kernel/umh.c: optimize 'proc_cap_handler()'

If 'write' is 0, we can avoid a call to spin_lock/spin_unlock. Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Christophe JAILLET <[email protected]> Acked-by: Luis R. Rodriguez <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
XGWang0 · Nov 18, 2017 · 8c703d6 · 8c703d6
1 parent 4ca59b1
commit 8c703d6
Showing 1 changed file with 2 additions and 2 deletions.
diff --git a/kernel/umh.c b/kernel/umh.c
@@ -537,14 +537,14 @@ static int proc_cap_handler(struct ctl_table *table, int write,
 	/*
 	 * Drop everything not in the new_cap (but don't add things)
 	 */
-	spin_lock(&umh_sysctl_lock);
 	if (write) {
+		spin_lock(&umh_sysctl_lock);
 		if (table->data == CAP_BSET)
 			usermodehelper_bset = cap_intersect(usermodehelper_bset, new_cap);
 		if (table->data == CAP_PI)
 			usermodehelper_inheritable = cap_intersect(usermodehelper_inheritable, new_cap);
+		spin_unlock(&umh_sysctl_lock);
 	}
-	spin_unlock(&umh_sysctl_lock);
 
 	return 0;
 }