preemption_checks: avoid snprintf before checking error conditions

snprintf can cause hangs.  Move the string processing into the function so
that the string operations only occur when necessary after the conditions
have been checked.

Signed-off-by: Christoph Lameter <cl@linux.com>
Reported-by: Grygorii Strashko <grygorii.strashko@ti.com>
Tested-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

lib/smp_processor_id.c

@@ -7,7 +7,8 @@
 #include <linux/kallsyms.h>
 #include <linux/sched.h>
 
-notrace static unsigned int check_preemption_disabled(char *what)
+notrace static unsigned int check_preemption_disabled(const char *what1,
+							const char *what2)
 {
 	int this_cpu = raw_smp_processor_id();
 
@@ -38,8 +39,8 @@ notrace static unsigned int check_preemption_disabled(char *what)
 	if (!printk_ratelimit())
 		goto out_enable;
 
-	printk(KERN_ERR "BUG: using %s in preemptible [%08x] code: %s/%d\n",
-		what, preempt_count() - 1, current->comm, current->pid);
+	printk(KERN_ERR "BUG: using %s%s() in preemptible [%08x] code: %s/%d\n",
+		what1, what2, preempt_count() - 1, current->comm, current->pid);
 
 	print_symbol("caller is %s\n", (long)__builtin_return_address(0));
 	dump_stack();
@@ -52,15 +53,12 @@ notrace static unsigned int check_preemption_disabled(char *what)
 
 notrace unsigned int debug_smp_processor_id(void)
 {
-	return check_preemption_disabled("smp_processor_id()");
+	return check_preemption_disabled("smp_processor_id","");
 }
 EXPORT_SYMBOL(debug_smp_processor_id);
 
 notrace void __this_cpu_preempt_check(const char *op)
 {
-	char text[40];
-
-	snprintf(text, sizeof(text), "__this_cpu_%s()", op);
-	check_preemption_disabled(text);
+	check_preemption_disabled("__this_cpu_", op);
 }
 EXPORT_SYMBOL(__this_cpu_preempt_check);