace_types_lock);
+	guard(mutex)(&trace_types_lock);
 
 	if (!osnoise_has_registered_instances())
-		goto out_unlock_trace;
+		return;
 
-	mutex_lock(&interface_lock);
-	cpus_read_lock();
+	guard(mutex)(&interface_lock);
+	guard(cpus_read_lock)();
 
 	if (!cpu_online(cpu))
-		goto out_unlock;
+		return;
+
 	if (!cpumask_test_cpu(cpu, &osnoise_cpumask))
-		goto out_unlock;
+		return;
 
 	start_kthread(cpu);
-
-out_unlock:
-	cpus_read_unlock();
-	mutex_unlock(&interface_lock);
-out_unlock_trace:
-	mutex_unlock(&trace_types_lock);
 }
 
 static DECLARE_WORK(osnoise_hotplug_work, osnoise_hotplug_workfn);
@@ -2300,31 +2295,22 @@ static ssize_t
 osnoise_cpus_read(struct file *filp, char __user *ubuf, size_t count,
 		  loff_t *ppos)
 {
-	char *mask_str;
+	char *mask_str __free(kfree) = NULL;
 	int len;
 
-	mutex_lock(&interface_lock);
+	guard(mutex)(&interface_lock);
 
 	len = snprintf(NULL, 0, "%*pbl\n", cpumask_pr_args(&osnoise_cpumask)) + 1;
 	mask_str = kmalloc(len, GFP_KERNEL);
-	if (!mask_str) {
-		count = -ENOMEM;
-		goto out_unlock;
-	}
+	if (!mask_str)
+		return -ENOMEM;
 
 	len = snprintf(mask_str, len, "%*pbl\n", cpumask_pr_args(&osnoise_cpumask));
-	if (len >= count) {
-		count = -EINVAL;
-		goto out_free;
-	}
+	if (len >= count)
+		return -EINVAL;
 
 	count = simple_read_from_buffer(ubuf, count, ppos, mask_str, len);
 
-out_free:
-	kfree(mask_str);
-out_unlock:
-	mutex_unlock(&interface_lock);
-
 	return count;
 }