[PATCH] free_uid() locking improvement

Reduce lock hold times in free_uid().

Cc: Ingo Molnar <mingo@elte.hu>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 7 insertions, 3 deletions

diff --git a/kernel/user.c b/kernel/user.c
index d9deae43a9ab..2116642f42c6 100644
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -105,15 +105,19 @@ void free_uid(struct user_struct *up)
 {
         unsigned long flags;
 
+        if (!up)
+                return;
+
         local_irq_save(flags);
-        if (up && atomic_dec_and_lock(&up->__count, &uidhash_lock)) {
+        if (atomic_dec_and_lock(&up->__count, &uidhash_lock)) {
                 uid_hash_remove(up);
+                spin_unlock_irqrestore(&uidhash_lock, flags);
                 key_put(up->uid_keyring);
                 key_put(up->session_keyring);
                 kmem_cache_free(uid_cachep, up);
-                spin_unlock(&uidhash_lock);
+        } else {
+                local_irq_restore(flags);
         }
-        local_irq_restore(flags);
 }
 
 struct user_struct * alloc_uid(uid_t uid)